Quality and Process control in PE and PP Manufacturing Separation Solutions for Plants and QC Contents

6 AN OVERVIEW:

NEWLY DEVELOPED RESINS ARE MORE CHALLENGING TO CONTROL IN PRODUCTION PLANTS 15 CRSYTEX® QC

18 APPLICATION NOTE: SOLUBLE FRACTION FOR PRODUCTION PLANTS

25 CRYSTEX® 42 29 GPC-QC

32 APPLICATION NOTE: GPC FOR PROCESS AND QUALITY CONTRON IN PE AND PP MANUFACTURING 39 INTRINSIC VISCOSITY ANALYZER, IVA

42 APPLICATION NOTE: INTRINSIC VISCOSITY DETERMINATION FOR POLYMERIC MATERIALS 49 UPCOMING INNOVATION: CEF QC 05 

SEPARATION SOLUTIONS FOR AMORPHOUS FRACTION PLANTS AND QC LABORATORIES CRYSTEX® QC

Complete automation of the Soluble Fraction measurement in polypropylene while quantifying the ethylene content and intrinsic viscosity in the whole sample, and the soluble and crystallyne fractions. Analysis of one sample at-a-time in approximately 2.5 hours (Page 15).

MOLAR MASS DISTRIBUTION

GPC-QC CRYSTEX® 42

Simplified and fully-automated GPC instrument for control This intrument shares the same analytical concept as laboratories in polyolefin production plants. Provides robust CRYSTEX® QC, but it uses a high-temperature autosampler and precise data for process with 42 positions, ideal for a central , where large control, in a simplified and automated wrokflow, for one batches of pelletized, more homogeneous samples need to sample at-a-time in 30 minutes (Page 29). be analyzed in sequence (Page 25).

INTRINSIC VISCOSITY CHEMICAL COMPOSITION DISTRIBUTION

IVA CEF QC (upcoming)

Fully-automated instrument for the Intrinsic Viscosity A simplified CEF for production plants to obtain the complete analysis of all polymeric materials, even the very challenging chemical composition distribution curve for one sample in ones that can require temperatures of up to 200ºC for less than 1h (incl. dissolution). The Density results facilitate dissolution. The autosampler allows up to 42 samples to be a direct correlation with traditional process controls. The sequentially analyzed without user intervention (Page 39). instrument can be operated as a CEF, TREF or TGIC (Page 49).

Quality Control for Polyolefins An Overview 07

Melt Index and density have not changed, so why is the “same” resin performing differently?

Will a competitor resin with the same Melt Index Composition Distribution (CCD) and thus, different and density perform equally? I am recycling performance and processing behavior. Once more, An Overview polyolefin resins. How can I optimize my product’s this shows that a separation technique is demanded performance? The resin I have used in the past is to have unequivocal characterization; in this case, now performing/processing differently. Why? using Temperature Rising Elution Fractionation (TREF), IS YOUR POLYOLEFIN RESIN PERFORMING AS EXPECTED? Crystallization Analysis Fractionation (CRYSTAF) or Within the (PE) family, the added Crystallization Elution Fractionation (CEF). information is essential, especially in the case of The introduction of single-site catalysts and the use of multiple reactors in dual reactor resins, as with pipe and blow molding the polyolefins industry has opened new routes to design resins with the products, or in the broad spectrum of linear low desirable microstructure to optimize performance in specific applications. density polyethylene (LLDPE) resins. While this is good news for manufacturing, it presents a greater challenge for quality control because the currently used parameters show only partial Figure 1 shows three different PE that, in spite of having information of the resin microstructure. the same Melt Index, they have completely different Molar Mass Distribution (MMD), and thus, completely Melt Index (MI) and density are common parameters in process control different performance and processing behavior. and product definition that represent average molar mass and average Fig 1. Three different resins with the same Melt Index but This reveals that a separation technique such as Gel completely different MWD and thus, different performance. composition respectively. However, with today’s sophisticated industrial Permeation-Size Exclusion (GPC/SEC) resins, these parameters are very far from defining resin performance. A set is needed to have unequivocal characterization of the of analytical techniques has been recently developed to detail additional resin chemical structure. These techniques, which in the parameters relevant to the resin performance. past demanded operation expertise and sophisticated equipment, are available today with simplified design for quality control purposes (GPC-QC). A similar situation is that of PE copolymers, such as the three LLDPE resins shown in Figure 2. They all have the same comonomer content, expressed with the density Fig 2. Three different PE resins with the same density but parameter, but reveal completely different Chemical completely different CCD and thus, different performance.

Quality Control for Polyolefins An Overview 09

Improving Performance by Fully Revealing the Resin Microstructure

Although MMD and CCD represent the most significant No Longer a Nice-to-have, Now a Must-have in The industry has also shown an increased interest and production of very high and Ultra High microstructural information, on occasions, this data Production Molar Mass (UHMW) resins in the last years. However, a full characterization of these resins is a alone is not enough due to the interdependence The increasing throughput of the new polyolefin challenging task and demands method and materials adaptation to prevent precipitation of the of molar mass and composition. A good example manufacturing plants and the incorporation of resin in the analytical process. The GPC-QC at low flow rate, has been developed to analyze the is that of Pipe resins, which contain small amounts complex multiple reactor-catalyst processes demand MMD of very high molar mass resins, one at a time. Additionally, a dedicated Intrinsic Viscosity of comonomer but for good performance, the a closer control of the microstructure to prevent Analyzer (IVA) was also designed to automatically analyze multiple samples of UHMW resins comonomer (branching) is required to be incorporated product variation with significant losses in off-grade through a capillary relative viscometer without memory effects or plugging. within the larger molecules. The analysis of branching production. The analysis of average properties such as at different molar masses can be today obtained MI, density, and amorphous fractions by rheological or in a quality control lab by a simplified but sensitive spectroscopic techniques, although important in stable GPC system with an additional IR composition sensor process conditions, on many occasions is not enough. (GPC-QC IR5). The measurement of the distributions by separation Within the Polypropylene (PP) family, the most techniques such as GPC-QC or CRYSTEX® QC is demanding structure is that of heterophasic or High- required. This is especially important during grade Impact Polypropylene (HIPP). The routine analysis changes, where reaching the desired microstructure in of the amorphous content (“xylene solubles”) is the shortest possible time is crucial to reduce off-grade important but the analysis of the ethylene content and production. Simplified separation techniques capable intrinsic viscosity in the two phases (crystalline and of obtaining results in short time are essential. amorphous) provides additional information that can be critical to optimize the product’s performance. All these parameters can now be obtained automatically with the new CRYSTEX® instrumentation based on a TREF (Temperature Rising Elution Fractionation) separation process (CRYSTEX® QC and CRYSTEX® 42).

Newly developed resins are increasingly challenging to control in production plants.

