(PLA)/Polycaprolactone (PCL) Composite Microfibre Membranes

Home , Polycaprolactone

Yao Lu, Yan-Chun Chen, Preparation and Characterisation *Pei-Hua Zhang of Polylactic Acid (PLA)/Polycaprolactone Key Laboratory of Textile Science and Technology, Ministry of Education, (PCL) Composite Microfibre Membranes Donghua University, Shanghai 201620, China, *E-mail: [email protected] DOI: 10.5604/12303666.1196607

Abstract Biodegradable polymers like PLA and PCL have wide application in tissue engineering because of their biocompatibility, degradation and mechanical properties. In this study, the optimised electrospinning parameters of PLA/PCL composite membranes were determined with scanning electron microscopy to obtain smooth and relatively fine microfibre. The properties and structure of electrospinning PLA, PCL and PLA/PCL(70/30) membranes were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), the water contact angle, water absorption degree and tensile strength. The results revealed that PLA/PCL composite membranes possessed better mechanical and hydrophilic properties when compared to single component microfibre membranes like PLA and PCL. The improvements above are conducive to microfibre membrane application in the biomedical sector.

Key words: PLA/PCL, electrospinning, microfibre membrane, property.

The earliest origin of electrospinning mers for biomedical application. Poten- is the electrostatic spray phenomenon tial applications include drug-loading, found by Rayleigh in the late 19th cen- intravascular stent and medical implant tury [9], and later Formales started to mesh. PLA/PCL composite membranes n Introduction study electrospinning technology. Sev- were prepared and compared to PLA and Polylactic acid (PLA) and polycaprol- eral researches have demonstrated elec- PCL samples to demonstrate the superi- actone (PCL) are biomedical materials tropinning is an effective method which ority of multi-component electrospinnng approved by the USA Food and Drug can prepare superfine fibres with - diam membranes. The reduction of the crystal- Administration (FDA) for their non- eters from 5nm to 1μm that possess high linity degree can significantly accelerate toxic and good biological compatibility. a specific surface area and porosity [10 the degradation rate, and the increase in They are often used in tissue engineer- - 12] using different materials like PLA, the tensile strength and elongation can ing or imitating extracellular matrix as PEO & PLGA. These features enable improve the supporting capacity. This functional materials for cell growth [1, electropinning to have wide application paper discusses the electrospinning pro- 2]. PCL has excellent biological com- in biological engineering. Kwon et al. cess parameters of PLA/PCL composite patibility and toughness mainly applied [13] found that umbilical cord vascular membranes. Scanning electron micros- in a controlled releasing carrier, such as endothelial cells had good prolifera- copy (SEM), differential scanning calo- drug loading, etc. However, PCL needs tion and adhesion on finer fibre (0.3 and rimetry (DSC), X-ray diffraction (XRD), 2 - 4 years to degrade completely [3]. 1.2 μm). Boland [14] prepared PLA/PCL the water contact angle, water absorption PLA is the most used biodegradable electrospinning membranes with differ- and tensile strength techniques were used material by far because it has good bio- ent diameters and morphology to expand to investigate the structure, morphology logical compatibility and significantly its application in biological engineering. and properties of electrospun PLA, PCL high strength and modulus. PLA’s final Yang et al.[15] found that smooth muscle and PLA/PCL microfibres. products of degradation are CO2 and cells grew better on a PLA/PCL blend H2O, and the intermediate products are stent than on a single component of PLA lactic acid and hydroxy acid, which are stent. Papers studying PLA/PCL electro- n Experimental all accepted by the body [4]. Although spinning fibres can be classified into two Materials PLA’s strength is high, there still exist categories: the preparation technology of problems such as low elongation, poor PLA/PCL and application of PLA/PCL. Poly(D,L-lactic acid) and PCL polymers toughness and weak impact-resistance Most papers place emphasis only on were purchased from Yisheng New Ma- strength. Aiming at improving the slow one aspect. Our research combined both terials Co., LTD (Shengzhen, China). degradation rate, poor hydrophilicity, technological parameters and properties The molecular weight of PLA is 105 weak strength and cell-attached force of of PLA/PCL electrospinning fibres, and and that of PCL’s - 8×104. Methylene PCL, introducing other biodegradable compared them to PLA and PCL single dichloride (DCM) and N,N-dimethyl components to make up for the poor as- component fibres. However, the methods formamide (DMF) were obtained from pects of PCL performances has encour- we used are more comprehensive. the Damao Chemical reagent factory aged more research into materials such (Tianjing, China). All of the chemicals as PCL/PHBV, PCL/Collegen and PCL/ Electrospinning technology is well suited were analytical reagent grade and were Polyethylene glycol [5 - 8]. to process synthetic biocompatible poly- used with no further purification.

