14 Rubber & News • May 3, 2021 www.rubbernews.com www.rubbernews.com Technical Technical

ed and finely dispersed in the matrix. From low-cis to high-cis, to high vinyl Such an experiment is specifi- cally carried out to reveal Intene C30’s high inclination to the com- architecture: an insight into polybutadiene rubber pounding phase, even in severe mixing conditions (short mixing By Federico S. Grasso, Fabio times in combination with high Bacchelli and Salvatore Executive summary filler loading). Such inclination Coppola arises from Intene C30’s peculiar Versalis S.p.A. (Eni) rubber (BR) is commercially available in two main forms. One contains 1,4-cis repeating unit The authors combination of linear and star- Polybutadiene rubber (BR) is levels at around 40 percent, which is called low-cis BR. And the other with levels that range from 92-98 per- Fabio Bacchelli received his branched molecular architecture. the second largest synthetic rub- cent, called high-cis BR. doctorate in chemical engi- In Table 2 we show the results ber produced, next to SBR. Cur- Moreover, high-vinyl polybutadienes may be obtained, which contain pendent vinyl groups as a result of neering from the University of of the lab experiment where, for rently, are the primary appli- 1,2- mechanisms. These rubbers had properties similar to those of SBR and are used with a Bologna, Italy. He began work- the same compound recipe as cation for BR, while other segments specific compounding strategy. ing as a pro- above, we increase the mixing include plastics modification, This paper reports an overview of several different polybutadienes with different molecular architecture cess engineer time in steps from 1.5 minutes to footwear, technical goods and and related property-structure relationships. Functionalization, being a chemical parameter, is not taken at Versalis six minutes. The experiment golf balls. into account. In addition, besides traditional BR grades, new Nd-based polybutadienes containing a specially S.p.A., where confirms that high-cis Neocis designed molecular architecture are introduced, to optimize processing and performance at the same time. he also has BR40 requires longer mixing The molecular architecture able to conjugate those extremely different aspects is discussed on the basis of been leading TECHNICAL NOTEBOOK times than low-cis Intene C30. In the linear viscoelastic response. By considering various recipes, advantages in extrusion behavior and hys- the research Edited by John Dick fact, with optimal mixing condi- teresis are addressed together with commonly used testing parameters. and develop- tions, the compound based on Butadiene may be present in ment depart- Neocis BR40 can achieve very polymer macromolecules in the ment for the competitive performances, even form of cis-1,4, trans-1,4 and 1,2 E l a s t o me r Bacchelli ity and resilience, low heat build- and BR–Co systems make poly- mechanical properties of rubber being superior to Intene C30 in structural units with pendant vi- Physics and Pro- up, high resistance to abrasion mer processing easier in relation compounds were measured ac- terms of mechanical properties nyl groups. The content of individ- cessing unit. and to cut growth, good flexibility to the more linear ob- cording to ASTM, DIN or ISO and reduced energy dissipation ual forms of butadiene structural Bacchelli is head of technical in low temperatures, and high fa- tained by neodymium catalyst. standards. The Rolling Resistance (heat build-up is shown). The units in polymeric chains depends management of SBR/BR/Latex tigue cracking resistance. This But these same characteristics, Index on vulcanized specimens better extrudability of Intene on the polymerization method, in the Elastomer Business set of properties makes high-cis which facilitated processing, influ- was determined through strain C30 remains confirmed, as and it determines the basic prop- Unit. He also is a member of BR an excellent elastomer for the ence in a negative way the mechan- sweep measurements using a tor- shown by the Garvey test. erties of BR, which is commercial- the Scientific Council of the industry. ical properties of the compositions sional bar (5-percent strain, 10 Hz, In Fig. 2 (left) we further ex- ly available in two main forms. German Institute of Rubber On the other hand, its composi- prepared from such polymers. The 60°C). Temperature sweep tests tend the comparison between One containing 1,4-cis repeating Technology. tions do have low skidding resis- physical and rheological properties on vulcanized specimens were low-cis and high-cis BR to all the unit levels around 40 percent is Federico Grasso got his mas- tance and low resistance to