Study on composition and characteristics of maleated ethylene-octene copolymer prepared by reactive extrusion on the morphology and properties of polyamide 6/ethylene-octene copolymer blends.
Toughening of polyamide (PA) with elastomeric materials has been of considerable commercial and scientific interest. Commonly used elastomers are ethylene-propylene copolymer (EPM) (1-5) and ethylenepropylene diene terpolymer (EPDM) (5). Properties of these blends depend on several factors, especially blend composition, size and shape of the dispersed particles, the glass transition temperature of the dispersed phase, and the interfacial adhesion between the dispersed and matrix phases. Owing to high polarity differences, these blends are immiscible and often exhibit poor mechanical properties. The problems of incompatibility can generally be overcome by the incorporation of either a block or graft copolymer having segments that may interact with each polymer component, or a functionalized polymer that reacts with one or both polymers, leading to in-situ compatibilization during the mixing process. The most widely used compatibilizers include maleic-anhydride modifled EPM (2-4), maleic-anhydride modified EPDM (5), maleic-anhydride modified polystrene-block-poly(ethylene-butylene)-block-polystyrene (SEBS-MA) (6). It was demonstrated that the anhydride groups of rubber undergo chemical reactions with the amine groups of PA during melt blending (7, 8). The reaction between MA containing polymer and PA6 has been well established (7-10). The use of MA grafted polymers caused a reduction of the dispersed particle size in the blends and led to a dramatic improvement in impact strength (3-6). Thomas and Groeninckx (3) observed that the addition of EPM-MA compatiblizer reduced the domain size of the EPM dispersed phase in the PA6 blends. The reduction of domain size is a function of compatibilizer content. The finest marphology was obtained by preblending the compatibilizer with the EPM phase and then mixing with the PA6 matrix phase.
In this study, metallocene produced ethylene-octene copolymer (EOR) was selected as an impact modifier for polyamide 6 (PA6). It was found also to be more effective than traditional modifiers such as EPDM in improving the impact strength of polypropylene (PP) and its filled composites (11-13). Blends of PA6 and EOR were investigated over a range of compositions. In order to improve the compatibility between the PA6 matrix and the EOR phase, EOR modified by grafting with maleic anhydride (EOR-MA) was used. EOR-MA was prepared in our laboratory by reactive extrusion. During the grafting of MA onto EQR. crosslinking and/ or degradation of EOR may take place. The amount of crosslink or gel and of MA grafted on the EOR could possibly affect the morphology and properties of the blends. The aim of this work is, therefore, to study the influence of EOR-MA characteristics and composition on the phase morphology, thermal and mechanical properties of PA6 blends.
Polyamide 6 (PA6) grade F223-D supplied by DSM Engineering Plastics Co. Ltd. was used as a matrix polymer. The ethylene-octene copolymer (EOR) used was Engage 8150, DuPont Dow Elastomer Co., containing 25 wt% octene comonomer with a melt flow rate of 0.5 g/10 min(190[degrees]C/2.16 kg) and a density of 0.868 g/[cm.sup.3]. Maleated EOR (EOR-MA) was prepared by free radical grafting of Engage 8150 using reactive extrusion.
Preparation and Characterization of EOR-MA
Melt grafting of maleic anhydride (MA) onto EOR was carried out in a Prism TSE 16 intermeshing co-rotating twin-screw extruder, in the presence of dicumyl peroxide (DOP) as an initiator ([t.sup.1/2]= 14.5 sec at 190[degrees]C). Dimethyl formamide (DMF) was used as an inhibitor to reduce crosslinking and as a solvent for peroxide initiator. The extruder was equipped with liquid injection ports and a vacuum port, and screws 16-mm diameter and an effective length of 400 mm. The screws were assembled from individual screw elements, including regular helical shaped screw profiles, kneading blocks and mixing elements for providing good conveying and mixing in the extruder. The screw configuration used is shown elsewhere (14). The EOR pellets, precoated with a known amount of MA powder, were fed to the extruder by a K-Tron volumetric feeder. The dicumyl peroxide initiator was introduced into the extruder as a solution in dimethyl formamide, using a liquid addition pump (SAGE Instruments model 355). The temperature profile f rom feed zone to die was set in the range from 100 to 190[degrees]C, respectively. A screw speed of 100 rpm was used. This gave a total residence time of approximately 2 mm. The final reaction products exiting from a die were cooled in a water bath and pelletized.