Quality Control for Polyolefins An Overview 11

Unparalleled Separation of the Soluble Fraction in PP

CRYSTEX® QC is a fully-automated instrument that The amorphous/crystalline fractions are quantified with a sensitive filter-type Infrared (IR) detector separates crystalline and amorphous fractions by that delivers equivalent values to the xylene solubles test, obtained with outstanding precision. means of a proprietary Temperature Rising Elution In addition, the IR detector measures the ethylene incorporation in the case of copolymers. The Fractionation (TREF) column where a small aliquot integration of a capillary viscometer provides an automated measurement of intrinsic viscosity of homogeneous solution is crystallized, in of the whole sample and both amorphous and crystalline fractions. di- or tri-chlorobenzene (o-DCB / TCB), on a support under reproducible and well-controlled conditions. Table 1 shows data obtained from seven replicate analyses using four grams of sample for a The polymer solution is loaded into the column at set of three polypropylene products with average standard deviations shown for each type of elevated temperature; it is crystallized to near ambient measurement. No additional experimental effort is required, since all the data is collected by temperature with no flow and then solvent is moved the IR and viscometer detectors during the automated analysis, with one equipment in a single through the column to elute the amorphous soluble 2-hour experiment. material towards the online detectors. Finally, the Soluble Fraction Crystalline Fraction Whole Sample column temperature is increased again to re-dissolve %weight Ethylene % Int. Visc.* Ethylene % Int. Visc.* Ethylene % Int. Visc.* the crystalline material which is eventually eluted to Sample A 4.06 14.8 0.96 3.4 2.74 4.2 2.86 the detectors. Sample B 2.73 16.3 0.90 3.9 2.33 4.4 2.30 Sample C 7.66 53.9 1.67 2.8 2.04 6.9 2.01 std 0.07 1.7 0.07 0.26 0.08 0.6 0.09 The analytical workflow is also very simple: all the *Intrinsic Viscosity measured with TCB at 165 analyst is required to do is put an approximate amount Table 1. Analysis of amorphous/crystalline fractions of three PP products by CRYSTEX® QC. of sample in a disposable bottle, place it in the stirred- heated plate, and lower a handle to pierce the bottle’s The GPC-QC instrument is built with the same single-sample dissolution station described septum with a needle (Figure 3). The automated Fig. 3 Safe and efficient operation of the single-sample above, and simplified hardware design including only one valve at high temperature, an external dissolution station in GPC-QC and CRYSTEX® QC instruments: process proceeds under computer control, including 1) Remove the previous bottle and place a new one with an HPLC pump and robust detectors, which help in achieving the required level of reliability and filling of the bottle with pre-heated solvent, controlling approximate sample weight; 2) Manual Injection and press minimizing potential downtime. The main detector is infrared, which provides a concentration START. the dissolution time, temperature and stirring and signal based on absorbance of total CH, being very appropriate for a QC environment thanks to taking an aliquot of the solution from the bottle into the fast stabilization time, stable baseline and good sensitivity. In addition, IR detection provides the instrument column. complementary information on chemical composition (short-chain branching, comonomer content) along the MMD.

Quality Control for Polyolefins amount ofaddedcomonomer. Thatbalance results second componentoflargermolarmasswithasmall component istypicallyproduced, togetherwitha reactor process. Alowermolarmasshigh-density bimodal high-densitypolyethylenemadeinadual- An applicationexampleisprovided inFigure 4fora day. controlled ataslowerpace, oneorseveraltimesper Once theprocess isstable, production mayneedtobe of reactors, or when achange of gradeisconducted. which isfoundappropriate forcontrolling thestart-up continuously withacycletimeofonehourorless, Following thisworkflow, theGPC-QCcanbeoperated the previous oneplacing the newoneinstation. bottle isprepared withitandtheanalystjustdiscards of interest. Whenanew samplecomesin,anew to generatetheMMDandanycalculatedparameters analysis isfinished,thechromatograms are processed according tothepre-set methodconditions.Oncethe started from thecomputer andproceeds automatically insert theneedlethrough theseptum. Theanalysisis station oven.Thentheanalystlowersahandleto disposable bottlewhichisplacedintothedissolution is received in the laboratory, it is weighed into a minimum manualwork.Whenasampleofpolymer The analytical workflow is quite simple and requires An Overview frequency ineachmolarmassrange. each ofthemodeswascalculatedfrom anaverageoftheSCB measured byGPC-QCforabimodalHDPE.Thedensityof Fig 4. properties (MIanddensity). methodsbasedonbulkenhanced overthealternative The levelofcontrol on the process isthus,greatly mass andtheweightfractionofeachcomponent. (based onmeasured SCB level),aswellthemolar the densitybeingproduced ineachofthetworeactors intervention, itispossibletoobtainanestimationon and in less than one hour with minimum operator for pipeapplications.From asingleGPC-QCanalysis, in enhancedmechanicalproperties, suchasESCR, dW/dLog M 0.00 0.10 0.20 0.30 0.40 0.50 and PPManufacturing and Process Control inPE GPC forQualityControl MMDandshortchainbranching(SCB)frequency 100 SCB MMD 1,000 0.940 g/cc 10,000 Molar mass(g/mol) 100,000 0.932 g/cc 1,000,000 10,000,000 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0

SCB/1000TC in DMF(N,N-dimethylformamide), PETpolyethylene analyzed inthissystem,includingPAN (polyacrylonitrile) Different polymersinvarioussolventshavebeen and tocontrol theproduction grades. IV ofpolymershasbeentraditionallyusedtospecify availability ofsuchmethodsinmanylaboratories,the of dilutesolutionviscositymeasurements andthe single-point estimationmethod.Duetothepopularity viscosity ofthepolymercanbecalculatedusinga a robust serialcapillaryviscometer. From it,theintrinsic reference tothepure solventismeasured bymeansof The relative viscosityofadilute polymersolutionwith polymeric materials,basedonthesameQCplatform. instrument fordeterminationofintrinsicviscosity Analyzer,The Intrinsic Viscosity IVA, is a dedicated process control /qualitycontrol tool. practical application in manufacturing plantsas a forward inthiskindoftechnology andenablesits even forthemostdifficult products. Thisisastep under nitrogen atmosphere, and lessthanonehour preparation stepwithan efficient dissolution process within 30minutesinmostcases,includingthesample open thedoortohigh-temperature GPCanalysis The optimizeddissolutionandseparationprocesses Quality Control for Polyolefins 13 Petro IndustryNews,April/May Issue2015 inPolymericMaterialsbyIVASolution Viscosity – September 2015 Control andQualityControl –TheColumn(LC/GC), Gel PermeationChromatography (GPC)forProcess Applications Notebook,December2013 (CRYSTEX Soluble fractionanalysisinpolypropylene forQC QC) –TheColumn(LC/GC),November2013 Automated SolublefractionanalysisinPP(CRYSTEX® References: (ISO 1628-3:2010f.i.)inallcases. IVA are ingoodagreement withreference methods o-DCB. Theintrinsicviscosityresults obtainedbythe (even highandultra-highmolarmass)inTCB in TCBaswellpolypropylene andpolyethylene terephthalate) inphenol/o-DCB,PLA(polylacticacid) Polymeric Materials forAllViscosity Measuring Intrinsic ® QC)LCGC–EUandNAThe 15

Soluble Fraction for Polyolefin Production Plants

CRYSTEX® QC

Quality Control for Polyolefins 17

RELIABLE AND AUTOMATED INSTRUMENT FOR SOLUBLE FRACTION DETERMINATION IN QUALITY CONTROL LABORATORIES OF POLYPROPYLENE PLANTS

CRYSTEX® QC is a step forward in technology for automating the Soluble Fraction determination in polypropylene and other polyolefin resins. This is a reliable instrument for continuous operation in the manufacturing plant laboratory, with minimum bench space and utilities requirements.