heat are dictated by controlling the carried out with torsional bar ge- investigated low-cis grades. The called low-cis BR, and one with ter’s in mechanical engineer- and ozone and, in particular, it is polymer structure. Highly linear ometry at 1 Hz and 2°C/min. polymeric blend ratio is kept levels that range from 91 to 98 ing from the considered a rather difficult poly- neodymium-polybutadiene with a similar to the above-mentioned percent is called high-cis BR. University of mer to process. Four different narrow molecular weight distribu- Results and discussion experiments, but filler type and The demand for these two prod- Catania, Italy. technologies with Ziegler–Natta tion is desirable for high abrasion Low-cis BR loading level are different, as the ucts, each with their own distinct He has been catalysts can be used in the com- resistance, low heat build-up and In Table 1, several Versalis high abrasion resistance recipe properties, comes from major working in mercial production of BR with high tensile properties. Although commercial BR grades are listed. was adopted to further stress on consumption segments such as the Elastomer high 1,4-cis repeating unit levels: linear and ultra-high cis polybuta- Intene materials are obtained by the differences between material tires and retreading, with high- Physics De- (Ti), cobalt (Co), nickel possesses high compound a continuous polymerization pro- grades. Also in Fig. 2 (left), the cis-BR being the most appropriate partment of (Ni), and neodymium (Nd). The viscosity, the disadvantage can be cess, using catalyst, compound before the addition of for these applications. Vulcanized Versalis R&D higher polydispersity and branch- reduced by introducing a branched whereas Neocis BR40 is polym- the curing agent is referred to as high-cis BR presents high elastic- 1,2 and is techni- ing content found in the BR–Ni structure. erized by a continuous solution masterbatch compound. We ob- cal manager Grasso process using a Neodymium cat- serve that masterbatch Mooney Table 1: Properties of Versalis commercial polybutadienes: Europrene se- for tire applications in the Elas- Experimental alyst. The Intene series rep- viscosity depends on the Mooney ries (Neocis and BR HV80) and Intene series. Mooney and Tg data refer tomer Business Unit. Polybutadiene samples used in resents low-cis materials, all viscosity of the raw polymer, with to measured values. Salvatore Coppola got his this work are Europrene and In- having cis content of about 38 the exception of Intene C30 and doctorate in chemical engineer- tene commercial grades from percent and vinyl content of Neocis BR40, which are bottom ing from the Versalis. The main properties about 10 percent, and varying low and top high values in the University of are summarized in Table 1. The Mooney viscosity. masterbatch Mooney raking, re- Napoli Fed- linear viscoelastic behavior of All low-cis polymers have a spectively. erico II in Ita- the raw polymers is obtained prominent linear molecular archi- This result meets our expecta- ly. He joined through frequency sweep test in tecture and narrow molecular tions and is not further com- Versalis R&D SAOS test conditions and tor- weight distribution, with the ex- mented as already discussed as a scientist sional mode (the reference tem- ception of Intene C30, which is a above. This experimental lab and currently perature is 110°C). mixture of linear and star- trial confirms the superior me- is head of the During the test, strain is con- branched polymer chains. Neocis chanical performances of high- Department trolled in order to respect the BR 40 is a traditional Nd-BR cis BR (Neocis BR40) with re- of Elastomer Coppola linear viscoelastic regime of the grade, which we introduce here for spect to the low-cis BR (Intene) Fig. 1: Compound aspect at mixer discharge. Mixing duration is 1.5 min- material. Frequency sweep data comparison with low-cis BR. As Physics. utes. Low-cis BR (Intene C30, left) and high-cis BR (Neocis BR40, right) series. are extended at very low fre- well known in the industrial prac- In Fig. 2 (right), for readability are the investigated materials. The adopted compound formulation is a quency by applying creep/recov- tice, low-cis BR is widely used in gential mixer (1.5 liters). We ob- chafer compound (BR/NR 70/30, 70 phr of N375). purpose we only show the results ery test in the SAOS regime. rubber applications due to its pecu- serve that the compound aspect of abrasion resistance, which is Creep/recovery data are convert- liarity of providing excellent com- is noticeably different if we use the most important parameter, ed into dynamic moduli by means poundability and processability. Intene