Lu Y, Chen YC, Zhang PH. Preparation and Characterisation of Polylactic Acid (PLA)/Polycaprolactone (PCL) Composite Microfibre Membranes. 17 FIBRES & TEXTILES in Eastern Europe 2016; 24, 3(117): 17-25. DOI: 10.5604/12303666.1196607 Preparation of the spinning solution target). The degree of crystallinity was Solvent ratio (DCM:DMF) and electrospinning process determined by implementing the area DCM and DMF were chosen as solvents PLA and PCL polymers were dissolved integration method from XRD intensity for producing PLA/PCL electrospin- at different ratios with DCM and DMF data over the range of 2θ from 0° to 60°. ning fibres. The ratio of DCM:DMF mixed solvents. The solution was stirred The calculation of the degree of crystal- is one of the most controlling param- until completely dissolved using a mag- linity was according to Equation 1. eters of the morphologies. Five ratios of netic blender. For the electrospinning DCM:DMF ranging from 100:0, 80:20, process, the solution was sucked into (1) 70:30 & 60:40 were studied in this stage. a 5 ml-syringe pump. The syringe was Figure 1 shows SEM photos of electro- then put on an iron support. The receiv- where, Ic is the intensity of the crystal- spinning PLA/PCL fibres at different sol- ing device was aluminum foil connected lisation peak, and Ia is the intensity of vent ratios of DCM/DMF. PLA/PCL so- to the ground. The solution was stretched the amorphous peak. lutions were prepared at a concentration under the action of the electrostatic field of 8%. The positive voltage applied was force upon the opening of high voltage, Hydrophilic evaluation 14 kV, the receiving distance - 15 cm, eventually forming disorderly microfi- The hydrophilic contact angle is an im- the flow rate of the polymer solution - bre membranes along with the evapora- portant indicator characterising the mate- 0.6 ml/h, and the PLA/PCL blending tion of the solvent. The machine adopted rial’s hydrophilic performance, measured ratio was 70/30. Without DMF or little in the research was an 85-2A Magnetic by a OCA15EC Contact Angle Meter DMF, the dominant morphologies (Fig- stirrer (Huanyu Technology Instrument (Beijing North Defei Co,. Ltd., Beijing). ures 1.a & 1.b) are those that have fibres Factory, China), LSP01-1A micro-injec- The experiment was conducted at room with relatively large diameters or fibres tion pump (Longer Precision Pump Co., temperature using a yellow-light source, with uneven diameters. With too much Ltd, China) and JG 50-1 Dc high voltage with a water volume of around 4 μl. Each DMF, there was a serious adhesion phe- transmitter (Shanghai Shenfa Detecting sample was tested in 5 different posi- nomenon (Figures 1.d & 1.e) throughout Instrument Factory, China). tions. The final average contact angle the microfibrous samples. In this case, was calculated from these 5 data. the reason was the incomplete evapora- Characterisation of the structure and tion during the movement of the poly- performance Water absorption mer jet toward the collector. Therefore Water absorption was characterized by the ratio of DCM: DMF of 80:20 maybe Scanning electron microscopy (SEM) the water absorption degree. Samples the most suitable choice for gaining rela- The surface structure of the microfibre were cut into 4 × 4 cm pieces and im- tively fine fibre with smooth morphology. membranes was characterised by a HI- mersed in PBS solution for 24 hours. TACHI S - 3000 scanning electron micro- The degree of water absorption was ac- Solution concentration scope (HITACHI Co,. Ltd., Japan). The cording to Equation 2 The concentration also has an important average fibre diameter was calculated effect on microfibre morphologies. Three using 100 individual diameters for each (2) concentrations of solution ranging from sample with Photoshop CS3 software. R is the water absorption degree, W the 8, 10 & 12% were studied in this stage. The pore diameter of the membranes’ 0 initial weight of samples, and W is the These parameters were chosen based on surface was analyzed by an American 1 weight of immersed samples that were a pre-experiment where we found that contador automatic membrane pore drip-dried by filter paper. the concentration was smaller than 8%, measuring instrument. for example 6% of the liquid drop was re- Mechanical performance ceived instead of microfibres. And when Differential scanning calorimetry (DSC) Membranes were cut into 40 × 5 mm rec- the concentration was bigger than 12%, Thermal analysis of the microfibre mem- tangle samples, and their effective tensile the electrospinning process could not last branes was conducted by DSC. Dry length samples was 20 mm. The uniaxial for a long time, and the needle may oc- samples (5 mg) were heated from 20 to tensile test was carried out at a tensile clude after about 30 minutes. Figure 2 200 °C at a scanning rate of 10 °C/min rate of 10 mm/min. The average tensile presents the fibre-diameter distribution using Phrisl differential scanning calo- strength and elongation was calculated of PLA/PCL microfibres at different so- rimetry (USA) under nitrogen atmos- from 5 samples. The thickness, which lution concentrations. Fibres prepared phere. was controlled at about 0.05 mm, was by electrospinning had a solvent ratio of measured by a micrometer caliper accu- DCM:DMF = 80:20. The positive volt- X-ray diffraction (XRD) rate to 0.01 mm. age applied was 14 kV, the receiving dis- The crystallisation property was obtained tance - 15 cm, the flow rate of the poly- by XRD measurements, which were re- mer solution - 0.6 ml/h, and the PLA/PCL corded using a Shimadzu XRD-6000 dif- n Results and discussion blending ratio was 70/30. For lower con- fractometer (Germany). XRD measure- centrations of solutions in the eletrospin- Electrospinning process parameters ments of the microfibre samples prepared ning process, the average fibre diameter were made at 40 kV and 200 mA. A Cu-Kα The experiment discussed the effect rose with a wider distribution range. radiation source was used to scan the sam- of parameters on the electrospinning ples in a 2θ range from 0° to 60° at a scan membranes’ surface structure, including To enhance the application of microfibre rate of 0.06°/s. The d-spacing was deter- the solvent ratio (DCM: DMF), PLA/PCL in tissue engineering, fibrous membranes mined from Bragg’s law (nλ = 2 d sin θ), blending ratio, solution concentration, should acquire the following parameters where θ is the diffraction angle, and λ is voltage, and receiving distance (distance according to Zeinab Karami et al.[16]: the wave-length (λ = 1.54056 Å for a Cu between the needle tip and target). The absence of beads allows to prevent