This is a modern alternative to the traditional wet chemistry method based on xylene solubility, known for being very time consuming and for requiring constant manual handling of solvent at high temperature. In comparison, CRYSTEX® QC is very easy to operate and obtains the amorphous phase content in a shorter time. It also eliminates the need to handle solvent manually and it operates with less flammable solvents than CRYSTEX® QC Xylene (TCB or oDCB), increasing the safety level in the laboratory. KEY FEATURES

The only manual task required is to put a representative amount of sample (up to 4g) in a disposable bottle, without the need of accurate weighing. The instrument then automates the entire analysis process, including precise dosing of solvent, sample Fully-automated analysis of the soluble (amorphous dissolution, separation of the soluble fraction from the crystalline matrix, and analysis by fraction) in polypropylene and other polyolefins. the online detectors. This whole process takes 2.5 hours. A sample can be analyzed every 2.5 hours (including dissolution) without manual operation. The crystalline and amorphous fractions are separated through a crystallization and re- dissolution temperature cycle within a proprietary TREF column. Precise quantification is No need for accurate weighing of sample or manual achieved by means of an infrared detector that also delivers ethylene content information. solvent handling. No external filtration or solvent evaporation required. Moreover, the instrument measures intrinsic viscosity by means of a built-in dual capillary viscometer. All results (concentration, ethylene content and intrinsic viscosity) are obtained Additional measurement of ethylene content and intrinsic viscosity for the amorphous fraction, the for the whole sample, the amorphous fraction, and the crystalline fraction. crystalline fraction, and whole sample.

For Process/QC laboratories in production plants.

Compatible with other polyolefin materials such as LDPE, and adaptable to other solubility tests (heptane or hexane solubles). CRYSTEX® QC APPLICATION NOTE 19

CRYSTEX® QC The Classic Gravimetric APPLICATION NOTE Procedure

Soluble Fraction Analysis in Polypropylene: (soluble fraction), the analysis of its molar mass and In addition to measuring the amorphous or soluble the equilibrium in the opposite direction provided a

Characterization of the whole polymer, ethylene content are of major importance in this type fraction percentage, CRYSTEX® QC quantifies the significant advantage over the extraction procedure: amorphous and crystalline fractions in a Quality of manufacturing process. ethylene incorporation and intrinsic viscosity in the The amorphous fraction did not have to migrate from Control Laboratory original sample and in both, the amorphous and the interior of the solid material to the surface, which Historically, the amorphous or soluble content has crystalline fractions. Total analysis time per sample is could be influenced by the size of the particles and Introduction been measured by solubility in xylene using manual wet approximately two hours. the molecular structure of the matrix. Solvent selection The analysis of the amorphous fraction in polypropylene chemistry methods, as described in the next section, was not so important in this procedure, and from a resins is considered a fundamental task in the production which demand significant manpower, solvent volume, Natta and coworkers (5) were among the first variety of solvents, xylene was chosen due to the ease of polypropylene; it provides a measurement of the and analysis time. Later on, it was shown that the to understand the importance of separating the of filtration of the crystallized polymer and ease of small amounts of undesirable low tacticity and low amorphous content in polypropylene can be measured polypropylene produced according to stereo regularity. drying. This procedure, which they named Fractional molar mass fractions in the homopolymer resins, which by crystallization (1) and a method was prepared based In those years (1950s) fractionation was only accessible Crystallization, resulted in a significant improvement have significant influence on the polymer properties on the Crystallization Analysis Fractionation (CRYSTAF) by extraction, using a Soxhlet apparatus with solvents in reproducibility over the extraction method and it and processing. The presence of amorphous fraction technique (2-4). of different boiling points. The atactic polymer was showed that separation was barely affected by molar is required for certain applications, as in the case of obtained by the extraction in boiling ether, the stereo mass or by the initial concentration in a rather broad high-impact polypropylene copolymer resins. The A new approach has now been developed to analyze block fraction corresponded to the material which range. incorporation of the amorphous material is usually done polypropylene samples, one at a time, in Quality Control was insoluble in boiling ether but soluble in boiling within the same production plant in a second stage of plant laboratories. CRYSTEX® QC consists on a fully heptane, and the isotactic fraction was what remained The Fractional Crystallization approach finally evolved the polymerization process by adding ethylene to the automated system based on a proprietary Temperature insoluble in those solvents. Most importantly in these into the current standard procedures (7-8) which can continuous reaction, which results in the formation of Rising Elution Fractionation (TREF) column where extraction procedures was the determination of the be summarized as follows: amorphous ethylene-propylene copolymer. a small aliquot of homogeneous polymer solution amorphous atactic fraction, although reproducibility “The polypropylene is dissolved in hot xylene, then is crystallized on a support under reproducible and was not as good as desired. cooled under controlled conditions down to 25ºC, The continuous measurement of the overall amount well-controlled conditions. The amorphous fraction which results in the precipitation of the insoluble of this rubbery fraction, which can range between 0 is measured with a highly sensitive filter-type Infrared A few years later (1960s), a new approach was fraction. The soluble matter remains in the xylene. The and 30% of the total polymer, is essential for plant (IR) detector delivering equivalent values to the xylene proposed by P.M. Kamath, L. Wild (6) and others, suspension is filtered and an aliquot of the solution control in order to obtain the desired specifications solubles measurement, obtained with outstanding by fully dissolving the sample in a good solvent and is then evaporated, dried and the residue weighed.” and performance of the polymer resin. In addition precision. allowing it to precipitate according to its crystallizability. (7-8) to the measurement of the total rubber percentage Carrying out the test in this manner and establishing

Quality Control for Polyolefins CRYSTEX® QC APPLICATION NOTE 21

The correlation with the classic gravimetric method was an approximate amount of sample into a bottle, excellent for a wide selection of PP resins as shown in placing the bottle in an oven, lowering a handle to Figure 3, while obtaining better reproducibility thanks pierce the bottle’s septum, and initiate the automated to the full automation of CRYSTEX®. run. There is no need of weighing the sample since the IR detection of the full solution will provide

An extension of the CRYSTEX® technique for application accurate measurement of the amount of resin used, Fig 1. Schematic representation of the analytical steps equired in the classic gravimetric method for the determination of the in quality control laboratories of polypropylene plants (which does not need to be in a dry form as residual xylene solubles. has now been developed. The new analytical process, water will not be detected by the IR). The IR detector

A schematic analytical process is depicted in Figure 1. appear to be of significant importance as the intention named CRYSTEX® QC, is based on TREF, rather than the is used to measure as well, the concentration of the This procedure, which we will refer to as the classic is to separate two different polymer phases quite apart CRYSTAF approach, with the intention of speeding up amorphous and crystalline fractions and their ethylene gravimetric method,has been extensively used in the in crystallinity as shown in Figure 2, where the soluble the analysis of a single sample while maintaining the incorporation. The crystallization in a TREF column, industry and has proven to be of great value to the fraction corresponds to the distinctive peak in a PP system’s same capability to measure intrinsic viscosity on an inert support, eliminates the filtration step, and manufacturing of polypropylene (PP). The analysis resin characterized by TREF or CRYSTAF analysis. and ethylene incorporation. The new method analyzes the integration of a capillary viscometer provides an of the xylene soluble with this approach however, one sample at a time and is capable to dissolve up to automated measurement of intrinsic viscosity of the demands significant manpower, solvent consumption, 4 g of sample, thus, minimizing error due to the poor whole sample and both amorphous and crystalline PP and an analysis time of around five to six hours. Just as TREF Analysis homogeneity of powder samples. fractions. significant is the fact that the precision of the method suffers from the required controlled precipitation The schematics of the system are presented in Figure conditions as discussed in the ASTM and ISO methods. 4. The only task done by the analyst consists in putting In the last years, new methods have been developed Amorphous Fraction to quantify the amorphous fraction attempting to overcome previous time-consuming procedures by automating the analytical process and, at the same T Visco. Correlation CRYSTEX - XS gravimetric method IR time, provide extended characterization of the Fig 2. Chemical Composition Distribution of a polypropylene 30 amorphous and crystalline phases. copolymer analyzed by TREF where the amorphous and TREF column in 25 crystalline fractions are well segregated. Micro Oven Dispenser

20 Automated Crystallization methods 15

The classic gravimetric method, as discussed above, In the early 2000s, it was shown that the amorphous Gravimetric 10 is based on a crystallization process where the content in polypropylene can be measured by an 5 crystalline matrix is segregated from the amorphous automated crystallization technique (1 ) and a method Solvent Waste 0 soluble fraction by cooling the solution according (CRYSTEX®) was developed based on CRYSTAF (2-4) 0 5 10 15 20 25 30 CRYSTEX Heated/stirrer plate to a specified method with a fixed crystallization using a chlorinated solvent (di or tri-chlorobenzene) temperature and time. The selection of solvent did not combined with the use of an IR detector. Fig 3. Correlation between the xylene solubles ISO/ASTM Fig 4. Schematic diagram of the new CRYSTEX® QC methods and the new crystallization approach. instrument.