C30 (left) or Neocis BR40 3 as this formulation is meant for of the Schwarzl relationships. In Fig. 1 we show compounds (right). More precisely, the Neocis high abrasion resistance applica- Compounding was carried out at discharge after a 1.5 minute BR40-based compound still ap- tions. It is interesting to observe using laboratory internal mixers mixing duration step that we pears unfinished, as the carbon that the abrasion resistance in- with Banbury rotors. Physical and carried out in a laboratory tan- black is not properly incorporat- dex shows linear trend with re- Fig. 2: Comparative tests of low-cis BR grades (Intene) vs. high-cis BR (Neocis BR40) in high abrasion resistance spect to the average molecular formulation. Polymer ratio is BR/NR=75/25; filler loading is 75 phr of N234. Mixing is performed in two stages in a weight of the raw polymer. We Table 2: Comparative laboratory test for chafer compound (BR/NR laboratory Banbury mixer; the overall mixing time is six minutes. Masterbatch Mooney vs. raw polymer Mooney is selected Intene 50 and Intene 70/30, 70 phr of carbon black N375). A) Low-cis BR (Intene C30), B) shown on the left. The abrasion resistance index is shown as a function of the polymer’s average molecular weight C30 with comparable Mooney High-cis-BR (Neocis BR40). on the right. This index is calculated assuming Neocis BR40 as reference (value is 100) so that higher value means viscosities; we observe differenc- better performance. The molecular weight of low-cis grades is normalized to the molecular weight of Neocis BR40. es in the compound properties, due to their different molecular architectures (partially star- branched vs. fully linear struc- ture). In Fig. 3 we show the dynam- ic-mechanical loss tangent curves as a function of tempera- ture. All plots show two distinct peaks, one of which always oc- curs at around -55°C, while the other can be located at either -75°C or -90°C, depending on the BR type. The presence of two peaks in the compound indicates the immiscibility between the

P014_P016_RPN_20210503.indd 14 4/28/21 2:07 PM www.rubbernews.com www.rubbernews.com Rubber & Plastics News • May 3, 2021 15 Technical

ed and finely dispersed in the NR and the BR phases, with the so the Neocis BR40 phase peak ice skid resistance, wet grip and branching content typical of Ni- polymer matrix. local maxima being ruled by the would be reasonably expected to rolling resistance indexes at the BR and Co-BR make polymer Such an experiment is specifi- transition glass temperature be higher unless crystallization same time. processing easier in relation to cally carried out to reveal Intene values of the raw materials. is taken into account. the more linear architecture ob- C30’s high inclination to the com- Focusing on the local maxima High-cis BR tained by neodymium catalyst. pounding phase, even in severe of loss tangent curves, com- High-vinyl BR Four different technologies with On the other hand, these same mixing conditions (short mixing pounds show peaks with differ- After discussing low-cis BR Ziegler–Natta catalysts can be characteristics, which facilitated times in combination with high ent heights, thus suggesting dif- polymers in comparison with used in the commercial production processing, influence in a nega- filler loading). Such inclination ferent filler distribution10 and high-cis BR, we provide an in- of BR with high 1,4-cis repeating tive way the vulcanizate proper- The authors arises from Intene C30’s peculiar filler dispersion11 within the sight into the BR HV80 Versalis unit levels: titanium (Ti), cobalt ties of the compositions prepared combination of linear and star- NR/BR phases. To further ex- commercial grade. The latter is a (Co), nickel (Ni), and neodymium from such polymers. Fabio Bacchelli received his branched molecular architecture. plore this point, in Fig. 4 we show solution polymerized high vinyl (Nd). Depending on the type of Table 4 summarizes literature doctorate in chemical engi- In Table 2 we show the results the values of the loss tangent butadiene polymer produced by catalyst, different molecular ar- data,1 providing a qualitative in- neering from the University of of the lab experiment where, for peak related to the BR phase as a continuous process using a lithi- chitectures are achieved, with dif- sight into major advantages/disad- Bologna, Italy. He began work- the same compound recipe as function of the normalized mo- um catalyst.4,5 ferent molecular weight distribu- vantages of different high-cis BR ing as a pro- above, we increase the mixing lecular weight of the raw poly- BR HV80 has a vinyl content of tions as well as different branching types in two different carbon