The chemical structure of EOR-MA was characterized by means of infrared spectroscopy (FTIR). Figure 1 shows FTIR spectra of EOR and EOR-MA over a frequency range of 3400 to 600 [cm.sup.-1]. The strong bands at 2975 and 2915 [cm.sup.-1] correspond to -[CH.sub.3], -[CH.sub.2] asymmetric and symmetric stretching vibrations in the elastomers. The bands at 1459 and 1377 [cm.sup.-1] are the characteristics of -[CH.sub.3] asymmetric, -[CH.sub.2] symmetric and -[CH.sub.3] symmetric deformation vibrations, respectively. Another band appearing at 720 [cm.sup.-1] is attributed to long ethylene sequence [(-[CH.sub.2]-).sub.n], n[greater than or equal to] 5, rocking vibration. Additional bands are observed in the EOR-MA spectrum. The new bands corresponding to the cyclic anhydrides are clearly seen at 1867 and 1792 [cm.sup.-1]. A strong band at 1792 [cm.sup.-1] was reported earlier to be a reflection of alkyl succinate units on the polymer chains (15, 16).
The amount of grafted MA in the reaction products was determined by titrating the acid groups after hydrolysis of the anhydride groups. This can be obtained by dissolving the reaction products in xylene and then refluxing with water-saturated xylene for 2 hrs. The hot solution was titrated Immediately with 0.02 N tetramethyl ammonium hydroxide in ethanol (TMA) using 1-2 drops of thymol blue (1%) in DMF as an indicator. The percentage of grafting was calculated using the following equation.
% MA grafted = N V X M/2/weight of EOR-MA (1)
where: N and V are concentration and volume of TMA, respectively
M is molecular weight of maleic anhydride
The gel contents or insoluble fractions of the reaction products were measured by a solvent extraction technique, according to ASTM D 2765-95a. Samples were placed in 120 mesh stainless-steel cages and immersed for 6 his in boiling xylene containing 1% of antioxidant (Irganox 1010, Ciba-Geigy). The samples, after removal from the boiling solvent, were dried in a vacuum oven until constant weight was reached. The gel content was then calculated as the weight fraction of the insoluble portion. The details of EOR-MA preparation and characterization are reported in Ref. 14.
Various PA6 blends were prepared by melt-mixing the components in a co-rotating twin-screw extruder. The screw used for mixing was the same as that used for grafting. The materials were dried in a vacuum oven at 80[degrees]C for 6 his prior to blending. The barrel temperature profile was set between 200 and 230[degrees]C (from feed zone to die). The screw speed used was 100 rpm, giving a throughput rate of 1.5 kg/hr. Test specimens for tensile and Impact tests were prepared by in Jection molding, using a barrel temperature of 230[degrees]C.
Structural Analysis and Mechanical Testing
The phase morphology of PA6 blends was examined using a Hitachi S2500 scanning electron microscope. Specimens were prepared by cryogenic fracturing and etching out the elastomer phase with hot heptane vapor for 20 sec. The specimens were dried and then coated with platinum-palladium prior to viewing under SEM. The SEM micrographs were then used to analyze the dispersed particle size, shape and size distribution. The analysis was carried out using a computerized image analyzer with Image-Pro Plus software. Typically, over 300 particles and several fields of view were measured. The number average rubber particle sizes ([d.sub.n]) in the blends were calculated using the following equation (17).
[d.sub.n] = [N.sub.t=1][n.sub.t][d.sub.t]/[N.sub.t=1][n.sub.t] (2)
The melting and crystallization behaviors of the blends were studied using a Perkin-Elmer DSC-7 differential scanning calorimeter. Samples were first heated from 50 to 260[degrees]C at a scan rate of 10[degrees]C/min and then maintained at 260[degrees]C for 5 min before cooling to 50[degrees]C at the same rate. The percentage crystalinity of the blends was calculated from the heat of fusion using [DELTA]H[degrees] value of 190 J/g (18).