Quality Control for Polyolefins CRYSTEX® QC APPLICATION NOTE 23

Automated Full analytical results are obtained in two hours, Ethylene content and intrinsic viscosity data along including not only the soluble fraction percentage, with their std values for the analysis of soluble and Crystallization but also the ethylene content and intrinsic viscosity crystalline fractions are shown in Table 2. It must be Methods of whole sample, as well as of the soluble and emphasized that no additional experimental effort crystalline fractions. Reproducibility in the soluble is required, since the data is collected by the IR and fraction percentage determination is remarkable; viscometer detectors during the automated analysis. typically standard deviation (std) is lower than 0.1%, The precision in ethylene content for the crystalline as seen in Table 1, much lower than indicated for the fraction is as good as for the whole sample, while for

A major advantage of this approach is that the to controlled ambient temperature, staying there standard gravimetric methods.(7) In the same Table, the amorphous fraction the standard deviation will crystallization step is done with a small but for an specified amount of time to precipitate the whole sample ethylene and intrinsic viscosity are also depend on the amount of soluble material. On the representative aliquot of the solution and takes place crystalline fraction; the column is then flushed to elute reported, along with standard deviation (std) values. other hand, the intrinsic viscosity is determined with in a packed column where the crystallization kinetics the amorphous soluble fraction peak (second peak in The precision achieved, also in those determinations, good precision for all the fractions. are fast and very well-controlled; thus, providing very Figure 5). The ratio of this peak area by the one of the proves the reliability of this method. reproducible results. The overall analytical process lasts whole sample provides the soluble percentage in the two hours including automated solvent dispensing into sample. As the soluble material passes through the IR Soluble Fraction Ethylene Content Intrinsic Viscosity* the bottle to dissolve the sample, and column cleaning and Viscometer detectors, the ethylene content and % std % std dL/g std Sample A 4.06 0.04 4.2 1.0 2.86 0.12 in order to be ready for the next sample analysis. intrinsic viscosity of this fraction are also measured. Sample B 2.73 0.05 4.4 0.4 2.30 0.04 d) Temperature is raised rapidly up to 160ºC with stop Sample C 7.66 0.12 6.9 0.3 2.01 0.12 Once the powder or pelletized polymer is put into the flow to re-dissolve the crystalline fraction and after a *Intrinsic Viscosity measured TCB at 165° bottle and the automated run is initiated, the analysis pre-set time of a few minutes, this fraction is eluted Table 1. Soluble fraction, total ethylene content and Intrinsic Viscosity for three different PP products. Data obtained from seven proceeds as follows: through both IR and viscometer detectors. replicate analyses using 4 g of sample. a) Filling the disposable bottle up to 100 or 200 mL e) The column is washed and the instrument remains with preheated solvent at 160ºC (depending on ready for a new sample analysis. Ethylene Content Intrinsic Viscosity* whether pellets or powder samples are analyzed) Soluble Fraction Crystalline Fraction Soluble Fraction Crystalline Fraction and initiate stirring. The deep vortex formed in the 1st load 2nd load % std % std dL/g std dL/g std dissolution process prevents the polymer from sticking Sample A 14.8 2.1 3.4 0.3 0.96 0.06 2.74 0.11 Dissolution Re-dissolution Sample B 16.3 1.5 3.9 0.2 0.90 0.11 2.33 0.02 to the glass walls and speeds up dissolution. Sample C 53.9 1.4 2.8 0.3 1.67 0.05 2.04 0.12 b) An aliquot of the solution is pumped through Whole Sample *Intrinsic Viscosity measured TCB at 165° Crystalline Fraction C2% the TREF column at 160ºC towards the detectors to Precipitation Non Sol. % [η]s C2% [η]s Table 2. Ethylene content and Intrinsic Viscosity in the amorphous/soluble and the crystalline fractions for three different PP measure the whole sample concentration, ethylene Soluble Fraction products. Same analysis as in Table 1. SF % C2% incorporated and intrinsic viscosity (first eluted peak [η]s in Figure 5). c) A new aliquot of the solution is injected into the middle of the column at 160ºC, the flow is stopped Whole Sample Soluble Fraction Crystalline Fraction and the column temperature is reduced rapidly down Fig 5. Schematic diagram of the new CRYSTEX@ QC instrument.

Quality Control for Polyolefins CRYSTEX® QC APPLICATION NOTE 25

Conclusions References CRYSTEX® QC is a new method to measure the 1) B. Monrabal , Encyclopedia of Analytical Chemistry, soluble fraction in polypropylene resins that has been John Wiley & Sons, 2000 pages 8074-8094. developed based on a TREF crystallization approach. 2) L. Romero, B. Monrabal, A. Ortín, Pittcon 2001 The analytical process is fully automated with no need U.S.A. of weighing, filtration or solvent handling. This new 3) A.. Ortín, B. Monrabal, M. D. Romero, LCGC method is especially interesting for quality control Vol 19 Issue Suppl., March 2006, 32. (product and process) in polypropylene plants. 4) A. Ortín, L. Romero, B. Monrabal. Polyolefin Characterization (ICPC) November 7 - 10, Shanghai, The total analysis time is two hours, and samples are China 2010 analyzed one at a time in disposable bottles. The total 5) G. Natta et al. Chim. e Ind. (Milano) 39, 275, 1957 volume consumption is as low as 180 mL for a 2-g 6) P.M. Kamath and L. Wild, Polymer Engineering & sample analysis. The analysis of 4 g of resin in the Science, 6, Issue 3, 213–216, 1966 form of powder can be done for enhanced sample 7) ASTM standard D5492-10, ASTM representativeness. 8) ISO standard 6427, 1992, ISO standard 16152, 2005

Besides the soluble fraction (equivalent to xylene solubles), CRYSTEX® QC measures automatically and simultaneously, the ethylene content and intrinsic viscosity in both amorphous and crystalline fractions, and in the whole sample.

The possibility to measure a sample in two hours allows ® a fast response in process control during product grade CRYSTEX 42 changes reducing off grade production. The new system can be used with other polyolefin type resins as well.

Quality Control for Polyolefins 27

HIGH-THROUGHPUT SYSTEM FOR SIMULTANEOUS MEASUREMENT OF THE SOLUBLE FRACTION, ETHYLENE CONTENT AND INTRINSIC VISCOSITY

CRYSTEX® 42 is a high-throughput and fully-automated approach for obtaining the soluble fraction in polypropylene and other polyolefin resins. It is based on the same TREF separation concept as CRYSTEX® QC, in which the sample is loaded into a TREF column twice. The first injection serves to measure the whole polymer and the second one remains within the column for a crystallization ramp that results in the separation of the soluble from the crystalline fraction.