black- cess engineer time in steps from 1.5 minutes to mers. We observe a good correla- around 77 percent, comparable levels. In Fig. 6, a qualitative based compound formulations. Nd- at Versalis six minutes. The experiment tion for the Intene grades, while to that of high vinyl SSBR. schematic of branching levels vs. BR clearly provides excellent me- S.p.A., where confirms that high-cis Neocis instead the high-cis BR grade High-vinyl BR can be used in catalyst type is shown. chanical properties as well as low he also has BR40 requires longer mixing (Neocis BR40) does not fit the compound applications requiring High-cis Nd-BR is known to be levels of hysteresis for the cured been leading times than low-cis Intene C30. In trend. This result is somehow specific performances at low a high performing, very elastic compounds, due to molecular pat- the research fact, with optimal mixing condi- expected, as it is known from the temperature. As an example, we polymer. However, processing terns featuring higher linearity. and develop- tions, the compound based on literature12 that high-cis BR can refer to SSBR/BR/NR compounds may become challenging, as seen To further investigate differ- ment depart- Neocis BR40 can achieve very experience crystallization at tem- for winter tread with polymer for example in rough extrudates. ences, we have considered and ment for the competitive performances, even peratures near or below 0°C, and ratios of 55/40/20 respectively. The higher polydispersity and E l a s t o me r Bacchelli See Polybutadiene, page 16 being superior to Intene C30 in that the crystallization strongly SSBR is a continuous high-vi- Physics and Elastomer Pro- terms of mechanical properties affects the viscoelastic response nyl SSBR (SOL R C2564T, TDAE Fig. 5: Dynamic-mechanical curves of SSBR/BR/NR compounds for cessing unit. and reduced energy dissipation of the raw material, in terms of extended, 25 percent winter tread and polymer ratio of 55/40/20, respectively. SSBR is a Bacchelli is head of technical (heat build-up is shown). The loss tangent and moduli.13 (w/w) over total chain units and TDAE oil-extended grade polymerized in continuous process and having management of SBR/BR/Latex better extrudability of Intene As a consequence, the value of vinyl 64 percent (w/w) over buta- styrene/vinyl composition of 25/64 percent in weight. The adopted BR in the Elastomer Business C30 remains confirmed, as the Neocis BR40-phase peak in diene chain units. type is Neocis BR40, while filler is precipitated silica in a content of 95 Unit. He also is a member of shown by the Garvey test. Figs. 3 and 4 cannot be directly The adopted BR type is Neocis phr. High vinyl BR (BR HV80) is introduced in partial replacement of the the Scientific Council of the In Fig. 2 (left) we further ex- compared with the values of In- BR40, while filler is precipitated SSBR, in maximum amount of 20 phr. In the plot, the loss tangent curves German Institute of Rubber tend the comparison between tene grades. An additional indi- silica in a content of 95 phr. BR of cured compounds with and without BR HV80 are shown. Technology. low-cis and high-cis BR to all the cation of this crystallization ef- HV80, introduced in partial re- Federico Grasso got his mas- investigated low-cis grades. The fect occurring in Neocis BR40 placement of the SSBR (20 phr), ter’s in mechanical engineer- polymeric blend ratio is kept can be found again in Fig. 3, is able to improve the loss tan- ing from the similar to the above-mentioned where the local maximum of the gent curve in the range from University of experiments, but filler type and NR phase is located at lower po- -30°C to +20°C (Fig. 5). Data in Catania, Italy. loading level are different, as the sition for the Neocis BR40-based- Table 3 shows that lower values He has been high abrasion resistance recipe compound curve. This suggests of the complex dynamic modulus working in was adopted to further stress on that higher filler incorporation (G*) are found in the same tem- the Elastomer the differences between material occurs in the NR phase when perature range. High-vinyl BR, Physics De- grades. Also in Fig. 2 (left), the Neocis BR40 is used in the com- when properly formulated, partment of compound before the addition of pound in place of Intene grades, brings about improvement in the Versalis R&D the curing agent is referred to as and is techni- masterbatch compound. We ob- Fig. 3: Dynamic-mechanical curves of BR/NR cured compounds are cal manager Grasso serve that masterbatch Mooney shown. Details about mixing conditions and compound recipe are avail- for tire applications in the Elas- viscosity depends on the Mooney able in Fig. 