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d) e)

Figure 1. Scanning electron micrographs of PLA/PCL microfibres in DCM/DMF at different solvent ratios; a) DCM:DMF = 100:0, b) DCM:DMF = 90:10, c) DCM:DMF = 80:20, d) DCM:DMF = 70:30, e) DCM:DMF = 60:40. trapped portions of the drug and ensure microfibres at a concentration of 8% as the voltage applied. The principle of drug-release. What is more, the minimum (Figure 2.a), with an average diameter the voltage’s action can be understood as average diameter and concentrated fibre of 312.6 nm and concentration distrib- follows [17]: The surface of the polymer distribution result in the surface-area- uted between 200 to 400 nm. solution at the tip of the spinneret be- volume ratio of the microfibres, which is comes charged along with the movement good for cell adhesion, proliferation and, Voltage of ions. When the electric force is high remarkably, the drug molecule tendency. It has been observed that the shape of enough to overcome the surface tension’s On the basis of the requirements above, the initiating droplet can be changed by force, a straight and quasi-stable charged the best sample selected were PLA/PCL several electrospinning parameters, such jet is formed. Therefore a suitable effect

0.30 0.25 a)Average - average Diameter: diameter 584.7nm 584.7 nm b) Average- average Diamter: diameter 312.6 312.6 nm nm 0.25 0.20

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300 400 500 600 700 800 900 1000 1100 Distribution Frequency 0.05 FibreFiber diameter,Diameter nm(nm) 0.00 0.40 c)Average - average Diameter: diameter 923.8nm 923.8 nm 100 150 200 250 300 350 400 450 500 550

0.35 FiberFibre diameter,Diameter nm(nm)

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0.15 Figure 2. Fibre-diameter distribution of PLA/PCL 0.10 microfibres at different solution concentrations; Frequency distribution Frequency Distribution Frequency a) 8% - average diameter 584.7 nm, b) 10% - aver- 0.05 age diameter 312.6 nm, c) 12% - average diameter

0.00 923.8 nm. 200 400 600 800 1000 1200 1400 1600 1800 FiberFibre Diameter diameter, (nm) nm

FIBRES & TEXTILES in Eastern Europe 2016, Vol. 24, 3(117) 19 Table 1. Fibre diameter and deviation of bres collected at different receiving dis- Table 2. Fibre diameter and deviation of PLA/PCL microfibres collected under - dif tances ranging from 15 to 27 cm (when PLA/PCL microfibres collected under - dif ferent voltages. the distance was 27 cm, there were very ferent receiving distances. Voltage, kV Fibre diameter, nm few fibres deposited on the aluminum Receiving distance, cm Fibre diameter, nm 12 384.3±14.8 foil, which made it impossible for us to 15 384.3±18.3 14 312.6±16.1 calculate its average diameter). The other 18 433.5±24.5 16 576.3±27.3 electrospinning parameters were as fol- 21 428.5±21.2 18 528.0±31.6 lows: a ratio of DCM:DMF of 4:1, a solu- 24 419.3±22.9 20 517.4±30.7 tion concentration of 8%, and voltage of 12 kV. Compared with other parameters, homogeneity and calculate their average of the voltage is actually the balance be- the receiving distance had little effect on diameter. Some researches also obtained tween the electric force and surface ten- the fibre diameter, but an increase in dis- the solvents’ voltatility as an evaluation sion, which is critical to determine the in- tance may lead to fewer fibres deposited index by using the Fourier Transform itial cone shape of the polymer solution on the aluminum foil. Figure 3 shows Infrared Spectroscopy (FTIR) technique. at the tip of the spinneret. Moreover SEM photos of microfibres collected at However, the paper did not test the sam- the effective voltage is associated with the same time at two different receiving ples’ FTIR, the reasons for which can be the solution’s features, such as concen- distances. When the distance was in- explained as follows: First the solvents tration. Table 1 shows the fibre’s aver- creased to 27 cm (Figure 3.b), there were we used in the experiment were DCM age diameter and deviation of PLA/PCL very few fibres collected. Therefore the and DMF, in which DCM has good vola- microfibres collected under different receiving distance of 15 cm seemed suit- tility and can be volatilised completely in voltages. The ratio of DCM:DMF was able for PLA/PCL electrospinning. air in a short time, while DMF cannot be 80:20, the solution concentration - 8%, volatilised as its boiling point is 152.8 °C. the receiving distance - 15 cm, the flow PLA/PCL blending ratio Therefore we can state that there must be rate of the polymer solution - 0.6 ml/h, Figure 4 shows SEM photos of PLA/PCL some DMF remaining in the membrane and the PLA/PCL blending ratio was membranes at different blending ratios. even without the FTIR test. However, the 70/30. The initiating jet was formed Figure 5 shows the fibre diameter distri- paper was aimed at comparing PLA/PCL when the voltage exceeded 8 kV, but bution of PLA/PCL = 70/30, as well as to PLA and the PCL single component the jet was not stable at a voltage below PLA and PCL single component mem- electrospinning membrane, which were 12 kV. The jet suspended at the tip of the branes using the same electropinning pa- all prepared under the same conditions spinneret and formed a conical-shaped rameters. From Figure 4, we can see that that will not be affected by DMF re- solution (Taylor Cone). By increasing adding PCL to PLA leads to the uneven- mains. Another important reason is that the voltage, the solution was removed ness of the fibre from the SEM photos. It the parameters we chose in the paper was from the tip more quickly and uniform can be seen that the sample of PLA/PCL a group of relatively suitable parameters fibre formed. When the voltage was in- 90/10 had the most obvious fibre -un instead of the best one for PLA/PCL elec- creased to 18 kV, the Taylor cone shape evenness phenomenon (Figure 4.a). tospinning fibres under the conditions we oscillated and became asymmetrical, re- The PLA/PCL ratio of 70/30 selected mentioned herein. This means that even sulting in a large diameter irregularity of has the best morphology compared to the if another person also prepared PLA/PCL fibres. AsTable 1 shows, both fibre diam- others, and was thought of as the most membranes using the parameters we eters were relatively small at a voltage of suitable ratio. When the PLA and PCL mentioned, he or she may not get sam- 12 kV and 14 KV. But the diameter de- ratio was 70:30, the fibre diameter was ples with the best morphology, because viation was the smallest when the voltage distributed well from 300 to 400 nm even same materials can have different was 12 kV, which means more uniform (Figure 5.b). properties, such as the molecular weight; fibrous morphologies. and the environment condition, including Overall a group of suitable process- temperature or humidity, is also very im- Receiving distance ing parameters for preparing PLA/PCL portant to form an electrospinning mem- The receiving distance refers to that be- microfibres waas decided by observing brane. tween the needle tip and the target. Ta- the electrospinning membranes’ sur- ble 2 presents the fibre’s average diam- face. The SEM technique and statistical Structure and property characterisa- eter and deviation of PLA/PCL microfi- method were used to evaluate the fibres’ tions of microfibre membranes As a result of experimental studies, the following parameters were selected: a) b) a PLA/PCL blending ratio of 70/30, DCM: DMF ratio of 4:1, a solution concentration of 8%, voltage of 12 kV, receiving distance of 15cm, and feed rate of 0.6ml/h. PLA, PCL and PLA/PCL microfibre membranes were prepared using the parameters above and their structure and performance were tested.