Tensile properties were measured in accordance with ASTM D638-83, using an Instron Model 4301 tensile testing machine with a crosshead speed of 50 mm/min. A load cell of 5 kN was used. Izod impact strength was obtained from notched specimens, using a Zwick impact tester. A 4 Joule pendulum-type hammer was used. Fifteen specimens were analyzed for each composition. All mechanical testing was undertaken at 23[degrees]C.
RESULTS AND DISCUSSION
Non-reactive PA6 Blends (Without EOR-MA)
Figure 2 shows SEM micrographs of PA6/EOR blends of various compositions. The two-phase morphology is clearly visible at all compositions. The droplets of EOR dispersed randomly within the PA6 matrix. No evidence of adhesion at the interface between PA6 and EOR was observed. The number average diameter ([d.sub.n]) of EOR particles was in the range of 4-13 [micro]m, depending on the concentration of EOR in the blends (Fig. 3). Increasing the EOR concentration resulted in an increase of EOR particle size and size distribution. The increase in dispersed particle size may be associated with the coalescence of dispersed EOR particles at high EOR concentration. For polymer blend systems, the final morphology is a result of balance of domain breakup and coalescence at the end of mixing. With increasing concentration of the rubber phase in the blend, the number of rubber particles increased, and as a consequence, a tendency of coalescence increased. In PA6/EPM blends, the coalescence was reported to be more prominent when EPM was the dispersed phase (3).
Table 1 shows the DSC results of PA6 and PA6/EOR blends. The melting ([T.sub.m]), and crystallization temperature ([T.sub.c]), enthalpy of fusion ([DELTA][H.sub.f]), percentage of crystallinity (%C) and percentage of normalized crystallinity (%N) of PA6 and PA6/EOR blends are summarized. PA6 shows a [T.sub.m] peak at approximately 218[degrees]C. The observed enthalpy of fusion is 73.9 J/g, which leads to an estimated crystallinity of 39% with a quoted value of 190 J/g for fully crystalline PA6 (18). The EOR, though, has the ability to crystallize. Under the studied conditions, however, no melting and crystallization peak of EOR was seen. [T.sub.m] of EOR could be observed at ~55-60[degrees]C after a long annealing time. The melting ([T.sub.m]) and crystallization temperature ([T.sub.c]) of PA6/EOR blends barely changed with blend composition. Similar findings were reported in PA6/PE blends (2, 19). This suggested that PA6 and EOR are completely immiscible. No effect of EOR on the crystallization of PA6 was ob served. The onset temperature of crystallization ([T.sub.c onset]) of PA6 blends appeared at ~194[degrees]C, which is similar to that observed in pure PA6. Increasing the EOR content led to a systematic decrease in [DELTA][H.sub.f] and percent of overall crystallinity. However, this was due to the dilution of PA6 in the blends. By recalculating the percent crystallinity based on weight percent of PA6 in the blends (the percent normalized crystallinity), no significant difference in these values was observed.
Table 2 shows the dependence of tensile properties on the EOR content in the blends. An increase of EOR content led to a linear decrease in blend modulus, stress at yield and at break. These observations are generally found in various incompatible blends and have been reported to be due to the softening or diluting effect of the second component (19-21). Contrary to those properties, the elongation at break was found to increase slightly with increasing EOR concentration.