2. Measurements are carried out in torsion at low deformation tomer Business Unit. viscosity of the raw polymer, with level (strain=0.1%) and 1Hz frequency. Salvatore Coppola got his the exception of Intene C30 and doctorate in chemical engineer- Neocis BR40, which are bottom ing from the low and top high values in the University of masterbatch Mooney raking, re- Napoli Fed- spectively. Table 3: Tire predictors for winter tread SBR/BR/NR silica compound. erico II in Ita- This result meets our expecta- The introduction of high-vinyl BR (BR HV80) in partial replacement of ly. He joined tions and is not further com- SSBR brings about improvement of the major dynamic properties. Values Versalis R&D mented as already discussed are indexed so that higher values mean better performance. as a scientist above. This experimental lab and currently trial confirms the superior me- is head of the chanical performances of high- Department cis BR (Neocis BR40) with re- of Elastomer Coppola spect to the low-cis BR (Intene) Physics. series. In Fig. 2 (right), for readability gential mixer (1.5 liters). We ob- purpose we only show the results Fig. 6: Schematic chart of high-cis BR grades using different catalytic serve that the compound aspect of abrasion resistance, which is systems. Comparison is limited to the catalysts typical of industrial po- is noticeably different if we use the most important parameter, lymerization processes. Intene C30 (left) or Neocis BR40 as this formulation is meant for (right). More precisely, the Neocis high abrasion resistance applica- BR40-based compound still ap- Fig. 4: The values of the loss tangent are taken at the local maxima (y-ax- tions. It is interesting to observe is), which is related to the BR-phase (peaks occurring in the curves at pears unfinished, as the carbon that the abrasion resistance in- black is not properly incorporat- lower temperature values, see Fig. 3). The normalized molecular weight dex shows linear trend with re- (x-axis) is calculated by normalizing the molecular weight of low-cis BR Fig. 2: Comparative tests of low-cis BR grades (Intene) vs. high-cis BR (Neocis BR40) in high abrasion resistance spect to the average molecular (Intene grades) to the molecular weight of high-cis BR (Neocis BR40). formulation. Polymer ratio is BR/NR=75/25; filler loading is 75 phr of N234. Mixing is performed in two stages in a weight of the raw polymer. We laboratory Banbury mixer; the overall mixing time is six minutes. Masterbatch Mooney vs. raw polymer Mooney is selected Intene 50 and Intene shown on the left. The abrasion resistance index is shown as a function of the polymer’s average molecular weight C30 with comparable Mooney on the right. This index is calculated assuming Neocis BR40 as reference (value is 100) so that higher value means viscosities; we observe differenc- better performance. The molecular weight of low-cis grades is normalized to the molecular weight of Neocis BR40. es in the compound properties, due to their different molecular architectures (partially star- Table 4: Different high-cis-BR types are tested in carbon black-based branched vs. fully linear struc- compound recipes. Comparative data are shown in terms of qualitative ture). ranking, by using digits from 1 to 3, being the best and the worst perfor- In Fig. 3 we show the dynam- mances, respectively. Such typical data, that we have re-elaborated, are ic-mechanical loss tangent taken from the literature.1 curves as a function of tempera- ture. All plots show two distinct peaks, one of which always oc- curs at around -55°C, while the other can be located at either -75°C or -90°C, depending on the BR type. The presence of two peaks in the compound indicates the immiscibility between the

P014_P016_RPN_20210503.indd 15 4/28/21 2:11 PM 16 Rubber & Plastics News • May 3, 2021 www.rubbernews.com Technical

and end properties, since these picture, the phase angle, calcu- material showing lower elasticity Neocis BR40 as reference mate- two issues set conflicting require- lated from the loss tangent value in the explored frequency spec- rial and we run a comparative Polybutadiene ments for the rubber. Slower ex- at each measuring frequency, is trum. This difference of the extrudability test with Neocis trusion speeds, lower processing represented as a function of a phase angle value can be related BR45EP by means of a laborato- Continued from page 15 temperatures and addition of normalized rheological parame- with the different elasticity.14 ry extruder equipped with a re-elaborated compound data processing aids are typically re- ter, namely the ratio of the com- Due to the known exponential Garvey die. Although the pic- about Ni-BR and