CRYSTEX® 42 incorporates a high temperature autosampler with 42 positions to analyze samples in 20mL vials (max. sample amount of 160mg). This system eliminates the need to handle solvent manually and it operates with less flammable solvents than Xylene CRYSTEX® 42 (TCB or oDCB), increasing the safety level in the laboratory. KEY FEATURES

Results are very precise thanks to its full automation and to its integrated infrared detector (IR4), which measures precisely the amount of sample analysed as well as providing ethylene content information. Moreover, for a truly complete analysis, the Fully-automated analysis of the soluble fraction in instrument measures intrinsic viscosity by means of a built-in dual capillary viscometer. polypropylene and other polyolefins. All results (concentration, ethylene content, and intrinsic viscosity) are obtained for the Additional analysis of ethylene content and intrinsic whole sample, the soluble fraction, and the crystalline fraction. viscosity for the amorphous fraction, the crystalline fraction and whole sample.

While CRYSTEX® QC was designed to be installed in each production plant to monitor Fully-automated process for 42 samples: No need in real time the process analyzing a significant amount of powder sample (up to 4g), for accurate weighing of the sample or manual solvent handling. No external filtration and no solvent CRYSTEX® 42, thanks to the incorporation of the high temperature autosampler, evaporation required. becomes a perfect complement to be used in a central lab, where large batches of Dissolution and full analysis of the first sample pelletized, more homogeneous samples need to be analyzed. completed in 3 hours. Following samples results are obtained every 2 hours.

Compatible with other polyolefin materials such as LDPE and adaptable to other solubility tests (heptane or hexane solubles). 29

HT GPC for Process Control and Quality Control in PE and PP Production

GPC-QC

Quality Control for Polyolefins 31

SIMPLIFIED AND FULLY-AUTOMATED HIGH-TEMPERATURE GPC INSTRUMENT AIMED AT CONTROL LABORATORIES IN THE POLYOLEFIN INDUSTRY

GPC-QC is a compact, high-temperature GPC instrument for quality control in polyolefin manufacturing lines. The instrument has a simple and reliable approach based on Polymer Char’s recently developed QC platform, to provide robust and precise Molar Mass Distribution for process control.

For quality control purposes, the industry has traditionally relied on physical parameters related to an average of the MMD, such as melt flow index (MFI) and density. These parameters are not enough when producing complex multiple reaction products, some of them having multimodal MMD. It is in these occasions when GPC-QC can provide significant value by measuring the whole MMD. GPC-QC KEY FEATURES GPC-QC delivers the complete Molar Mass Distribution for one sample through a simplified workflow, while keeping a fully automated sample preparation and an analysis free of manual solvent handling throughout the entire process. The complete analysis takes 30 minutes including dissolution. Full automation of the entire analytical process.

The IR detection, implemented in the instrument through Polymer Char’s integrated One sample analyzed in 30 minutes including dissolution. IR4 or IR5 MCT detectors, is highly stable, contributing to the overall reliability of the instrument. The IR detector also provides simultaneous chemical composition IR4 or IR5 MCT detectors for Concentration and Short Chain Branching information. information, which is key for controlling the production of heterogeneous resins.

Optional incorporation of a dual-capillary viscometer. Moreover, for a truly complete analysis, the instrument can also measure intrinsic Simple and reliable design for Quality Control viscosity by means of a built-in dual capillary viscometer that can be incorporated as an environments. additional feature. Comprehensive results (MMD, SCB, IVD).

Outstanding precision thanks to the full automation and the detectors’ robustness. GPC-QC APPLICATION NOTE 33

GPC-QC Design Principles and Operation APPLICATION NOTE

Introduction complexes around the world. Even if the material being Gel permeation chromatography (GPC/SEC) A simplified hardware design including only one Polyolefin (PO) constitutes the largest volume produced is in fact characterized by a distribution is extensively used in the industry’s analytical valve at high temperature, an external HPLC pump industrial polymer group in the world in terms of of molar masses (MMD) and possibly a distribution laboratories to obtain the MMD. The requirement and robust detectors, helps in achieving the required economic impact and production. They are used for of chemical compositions (CCD), due to historical of high temperature operation, given the semi- level of reliability and minimizing potential downtime. making a wide range of commercial products that and practical reasons, the production is typically crystalline nature of polyolefin, together with the The main detector is infrared, which provides a touch nearly every aspect of our daily lives, such as controlled based on bulk properties, which can be inherent complexity of the technique and fragility of concentration signal based on absorbance of total CH, automobile parts, pipes, packaging films, household measured with relatively simple equipment. Melt flow columns, has prevented in the past the availability of being very appropriate for the QC environment thanks bottles, and many more. PO as a group includes high- rate (MFI) is maybe the most important of such bulk MMD analysis as a routine process control tool in the to the fast stabilization time, stable baseline and good density and low-density polyethylene (HDPE, LDPE), parameters, being related mainly to the average molar manufacturing plant laboratory. In order to fulfill this sensitivity. polypropylene (PP), ethylene-propylene (EP) rubber, mass. Density, which is more related to the average of need in the industry, a compact GPC-QC instrument and linear low density (LLDPE) copolymers of ethylene chemical compositions, is another parameter typically has been developed to provide robust and precise Depending on the process homogeneity, a significant with alpha olefins (propylene, 1-butene, 1-hexene, used for controlling the reactor and the product. MMD data for process control. In addition to a high- amount of sample may be required to obtain a good 1-octene). They are poly-disperse materials, meaning reliability hardware design, the operation workflow representativeness, so large capacity vials of 100 or that a single product is made of a range of chains with With the development of more complex PO, such a has been simplified while keeping full automation of 200 mL are used compared to the typical 2 – 10 mL different chain-lengths and possibly different chemical multimodal polyethylene or heterophasic PP, and sample dissolution and analysis. used in research grade instruments. Up to 200 mg of compositions when more than one monomer type is the requirement for a more uniform production and polymer can be dissolved for analysis, although 50 mg used in the synthesis. Moreover, different molecular tighter specification ranges demanded by a global Given that the application for GPC-QC follows the is the typical sample size. architectures (linear or branched) and stereo-structures and competitive market, the classical approach of process changes in manufacturing, there are no (tacticity in PP) are also possible in these products. All relying on bulk physical properties for control of the batches of samples coming together to be analyzed. The analytical workflow is quite simple and requires that complexity, together with the semi-crystalline manufacturing process starts to find its limits. A new Instead, the analysis of a single sample of the minimum manual work. When a sample of polymer is nature of most PO materials, helps to understand the paradigm needs to be implemented based on acquiring material produced at a particular time is required, received in the laboratory, it is weighed into the vial expanding application range of these products. complete information about the full distributions in a continuous operation cycle. That means there is and a small magnetic bar is placed (a small amount of that characterize the products, in order to replace no need for an auto-sampler, but a single dissolution a flow rate marker, or internal standard, can be added A range of reactor configurations and catalyst systems or complement the control based on single average station optimized to shorten the dissolution time to the vial). The vial is placed in the dissolution station are used nowadays by different manufacturers to parameters. is used instead. This is a fundamental difference in oven. Then the analyst lowers a handle to insert the produce thousands of tons of polyethylene and the design for QC, compared to the instrumentation needle into the vial through the septum. polypropylene every year, in huge dedicated to research.