Surface structure and pore-diameter Figure 3. Scanning electron micrographs of PLA/PCL microfibre membranes at different Scanning electron micrographs of PLA, receiving distances (collected for 30 min), receiving distance: a) 15 cm, b) 27 cm. PCL and PLA/PCL microfibres are pre-

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d) e)

Figure 4. Scanning electron micrographs of PLA/PCL microfibre membranes with different blending ratios; a) PLA/PCL = 90/10, b) PLA/PCL = 80/20, c) PLA/PCL = 70/30, d) PLA/PCL = 60/40, e) PLA/PCL=50/50.

sented in Figure 6. Their pore-diameter However, PLA fibres (Figure 6.a) had 6.c). However, PCL and PLA/PCL fibres distribution histograms are shown in larger variations and presented a more were observed as more regular struc- Figure 7. As Figure 6 shows, three irregular structure when compared with tures. PLA, PCL and PLA/PCL polymers samples possess similar morphologies. the other two samples (Figure 6.b & were electrospun as a film-like surface

a) - average diameter 412.9 nm 0.40

0.35 b)Average - average Diameter: diameter 384.3nm 384.3 nm

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Frequency distribution 0.05

0.00 200 250 300 350 400 450 500 550 Fibre diameter, nm FiberFibre Diameter(nm)diameter, nm

c) - average diameter 395.8 nm

Figure 5. Fiber-diameter distribution of PLA/ Frequency distribution PCL=70/30, PLA and PCL single component membranes using the same electropinning parameters; a) PLA - average diameter 412.9 nm, b) PLA/PCL - average diameter 384.3 nm, c) PCL - average diameter 395.8 nm. Fibre diameter, nm

FIBRES & TEXTILES in Eastern Europe 2016, Vol. 24, 3(117) 21 a) b) c)

Figure 6. Scanning electron micrographs of PLA, PCL & PLA/PCL microfibre membranes; a) PLA, b) PCL, c) PLA/PCL.