The notched Izod impact strength of the blends as a function of EOR concentration is Illustrated in Fig. 4. Compared to brittle materials as polystyrene (PS), PA6 is defined as a pseudoductile polymer because of its high crack initiation energy but low crack propagation energy (19, 21). This causes PA6 to have a high unnotched but a low notched impact strength. The notched impact strength of 55 J/m was observed in pure PA6 sample. The incorporation of 10% EOR led to a significant improvement in impact strength. The PA6 blend containing 20% EOR exhibited the highest impact strength of 100 J/m, which is double that of pure PA6. Further increase of EOR content, however, caused a drop of this property. A reduction in impact strength at high rubber content (> 20%) was believed to be partly due to the improper size of the EOR particles in the blends. The SEM studies showed an increase in EQR particle sizes at high rubber loadings (Figs. 2 and 3). In PA6/EPDM blends, Borggreve et al. found a shift of the brittle-duc tile transition temperatures to lower values as the particle size of EPDM decreased (5). The impact strength in the brittle region was higher when the average particle size was smaller. However, the effect of particle size on impact property was very small in the tough region. To achieve super-toughness for PA6, a rubber particle size below 1 [micro]m has been reported (6).
Reactive PA6 Blends (With EOR-MA)
From the work on non-reactive PA6/EOR blends, the blend containing 20% EOR exhibited the highest impact strength. This dictated the selection of this rubber content for this experiment. Therefore, the reactive PA6 blends are prepared by keeping the volume percent of PA6 constant at 80%, whereas the percentage of EQR and EQR-MA were varied in the range of 0%-20%.
The strong influence of EOR-MA on the morphology of PA6 blends can be seen from Fig. 5. Comparing Fig. 5a to 5c, the substitution of EOR by EOR-MA led to a significant change in the phase morphology owing to its in-situ compatibilizing effect. The blend containing 20% EOR-MA (Fig. 5c) shows a morphology of very fine particles with [d.sub.n] of 0.3 [micro]m, which is nearly twenty times smaller than those observed in the blend of unmodified EOR (6.1 [micro]m) of the same composition (Fig. 5a). During melt blending, the formation of a chemical interaction at the interface between the anhydride group of MA and the amine group of PA6 ((EOR-MA)-g-PA6) may occur and lead to a strong adhesion between the rubber particles and the PA6 matrix. Similar findings have been reported for PA6/EPM blends (7, 8). The enthalpy of the system that drove the (EPM-MA)-g-PA6 to the interface was reported to cause an increase in interfacial area and a reduction in rubber particle size (9). In the blend containing both EOR and EQR-MA of equal amount of 10% (80/10/10), Figure 5b reveals the morphology with the number average particle size of 0.6 [micro]m, which is between those of PA6/EOR and PA6/EOR-MA blends.
DSC results of PA6 and its blends containing EORMA are shown in Table 3. As mentioned earlier and seen in Table 1, unmodified EOR hows no effect on crystallization behavior of PA6. [T.sub.m], [T.sub.c onset], [T.sub.c] and percent normalized crystallinity of PA6/EOR blends are similar to those of PA6. Different results were found when EOR-MA was incorporated. [T.sub.m] and [T.sub.c] decreased with increasing EOR-MA content. Similar results were reported to be due to the chemical reaction of terminal amino groups of PA6 with anhydride groups of maleic-anhydride grafted polymer, resulting in a decrease of the segmental mobility of the polyamide chains and also hindering polymer chain packing so that the perfection of the PA6 crystal is reduced (10, 22). Yao et al. found similar results, and the reason was reported to be the weakening of hydrogen bonds among the molecular chains of PA6. It Is known that the crystallization of PA6 comes mainly from hydrogen bond interaction of intra or inter-molecular chains; weakening of the hydrogen bond interaction in the presence of maleic anhydride modified polymer may inhibit its crystallization (23). Another possible reason for the evolution in [T.sub.m] may be the fact that the water molecules, generated from the coupling reaction between PA6 and anhydride groups of MA, hydrolyze PA6 main chains and then cause a lowering in PA6 molecular weight. As a consequence, a reduction in PA6 melting temperature was observed.
Effect of gel and MA content in EOR-MA. During the grafting of maleic-anhydride (MA) onto EOR, cross-linking and/or degradation of EOR may occur. Therefore, this part of work Is aimed at investigating the effects of crosslink (gel) and MA contents in EOR-MA on the mechanical properties of PA6 blends.