Quality Control for Polyolefins GPC-QC APPLICATION NOTE 35

Results and filling volume was set to 80 mL taken from the injection Mw (g/mol) Mn (g/mol) Mw / Mn same reservoir as the mobile phase, dissolution time 15-0365 190,158 46,638 4.08

and Discussion was 60 minutes at 160ºC with 400 rpm stirring. The 15-0364 189,939 47,122 4.03

IR detector concentration chromatograms are shown 15-0363 189,840 46,936 4.04

in Figure 1 (left) for the seven replicates, which overlay 15-0362 190,592 47,155 4.04

perfectly. It should also be noted that the separation 15-0361 191,754 47,057 4.07 was achieved in a time slightly over 2 minutes. The 15-0360 190,258 47,335 4.02 total analysis time can be reduced to around 3 minutes, 15-0359 190,630 47,622 4.00

The analysis is started from the computer, and Precision in the molar mass results is key in the and solvent consumption to around 50 mL per sample. average 190,453 47,124 4.04 proceeds automatically according to the pre set application of this technology in manufacturing std 647 308 0.03 RSD (%) 0.34% 0.65% 0.68% method conditions. Once the analysis is finished, the control, so some experiments were conducted to The good precision in the collected chromatograms is chromatograms are processed to generate the MMD assess whether the performance was satisfactory. translated to the calculated MMD as seen in the same Table 1. Summary of molar mass averages and poly-dispersity index showing excellent precision obtained by GPC-QC. and any calculated parameters of interest. When a A series of replicate analyses of an LLDPE material Figure (right). The molar mass averages Mw and Mn new sample comes in, a new vial is prepared with it (density 0.868 g/cm3) were performed in a GPC-QC from all individual distributions are presented in Table and the analyst just discards the previous one placing instrument, using typical analysis conditions: mobile 1, together with the poly-dispersity index calculated vigorous stirring. Besides that, the vial is filled with preheated solvent, so no additional time is required the new one in the station. Following this workflow, phase was 1,2,4-trichlorobenzene (TCB) with 300 as the ratio Mw/Mn. This index is related to the the GPC-QC can be operated continuously with a cycle ppm of butylhydroxytoluene (BHT) as antioxidant, broadness of the distribution, and that information is to increase its temperature once in the vial. The time of one hour or less, which is found appropriate chromatographic pump flow rate of 2.0mL/min, not available when only bulk properties are measured. optimized dissolution and separation processes opens for controlling the start-up of reactors, or when a column and detectors temperature 150ºC, injection The precision in the molar mass averages and poly- the door to HT-GPC analysis within 30 minutes in most change of grade is conducted. Once the process is 200 μL, and the column was a PL Rapide H 150 x dispersity index expressed as standard deviation (std) cases, including the sample preparation step, and less stable, production may need to be controlled at a 7.5 mm (Agilent, Waldbronn, ). For sample and relative standard deviation (RSD %) is remarkable than one hour even for the most difficult products. slower pace, several times per day. preparation, 40 mg of polymer were put in the vial for GPC analysis. This means a breakthrough in this kind of technology and enables the practical application in manufacturing

For the implementation of this new technology in plants as a process control /quality control tool. a) b) manufacturing plants for process control, the total 1.0 Additional detection to enhance the information 15-0365 15-0365 cycle time, from sample reception to delivery of results, 15-0364 15-0364 0.090 gained by GPC-QC: chemical composition by IR 15-0363 0.8 15-0363 15-0362 is a crucial parameter. Thanks to the use of a single 15-0362 0.070 15-0361 and viscometry 15-0360 15-0361 fast-GPC column and increased pump flow rate, the 15-0359 0.6 15-0360 The use of an IR detector in these instruments can 0.050 15-0359 actual GPC separation is performed in less than three also generate useful information on the chemical dW/dLogM 0.4 0.030 min. However, the polymer needs to be brought in composition of the sample being analyzed. This is

IR Absorbance 0.2 solution before analysis, which in the case of most PO, 0.010 relevant in the case of copolymers, which account for it is considered a time-consuming process. 0.0 -0.010 0.00 1.00 2.00 3.00 4.00 100 1,000 10,000 100,000 1,000,000 a large part of the PO produced nowadays, such as The single-vial dissolution station in the GPC-QC was Retention time (min) Molar Mass (g/mol) LLDPE, some HDPE and also the important group of EP optimized in order to shorten the dissolution time, by Fig. 1. Chromatograms (left) and molar mass distribution (right) for seven injections of a PE sample, showing excellent precision copolymers. ensuring good heat-transfer to the vial and providing in the injection and analysis process in GPC-QC. Smaller peak at 2.6 min is a flow rate marker.

Quality Control for Polyolefins the weightfractionofeachcomponent.Thelevel of thetworeactors, aswell asthemolarmassand an estimationonthedensitybeingproduced ineach minimum operatorintervention,itispossibletoobtain GPC-QC analysis, and in inlessthanone hour with such asESCR,forpipeapplications.From asingle balance results inenhanced mechanicalproperties, mass withasmallamountofaddedcomonomer. That together withasecondcomponentofhighermolar mass high-density component is typically produced, HDPE madeinadual-reactor process. Alowermolar An exampleisprovided inFigure 2forabimodal heterogeneous multicomponentresins. mass distributioncanalsobemeasured inthecaseof be reported, butpossiblevariationsalongthemolar value representing the bulk composition/density can to density units for a given product range. A single translated toeithercomonomerweightfractionor The informationgeneratedbytheIRdetectorcanbe frequency ineachmolarmassrange. each ofthemodeswascalculatedfrom anaverageoftheSCB measured byGPC-QCforabimodalHDPE.Thedensityof Fig. 2. dW/dLog M 0.00 0.10 0.20 0.30 0.40 0.50 100 MMD andshortchainbranching(SCB)frequency SCB MMD 1,000 0.940 g/cc 10,000 Molar mass(g/mol) 100,000 0.932 g/cc 1,000,000 10,000,000 GPC-QC APPLICATION NOTE 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0

SCB/1000TC reliability ofGPC-QCasaprocess control tool. as a means to enhance the precision and long-term based onviscositydistribution,are beingdeveloped range. Additionally, robust dataprocessing methods, developed, targetedtoagivenprocess orproduct based onmultivariateanalysisormodelingmaybe this technology, specificdataprocessing procedures, used nowadays.Inorder to optimizetheapplicationof detailed informationthanthebulkproperty methods a GPCseparation,itprovides enhancedandmore for process control andQC,giventhatbymeansof It canbesaidthatGPC-QCisaverypowerfultool this environment. design used in GPC-QC is robust and well suited for tomolarmass.The2-capillaryserialas analternative the polymerandsoitmaybepreferred insomecases related totheprocessing behaviorandproperties of chain branching.Intrinsicviscosityismore directly intrinsic viscosityanditsdistribution,alsoonlong included inGPC-QCtocollectdataonthepolymer When required, a2-capillaryserialviscometercanbe products withknownchemicalcomposition. calibration canbeusedwithasmallsetofreference to obtainquantitativeresults from theIR,asimple deliver itwithoutanyanalyticalcomplexity. Inorder QC technology, giventhatthebuilt-inIRdetectorcan All thatcapabilityisreadily availableusingtheGPC- and density). methodsbasedonbulkpropertiesthe alternative (MI control ontheprocess isthusgreatly enhancedover control requirements. to around 30minutes,well inlinewiththeprocess including thesampledissolutionstepcanbereduced developed. It has been proved that the total cycle time, MMD inamanufacturingplantlaboratoryhasbeen Instrumentation specificallyaimedatmeasuringthe (MMD). information givenbythemolarmassdistribution the product canberealized byusingmore complete An enhanced,more refined, control ontheprocess and which isquitelimitedinformationontheproduct itself. properties ofthebulkmaterial(MeltIndex,density), and PPisnowadaysstillbasedonmeasuringphysical The control ofthereactors formanufacturingof PE Conclusions Overlay of5injections MMD andSCBresultsofabimodalHDPEsample

dW/dLog M 0.10 0.00 0.05 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 2.0 3.0 4.0 Log M 5.0 6.0 Quality Control for Polyolefins 7.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0

SCB/1000TC 37 · Processorslaboratories · Monitoringthemicrostructureofpiperesins processes · Monitoringgradechangesinmulti-reactor · Plantstart-ups · Pilotplants Important applicationsforGPC-QCare: can alsobeincorporated. by thebuilt-inIRdetector, whileanonlineviscometer composition, which can be related to density, is given (RSD around 0.5%).Additionaldetectionofchemical both averagemolarmassandpoly-dispersityindex Reproducibility ofthistechnologyisverygoodin for GPC-QC Applications Important Dissolution M w d=0.940 g/cm Polyethylene =200,000 g/moL 3 39

Intrinsic Viscosity Determination for Polymeric Materials

IVA

Quality Control for Polyolefins 41

FULLY-AUTOMATED INSTRUMENT FOR DETERMINATION OF INTRINSIC VISCOSITY IN POLYMERIC MATERIALS

A reliable and automated instrument for intrinsic viscosity analysis of polymeric materials in solution. Intrinsic viscosity can be seen as an indirect measurement of the average molar mass and, as a result, it provides valuable information within any process.