0.35 0.25 b)Average - average pore pore diameter:1.55μm diameter 1.55 mm a)Average - average pore porediameter: diameter 3.17μm 3.17 mm

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0.00 0.00 1.5 2.0 2.5 3.0 3.5 4.0 4.5 0.5 1.0 1.5 2.0 2.5 3.0 PorePore diameter, Diameter(μm) mm PorePore diameter, Diameter(μm) mm

c) - averageAverage pore diameter: diameter 1.93μm 1.93 mm

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Figure 7. Membrane pore diameter distribution of 0.05 PLA, PCL and PLA/PCL; a) PLA - average pore diam- Frequency Distribution eter 3.17 mm, b) PCL - average pore diameter 1.55 mm, Frequency distribution c) PLA/PCL - average pore diameter 1.93 mm. 0.00 0.8 1.2 1.6 2.0 2.4 2.8 3.2 PorePore Diameter(μm) diameter, mm

with numerous micropores. As Figure 7 between 2 and 3 μm (Figure 7.c). Sev- morphologies of regular structure, while shows, PLA membranes possessed the eral maximum values are presented in PLA had a larger irregular structure with widest pore-diameter distribution, rang- Figures 7 histograms, which is because a larger pore diameter. PLA was difficult ing from 1 to 5 μm, with w larger aver- microfibres were deposited in a -disor to be made into microfibres, as there al- age pore diameter (Figure 7.a). PCL’s derly fashion, which led the pore size to ways existed large fibres of relative high pore-diameter concentration was dis- be distributed in a relatively wide range, irregularity. On the other hand, PCL is tributed from 0.5 to 3 μm (Figure 7.b). with more than one peak obtained as a re- more suitable to be made into microfi- PLA/PCL’s pore diameter changed from sult. The final conclusion was that PCL bres. Adding PCL to PLA can improve 0.6 to 3.2 μm, but was more focused and PLA/PCL microfibres show similar its spinnability and own membranes with irregular fibres. Table 3. Water absorption and contact angle of PLA, PCL, PLA/PCL electrospun membranes. Hydrophilicity and water absorption Table 3 provides the contact angle and Sample Water absorption, % CVwa, % Contact angle, deg CVca, % water absorption degree of three sam- PLA 2.68 2.68 139 1.09 ples in a PBS environment for 24 hours. PCL 62.96 4.67 133 0.56 PBS is a kind of buffer solution which PLA/PCL 101.90 5.02 125 0.60 is used to maintain the PH value around

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Figure 7. Scanning electron micrographs of PLA, PCL and PLA/PCL membranes after immersed in PBS solution for 24 hours; a) PLA, b) PCL, c) PLA/PCL.