Nd-BR, which quired to improve processability plex modulus |G*| and the rub- dependence of rheological proper- tures in Fig. 9 do not represent 2 0 we retrieved from the literature. of Nd-BR, but these measures bery plateau modulus G N. ties on branch length, the latter the extrudates in the same scale, Two Nd-BR pilot plant products cause higher costs. The phase angle is lower for needs to be carefully designed to it is relevant to note the differ- having different branching levels This conflict between superior materials with enhanced elastic get the desired balance between ence in the surface quality (flat are compared with Ni-BR. The properties of Nd-BR and chal- properties and, for materials processing and mechanical proper- surface and sharp corners) that results of data elaboration are lenging processing may be over- with similar polydispersity in- ties. It should be remembered, in the extrudates of the two differ- shown in Fig. 7 . The plot clearly come by using specially designed dex, the Van Gurp-Palmen plot fact, that processability can even ent compounds achieve. shows that the lower the branch- grades. A summary of various can account for the contribution become very bad if branching con- The extrudability of the un- ing content the better results are performance aspects as a function of the branched patterns to the tent and chain length both increase cured compound is positively im- found for rebound (higher), abra- of molecular design of Nd-BR is elastic response of the material. up to exceedingly high values.15 In- pacted by the replacement of sion resistance (lower amount of briefly reported in Table 5 . Be- In Fig. 8 we observe that Neocis stead, when comparing the Neocis Neocis BR40 with Neocis abraded material) and heat build- sides typical compound proper- BR45EP has a dynamic response, BR45EP curve with the one of ref- BR45EP, while mechanical prop- up (lower hysteresis). On the con- ties, it is important to remember which lays in between the as- erence linear Nd-BR, there is just erties of BR45EP are comparable trary, when approaching struc- that highly branched materials sumed reference structures, that an intermediate region of the Van to those of BR40. Moreover, to tures with higher branching, the show reduced shelf life in terms of is the linear and the highly Gurp-Palmen plot, where BR45EP better point out the optimum uncured compounds achieve low- Mooney stability of the raw poly- branched Nd-BR materials shows a higher elastic response. compromise between process- er Mooney viscosity. mer during storage (Mooney rise (which are both model polymers). In Fig. 9 , we show the different ability and hysteretic properties, phenomena), due to internal mo- More precisely, with respect to extrusion behavior of uncured Neocis BR45EP was tested in an High-cis Nd-BR with optimized lecular rearrangements.7 the highly branched Nd-BR, tire compound for high abrasion SSBR/BR silica tread compound, structure The new Versalis Nd-BR grades Neocis BR45EP has much higher resistance, which is rich in BR where BR is the minor polymeric As discussed above, due to lim- featuring optimized structure values of the phase angle, sug- content (75 percent). To assess component. The Rolling Resis- ited processability of Nd-BR can be the best solution for cus- gesting that the molecular struc- the advantages of Neocis tance Index is improved by 10 during the transformation process tomers requiring enhanced pro- ture of Neocis BR45EP is signifi- BR45EP over a standard com- percent vs. the compound con- typical of rubber compounding, cessability of uncured compounds cantly different, with the mercial BR type, we assume taining Neocis BR40. polymer producers have lately un- on top of excellent properties of To further prove the beneficial dergone several industrial practic- the vulcanized rubber. Fig. 8: Reduced Van Gurp-Palmen plot of the specially designed Neocis effect of the optimized structure, es to increase the branching level We introduce linear viscoelas- BR45EP vs. Nd-BR linear reference and Nd-BR highly branched reference. we finally consider Neocis BR61EP of Nd-BR. So several structures tic measurements to give an in- The reference samples (Nd-BR linear and Nd-BR highly branched) are in comparison with Versalis Nd- are industrially possible for Nd- sight into the structures of the model polymers. BR standard grades, Neocis BR, which nowadays can range different Nd-BR under investiga- BR60 and Neocis BR40. All those from mainly linear to highly tion. In Fig. 8, frequency sweep materials were tested in sidewall branched architectures (Fig. 6 ). data of the raw polymers are ar- NR/BR compounds and the re- While high levels of branching