IVA integrates in a reduced footprint, a robust dual-capillary relative viscometer combined with a high temperature autosampler with a capacity for 42 samples. IVA can analyze a wide range of with IV values from 0.5dL/g up to over 40dL/g, such as polyolefins, PET, PAN, PMMA, and others, by using almost any organic solvent.

The principle of a relative viscometer is simple: the pressure-drop across a stainless- steel capillary tubing caused by the flow of polymer solution is compared to the one produced by the solvent, which is measured simultaneously by a twin reference capillary. The relative viscosity of polymer solution is derived from the ratio of pressure, and the intrinsic viscosity is calculated taking into account the injected mass. IVA KEY FEATURES

Unlike the glass capillaries used in Ubbelohde viscometers, the IVA capillaries and tubing do not require manual washing or rinsing, and provide robust and precise viscosity values over time.

Full-automation of dissolution and analysis processes. When using IVA, the analyst places the vials with polymer into the autosampler’s No manual solvent handling. external tray, where they stay at room temperature until they are scheduled for analysis under software control. Then the instrument takes the vials into the dissolution oven, High temperature autosampler for dissolution of samples in the same instrument. fills them with solvent and starts shaking. Dissolution temperature, shaking intensity, non-oxidative atmosphere with nitrogen, and time are accurately controlled so that the Self-cleaning design based on dual capillary relative analyst can select the optimum conditions to achieve full dissolution while minimizing viscometer. thermal degradation. High precision achieved by automation.

Up to 42 samples can be analyzed sequentially. The analysis of polyolefins and other polymers containing significant C-H content can be further improved by the incorporation of the optional Infrared detector IR4 to Analysis of high and ultrahigh molar mass polymers. accurately quantify the injected polymer mass, which results in improved precision and Compatible with most organic solvents such accuracy of intrinsic viscosity determination. as decalin, chloroform, tetrahydrofuran, tri- chlorobenzene, and others. IVA APPLICATION NOTE 43

IVA APPLICATION NOTE

New research leads to the development of an used organic solvents such as decalin, tetralin, tri- Absolute viscosity of fluids is important to many The intrinsic viscosity has units of inverse density (dL/g automated and versatile technique for solution chlorobenzene (TCB) and ortho-dichlorobenzene industries and can be measured using different types for instance). It is defined at the limit of infinite dilution viscosity determination of a wide range of among many others. Dissolution temperature and viscometers. However, in polymeric materials the (zero concentration), and sometimes calculated by polymeric materials in different solvents, from analysis temperature can be set independently, from interest is on the relative viscosity of a dilute polymer extrapolation of data at different concentration levels. ambient temperature up to 200ºC. ambient to 200ºC, so that a wide range of polymers, solution compared to that of the pure solvent, given A more practical and efficient approach is based on even the most crystalline ones, can be analyzed with that from it, the intrinsic viscosity, related to molar a single-point relative viscosity measurement, taken Introduction convenience and safety with this alternative approach. mass of the polymeric material, can be derived. In the at a defined concentration low enough to eliminate

The determination of the solution viscosity of first place, the relative viscosity η[ rel] is defined as: the need for extrapolation, or using a model equation polymeric materials is very important to the industry, Intrinsic Viscosity Determination to estimate the extrapolated value. Among several both to research and manufacturing, since it can be The proposed new method performs the polymer models and equations, the Solomon-Ciutà Equation, used to estimate the molar mass, providing important intrinsic viscosity measurement by means of a two- which does not require additional parameters, can be information relating to the physical properties of capillary relative viscosity detector, which concept used: polymers. The relative viscosity of a dilute polymer was developed and patented by Yau in the 80s This is a dimensionless quantity which represents to solution to that of the pure solvent itself is measured (US 4,793,174), as a robust method in contrast to what extent the added polymeric material increases and from it, the intrinsic viscosity (IV or [η]) of the temperature, pressure or solvent flow rate variations. the viscosity of the solvent. The relative viscosity of the polymer is calculated. Due to the popularity of dilute solution is proportional to the amount or concentration A serial viscometer design has been implemented solution viscosity measurements and the availability of Capillary viscometers rely on the principle that under (C) of polymer it contains, while the intrinsic viscosity for the new method: two pieces of capillary tubing those methods in many manufacturing laboratories, a forced flow (Q), the pressure drop ∆P( ) due to a is independent of concentration. The specific viscosity are connected in series in such a way that the first the IV of polymers has been traditionally used to specify fluid traveling along a capillary tubing of lengthL and [ηsp] of the solution and the polymer intrinsic viscosity one experiments the flow of pure solvent while the and to control the production grades. It must be noted radius r, is proportional to the absolute viscosity of the [η] are calculated according to the Equations: second one simultaneously receives the flow of the however, that IV is not a property of the polymer itself, flowing fluidη [ ], according to Poiseuille’s law: dilute polymer solution. The pressure drop across as molar mass is, but rather a property of the polymer each capillary is measured continuously as a function solution, influenced by the solvent and temperature. of time by high sensitivity differential pressure transducers. According to Equations (1) and (2), The recently developed technique is an automated the relative viscosity is proportional to the ratio of process for viscosity measurements of polymeric differential pressures, being independent of the flow materials in solution. It is compatible with typically rate. An instrumental constant is easily measured by

Quality Control for Polyolefins IVA APPLICATION NOTE 45

Results and Applications

flowing pure solvent through the two capillaries. The solvent is added to the vials, controlling the dissolution Different polymers in various solvents have been A factor to keep in mind when comparing different constant is automatically measured with every injection time per vial, injecting each solution and rinsing of the analyzed in this system, including PAN (polyacrylonitrile) methods to evaluate IV in polymeric materials is the thus, compensating for small, long-term variations capillary lines. The solution travels safely throughout in DMF (N,N-dimethylformamide), PET in phenol:o- effect of shear rate on the observed viscosity. Methods in capillaries (self-calibrating). It also accounts for all the system without any risk of precipitation because DCB, PLA in TCB as well as polyolefins in TCB and based on glass capillaries are driven by gravity and differences in tubing dimensions, so in this design, there are no cold spots. A new run can be immediately o-DCB. Even if the procedure or conditions in this new operate under low shear condition, while forced flow, it is not required that the capillaries stay accurately started after finishing the previous one, achieving a system were different, the IV results obtained were in used in this new method, may work at higher shear matched. throughput of 40 samples a day in standard operation good agreement with reference methods (ISO 1628- rates. Typically when shear rate increases the observed conditions. 3:2010 f.i.) in all cases, as shown in Figures 1 and 2 for viscosity decreases, so keeping constant shear rate may The relative viscosity is calculated as a function of two of the systems considered. be advantageous in order to get consistent results. time as the injected solution goes through the system, In order to maintain the polymeric sample integrity 1.20 4.50 and any influence of flow-rate variations (such as along the dissolution and measurement processes, 4.00 high frequency pump pulsations) or thermal effects Sample Care protocols have been implemented as part 1.00 3.50 are cancelled out directly by the reference capillary, of the method. Those include the ability to purge the C (dL/g) 0.80 ° 3.00 resulting in very high sensitivity and long-term stability. vial atmosphere with an inert gas (Nitrogen) before C (dL/g) ° 2.50 dissolution starts, and controlling accurately the time 0.60 2.00 An automated technique for Intrinsic Viscosity spent at high temperature by keeping every vial inside 0.40 1.50 y= 0.8230x Analysis of the oven only for the programmed dissolution R2= 0.9989 Glass capillary @25 y= 1.161x R2= 0.995 1.00 The proposed method constitutes a precise and time. The vials remain in an external tray at room