a) b) Intensity, a.u. Intensity, Intensity, a.u. Intensity,

2 theta, deg 2 theta, deg

c) Intensity, a.u. Intensity,

Figure 8. XRD patterns of selected materials, showing the relative positions of diffraction peaks; a) PLA, b) PCL & c) PLA/PCL. 2 theta, deg the samples. CV listed in Table 3 means the PBS environment to enter into the between fibres. While PLA/PCL - mem the coefficient of variation, which was inner layers of the electrospun PLA mi- branes had the highest water absorption used to measure the variation degree of crofibres in a short time. The water ab- and almost maintained fibrous character- data. PLA, PCL and PLA/PCL composite sorption of fibres lead to a little swelling, istics in the membranes. membranes are all hydrophobic materi- which may have effect on morphologies. als; the contact angles 3 samples were The fibrous surface feather with no beads Crystallinity and thermal performance as follows: PLA > PCL > PLA/PCL. and regular structure is suitable for appli- Figure 8 shows the X-ray diffraction pat- Blending two materials together leads to cation in tissue engineering. Hence little tern of three samples. The degree of crys- a small decrease in the contact angle. or entirely no differences were expected tallinity of PLA, PCL & PLA/PCL sam- after immersion in the PBS environment. ples were 31.43%, 54.65% and 17.34%, Figure 7 shows the morphology of PLA, PLA membranes absorbed almost no respectively. PLA/PCL composite mem- PCL and PLA/PCL membranes after be- water and the fibre remained the same branes possessed the smallest degree of ing immersed in PBS for 24 hours. On compared to before immersion. PCL’s crystallinity, and PLA had 2 diffraction the basis of Table 3, PLA had the lowest water absorption rate was much bigger peaks (31, 14) detected at 2θ = 16.4° and water absorption degree, which is due to than that of PLA, which was 62.96%, but 22.6°, respectively. Their correspond- the higher crystallinity. It is difficult for there was a slight swelling and adhesion ing d-spacing values were determined

FIBRES & TEXTILES in Eastern Europe 2016, Vol. 24, 3(117) 23 n Conclusions a) PLA In this study, PLA/PCL microfibre mem- b) PCL branes were prepared by the electrospin- c) PLA/PCL ning process. In order to obtain nonwoven fabric with a distribution of diameters from 200-400 nm, the following parameters of formation were selected: a ratio of PLA/PCL of 70/30, solvent ratio of DCM:DMF of 80/20, a solution concentration of 8%, voltage of 12 kV, Heat flow endo up, mW receiving distance of 15 cm, and feed rate of 0.6 ml/h. In the above condition, the PLA/PCL membranes had fibres with an average diameter of 384.3 nm and a concentration distribution between 200 Temperature, °C to 400 nm. Figure 9. DSC curves of PLA, PCL, PLA/PCL. To demonstrate that the addition of PCL to PLA polymer can improve the microfi- Table 4. Tensile strength and elongation of PLA,PCL,PLA/PCL membranes. bre membranes’ properties and structure,