ranged to represent a reduced sults of Garvey extrusion are can be achieved by applying Van Gurp-Palmen plot. This plot shown in Fig. 10 . post-modification processes, that representation is widely adopted The compound extrudate is not the case of the optimized in the literature8,9 as a valuable based on Neocis BR61EP is found structures, which are the new Nd- way to identify differences in to clearly show enhanced quality BR grades proposed and commer- terms of molecular architecture surface than the compound cialized by Versalis. between different polymers. This based on Neocis BR60. Further- In particular, a high degree of way of plotting dynamic-mechan- more, despite the Mooney viscos- branching is not beneficial to ical data provides the advantage ity difference between Neocis hysteretic properties, as already of being independent of test tem- BR61EP and Neocis BR40, the reported for SSBR.6 Optimal perature, relaxation time, chemi- optimized structure of Neocis compound properties are, then, a cal composition and average mo- BR61EP allows achieving com- compromise between processing lecular weight. In the reported petitive, and in this specific case, even superior Garvey results. Fig. 7: Plot of cured compound properties as a function of the normalized compound Mooney for different high-cis BR types (nickel vs. neodymium Acknowledgments BR). Polymers have different molecular architectures (branched patterns). The authors are indebted to We used different colors for each material type. Symbols having larger Versalis for the permission to Fig. 9: Samples of uncured compounds extruded through the Garvey die sizes account for increasing branching content of the raw polymer; the publish this work, and to Piera of a laboratory extruder. The adopted compound formulation is for tire branching content is proportional to the ratio: (Mooney/Solution Viscosi- De Marco, Giovanni Cuder, An- chafer. Polymers involved are BR/NR in ratio 75/25; filler type is N234 in ty). The values in the x-axis are calculated as: Compound Mooney/Refer- drea Nocerino and Luigi Franchi- amount of 75 phr. The Garvey extrusion test was carried out at 100 rpm ence Compound Mooney. Rebound, abrasion resistance and HBU (y-axis) ni for the experimental support. and 90°C on uncured compounds after five days aging at room tempera- were indexed with respect to the reference compound, so that higher val- Maria Elisa Pattuelli, Giuliano ture. In the picture, the extrudates of the compounds with Neocis BR40 ues mean better performance. We assumed the Ni-BR-based compound Fiscaletti and Antonio Solito are as reference. Dashed lines are sketched for each compound property to (above) and Neocis BR45EP (below) are compared. 2 gratefully acknowledged for poly- improve data readability. We elaborated data taken from the literature. mer chemistry and design.

References 1. N. Pires et al., J. Appl. Polym. Sci. 99, 88 (2006). 2. G. Kwag et al., Polymer 46, 3,782 (2005). 3. F.R. Schwarzl, Rheol. Acta 8, 6 (1969). 4. L. Gargani, P. De Ponti, M. Bruzzone, Kautsch Gummi Kunstst. 10, 935 (1987). 5. A. Yoshioka, K. Komuro, A. Ueda, H. Watanabe, S. Akita, T. Masuda, A. Nakaji- ma, Pure and Appl. Chem. 58, 1,697 (1986). 6. F. Grasso, F. Bacchelli, S. Coppola, B. Pellizzari, Kautsch. Gummi Kunstst., 10, 45 (2019). 7. S. Coppola, F. Bacchelli, G. Marrucci, G. Fig. 10: Samples of uncured compounds extruded through the Garvey die Ianniruberto, J. Rheol., 58, ,1877 (2014). of a laboratory extruder. The adopted compound formulation is for tire side- 8. S. Trinkle, P. Walter, C. Friedrich, Rhe- wall. Polymers involved are BR/NR in ratio 50/50; filler type is N375 in ol. Acta, 41, 103 (2002). 9. S. Trinkle, C. Friedrich, Rheol. Acta, amount of 45 phr. Mooney 60 polymers (Neocis BR60 and Neocis BR61EP) 40, 322 (2001). are compared with Mooney 40 material (Neocis BR40). The Garvey extru- 10. N. Warasitthinon, C.G. Robertson, sion test was carried out at 20 rpm and 90°C on uncured compounds. Rubber Chem. Technol., 91, 577 (2018). 11. C.G. Robertson, C.J. Lin, M. Rackai- tis, C.M. Roland, Rubber Chem. Technol., 41, 2,727 (2008). Table 5: Performance overview of different high-cis Nd-BR with different mo- 12. A. De Chirico, P.C. Lanzani, E. Raggi, lecular architecture. The traditional reference BR has a mainly linear structure. M. Bruzzone, Die Makromolekulare Che- mie, 175, 2,029 (1974). 13. N.V. Pogodina, H.H. Winter, Macro- molecules, 31, 8,164 (1998). 14. E. van Ruymbeke, S. Coppola, L. Ba- lacca, S. Righi, D. Vlassopoulos, J. Rheol., 54(3), 507-538 (2010). 15. S. Bhattacharjee, H. Bender, and D. Padliya, Rubber Chem. Technol., 76(5), 1,057-1,073 (2003).

P014_P016_RPN_20210503.indd 16 4/28/21 2:14 PM