0.20 ISO 1628-3:2010 decalin @135 0.50 convenient approach to IV measurement, due to the temperature until the scheduling software requests 0.00 0.00 automation of all the analytical procedures, from their transfer to the dissolution oven. Efficient heat 0.00 1.00 2.00 3.00 4.00 5.00 0.00 0.20 0.40 0.60 0.80 1.00 filling of vials to the reporting of results. Samples are transfer to the vial, together with preheating of the IVA method, 35°C (dL/g) IVA method, TCB @150°C (dL/g) put in solid form into 20 mL vials and brought to an solvent prior to delivery to the vial, help in shortening Fig. 1. Correlation of intrinsic viscosity (IV) values obtained Fig. 2. Correlation of intrinsic viscosity (IV) values obtained autosampler tray with capacity of 42 vials. The operator the time required for dissolution. Oxidative and using the IVA method compared to IV determined using a using the IVA method compared to IV determined enters the samples identification data, selects the thermal degradation is thus minimized, ensuring that traditional glass capillary setup for a set of PET samples. In according to standard method ISO 1628-3:2010 for a set of both cases a mixture of phenol:o-DCB (2:3, m:v) was used polypropylene samples. IVA was run in tri-chlorobenzene at analytical method and starts the analysis that proceeds accurate intrinsic viscosity is measured even for the while temperatures were 35ºC and 25ºC respectively. 150ºC, using solutions prepared at 1 mg/mL; the ISO method unattended until all the vials defined in the instrument most challenging ultra-high molar mass materials, or was performed in decalin at 135ºC with solutions at 1-1.5 mg/mL The linear correlation is excellent as proved by the run queue are analyzed. Under software control, oxidation-prone polymers, such as polypropylene. high R2 value.

Quality Control for Polyolefins IVA APPLICATION NOTE 47

A study was conducted for a set of PE materials Dissolution temperature and time must be chosen A technique that is spanning a very wide range in IV, in order to compare so that the polymer dissolves completely but also to the observed viscosity at two different flow rates. give the very long molecular chains enough time to proven to be efficient, Results depicted in Figure 3 show that an excellent disentangle completely and obtain reliable viscosity precise, and safe correlation was found, and therefore a high flow rate values. In Figure 4, data collected after 90 minutes or determination can be performed in order to reduce 180 minutes of dissolution show that longer time is the analysis time, and still obtain data comparable to required to achieve that full disentanglement condition; lower shear conditions. The analysis time per sample otherwise, the intrinsic viscosity is underestimated. was reduced from half an hour to 4 minutes with the When the polymer stays at elevated temperature for In order to demonstrate the advantage in precision Conclusions increased flow rate. such long time, a nitrogen atmosphere is also required when applying online IR quantification compared to A new technique has been developed for dilute solution to prevent oxidative degradation which also decreases the offline balance, three different high molar mass PE viscosity that is proven to be efficient, precise and safe. 30.00 the observed viscosity a seen in the same Figure 4. materials were analyzed at a low concentration level A wide range of polymers soluble from ambient to of 0.25 or 0.15 mg/mL in TCB. Dissolution time was 200ºC can be analyzed in a variety of solvents. 25.00 17.00

90 min 180 min Dissolution time 1 hour with gentle shaking, at 140ºC under nitrogen 20.00 16.50 atmosphere, in order to minimize thermal and oxidative The proposed method takes an automated approach, degradation. Results are presented in Table 1, together and performs all the needed steps without user 15.00 16.00 with standard deviation, when using the IR detector intervention nor solvent handling throughout the 10.00 15.50 for quantifying the injected mass, and when using whole process, paying special attention to the sample y= 1.200x

IV observed at low flow rate R2= 0.998 5.00 the nominal weight given by the analytical balance, condition, minimizing the degradation, as well as Observed IV (dL/g) 15.00 in the IV calculation. An improvement in the precision to laboratory health and safety considerations. 0.00 14.50 0.00 5.00 10.00 15.00 20.00 25.00 is clearly seen when the actual mass measured by the Appropriate dissolution time control and purging of the

IV observed at high flow rate IR detector is considered, given it eliminates any errors vial atmosphere with nitrogen both help in enhanced Fig. 3. Observed intrinsic viscosity for a series or polyethylene 14.00 No purge Nitrogen purge associated with handling small amounts of polymer by reliability of the data, by reducing degradation materials, in tri-chlorobenzene at 150ºC, using high and low Dissolution vial atmosphere flow rate through the two-capillary viscometer. the operator, but also due to the possible presence of possibilities. The application of a fixed forced flow rate Fig. 4. Observed viscosity for an UHMWPE sample with non-soluble particles. for the IV determination maybe also help in improving Application example: Intrinsic Viscosity of different dissolution time, with and without nitrogen purge of the dissolution vial. consistency of data by keeping constant shear in all UHMWPE determinations, while increased flow rate provides Maybe one of the most challenging polymers for An infrared (IR) detector can be optionally used for Sample IV (dL/g) std (IR) std (balance) a net gain in efficiency while maintaining good analysis is ultra-high molar mass polyethylene online accurate quantification of the injected mass, A 11.38 0.2 0.7 correlation of the method with lower shear values. (UHMWPE). Those are high crystallinity materials with which otherwise needs to be entered as weighed B 21.00 0.4 2.6 extremely high values of IV, only soluble at elevated using an analytical balance. The IR detector is C 28.67 0.7 3.8 When applicable, the online IR detection helps in temperatures in organic solvents. Special care must be suitable for detection of polymers with aliphatic CH Table 1. Intrinsic viscosity (IV) for three industrial UHMWPE improving the accuracy and precision of the method, taken in sample preparation to prevent degradation, groups, dissolved and analyzed in solvents that are IR samples analyzed by IVA in TCB at 140ºC. Standard deviation through the direct quantification of the true amount which would reduce the apparent viscosity, and also transparent, such as the important class of polyolefins based on 6 replicates when using the measured injected mass by IR, or using the nominal mass given by the analytical balance. of sample injected. in the analysis, given the high viscosity of the [ηsp] (polyethylene, polypropylene and copolymers), in TCB solutions. or o-DCB.

Quality Control for Polyolefins 49

Upcoming Launch

Chemical Composition Distribution for Quality Control

CEF QC

The latest development in Polymer Char’s Quality Control portfolio, a Crystallization Elution Fractionation instrument for Process Control in production plants. This instrument delivers the chemcial composition distribution for one sample in less than 1 hour (including dissolution). The density results are also provided to facilitate a direct correlation with the traditional process control data in the plant. The instrument can be operated as a CEF, TREF or TGIC.

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