Sample Tensile strength, MPa CVts, % Elongation at break, % CVeb, % several experiments including the SEM, PLA 2.01 14.47 82.20 13.31 DSC, XRD, water contact angle, water PCL 1.54 14.77 108.72 18.12 absorption degree and tensile strength PLA/PCL 7.22 13.68 109.22 12.28 were carried out. The results obtained from morphology and pore-size evalu- as 0.54 and 0.39 nm (Figure 8.a). As for one melting peak existed. The peak val- ation revealed that PCL and PLA/PCL PCL samples, there are different diffrac- ues in the PLA and PCL curves were samples had a smaller pore size (1.55 and tion peaks(1330, 453, 51, 39) detected 166.29 °C and 58.57 °C, corresponding 1.93 μm) and average fibre diameter. Wa- at 2θ = 21.4, 23.8, 29.9, 40.3°. The d- to the melting points of these two mate- ter contact angle and absorption degree spacing of PCL samples are 0.41, 0.37, rials, respectively. There were two peak data showed that PCL’s addition to PLA 0.30 and 0.40 nm (Figure 8.b). PLA/PCL values existing in the PLA/PCL curve contributed to improving the samples’ samples have 4 diffraction peaks (97, 27, hydrophilicity. From the thermal evalua- 340, 117) with corresponding 2θ = 16.9, which equal the melting points of PLA tion, two melting peaks in the PLA/PCL 19.3, 21.5, 23.8° (Figure 8.c). The crys- and PCL polymers, thus the two materi- tal peaks of PLA were less obvious with als were distributed evenly in the com- DSC’s curve were found corresponding a low absorption intensity, showing more posite membranes. to the two components’ melting points. amorphous scattering. This may due to The PLA/PCL’s degree of crystallinity the different degrees of molecule defor- Mechanical properties was found to be much lower than that of PLA and PCL from the XRD test. The ten- mation during the electrospinning pro- Table 4 presents the tensile performance cess [14]. PCL had two sharp crystal sile test showed that PLA had a high ten- of PLA, PCL and PLA/PCL. It is gener- peaks with strong absorption intensity, sile strength but with low elongation, and ally believed that PLA possesses a high which lead to a high degree of crystal- that PCL possessed excellent elongation linity. The PLA/PCL materials’ diffrac- tensile strength but low toughness, while with poor strength, while the PLA/PCL tion pattern had features of both PLA and PCL has excellent elongation but poor composite membranes’ strength was PCL i.e., wide amorphous scattering and strength. The results show that PLA’s much larger than that of PLA, with an obvious peak, but the absorption in- strength was superior to that of PCL; but an elongation similar to PCL. Therefore tensity of the three peaks were not high. PLA’s elongation was low. PLA/PCL the PLA/PCL microfibre membrane was composite membranes showed the high- a composite material with high strength By adding low molecular-weight PCL est tensile strength, with an elongation and high elongation. Finally, in obtain- polymers to PLA, the membranes’ degree of crystallinity decreased sharply, similar to PCL’s. As is well noted in the ing smooth and relatively fine PLA/PCL and the relatively high amorphous mor- literature [19 - 21], there existed relative microfibre of small fibre diameter and phology was suitable for improving drug slippage between the PLA and PCL poly- regular structure, the addition of PCL to loading efficiency and promoting drug mers during the process of fibre stretch- PLA polymer had significant effects on release [18]. Moreover the low degree of ing, which effectively prevented the fibre the morphology structure, hydrophilicity, crystallinity can shorten the degradation tensile effect. In addition, there existed crystallinity and mechanical property. time, which solved the problem of PLA forces between PLA and PCL materials and PCL’s long degradation. such as the van der Waals force and so Figure 9 shows DSC curves of PLA, on, which also prevented fibre stretching Acknowledgements PCL and PLA/PCL microfibre mem- and enhanced the effect of the composite Sponsoring fund: National key technology branes. For PLA and PCL samples only membranes’ mechanical properties. R&D program (Grant No. 2012BAI17B05).

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INSTITUTE OF BIOPOLYMERS AND CHEMICAL FIBRES LABORATORY OF METROLOGY

Contact: Beata Pałys M.Sc. Eng. ul. M. Skłodowskiej-Curie 19/27, 90-570 Łódź, Poland tel. (+48 42) 638 03 41, e-mail: [email protected] AB 388 The Laboratory is active in testing fibres, yarns, textiles and medical products. The usability and physico-mechanical properties of textiles and medical products are tested in accordance with European EN, International ISO and Polish PN standards. Tests within the accreditation procedure: n linear density of fibres and yarns,n mass per unit area using small samples, n elasticity of yarns, n breaking force and elongation of fibres, yarns and medical products, n loop tenacity of fibres and yarns,n bending length and specific flexural rigidity of textile and medical products

Other tests: n for fibres: n diameter of fibres,n staple length and its distribution of fibres,n linear shrinkage of fibres,n elasticity and initial modulus of drawn fibres,n crimp index, n tenacity n for yarn: n yarn twist, n contractility of multifilament yarns,n tenacity, n for textiles: n mass per unit area using small samples, n thickness n for films: n thickness-mechanical scanning method, n mechanical properties under static tension n for medical products: n determination of the compressive strength of skull bones, n determination of breaking strength and elongation at break, n suture retention strength of medical products, n perforation strength and dislocation at perforation

The Laboratory of Metrology carries out analyses for: n research and development work, n consultancy and expertise

Main equipment: n Instron tensile testing machines, n electrical capacitance tester for the determination of linear density unevenness - Uster type C, n lanameter

FIBRES & TEXTILES in Eastern Europe 2016, Vol. 24, 3(117) 25