Figures 6a to 6d show the effects of content of gel or crosslinking product on the tensile properties of the blends. Modulus and tensile stress at break of the blends containing EOR-MA of different gel contents vary slightly within standard deviation. In other words, the degree of crosslink (in the range of 0%-27%) has a slight effect on modulus and tensile stress of PA6 blends. These results were similar to those found for PP/crosslinked rubber blends (24). Contrary to these results, a decrease in percentage of elongation at break was found when increasing the amount of gel in EORMA. The same trend was found for impact property. The impact strength of PA6 blends significantly decreased with an increase of gel content. These results are believed to be partly due to a high viscosity of crosslink rubber. Stress generated during blend preparation was unable to shear these crosslinks apart easily. The above results corresponded with the number average diameter of particles, which increased with an increase of ge l content (Fig. 7).
The effects of MA content in EOR-MA on the tensile and impact properties of PA6 blends are shown in Fig. 8. In this study, the gel content of EOR-MA was kept constant (~2%) in order to gain high impact resistance. It can be seen that the use of EOR-MA with the grafted MA content in the range of 0.5%-1.0% shows no significant difference in their effects on tensile and impact properties.
Effect of blend composition. Table 4 shows the tensile properties of various PA6 blends. The EOR-MA used in this investigation has 1% grafted MA with 1.8% gel. Compared to PA6, both EOR and EOR-MA are low-modulus materials. As expected, the incorporation of these components into PAG caused a reduction in modulus of the blends. From this study, EOR-MA had higher modulus (2.7 MPa at 100% strain) than unmodified EOR (2.3 MPa at the same strain). As a consequence, the blends containing EOR-MA should theoretically have higher moduli than those containing unmodified EOR. Experimentally, however, a contradictory result was found. In a similar work, Cimmino et al. found lower moduli in PA6/EPM/EPMg-SA blends, compared with PA6/EPM blends (8). The reason was reported to be the graft copolymer (EPM-gSA)-g-PA6 at the interfacial zones between PA6 and the dispersed particles, which caused an increase in free volume (8, 25). In the case of tensile stress, it was found that the values of tensile yield stress are always hig her than those of break stress for all blends. The blend containing EOR-MA shows lower stress values than that with unmodified EOR. All compositions have lower stress than pure PA6.
The opposite effect can be seen from the elongation values, where the use of EOR-MA led to a marked Increase of elongation at break. The increase in elongation suggested better stress transfer across the interfaces. In the reactive PA6/EOR-MA. system, the particles of EOR-MA were finely dispersed within the PA6 matrix. A number average diameter of 0.3 [micro]m was observed, compared to 6 [micro]m found for the non-reactive PA6/EOR blend of the same composition. In addition, the (EOR-MA)-g-PA6 that may occur at the interfaces of rubber particles could improve the compatibility between the PA6 matrix and the rubber phase.
Figure 9 shows a toughness enhancement of PA6 by the use of EOR-MA. In this study, the blend containing 20% EOR-MA exhibited an impact strength of 1000 J/m, which is twenty times higher than that of pure PA6 (55 J/m) or ten times higher than the use of unmodified EOR (100 J/m) of the same concentration. This indicates the effectiveness of EOR-MA as a toughening agent for PA6. As suggested by Collyer (26), a polymer matrix could be super-toughened if the impact strengths are higher than 530 J/m. The PA6/EOR-MA blend of this study, therefore, could be classified as a super-tough polymer. The presence of EOR-MA in the blends led not only to a drastic reduction in the rubber dispersed particle size, but also to some changes in fracture mechanisms in the blends, thus enhancing the impact resistance of the blends.
Figure 10 shows SEM micrographs of impact fractured surfaces of PA6 and its blends. The fractured surface of pure PA6 revealed a number of featherlike structures, which is the nature of brittle fracture (Fig. 10a). Addition of 20% EOR caused some changes to the fracture morphology. Owing to the poor adhesion between the EQR and the PA6 phases, cavitation of EOR particles can be clearly observed (Fig. lob). These cavities are evidently the source of the whitening observed in the sample. This, therefore, led to an enhancement in blend impact strength. An impact strength of 102 J/m was obtained in this blend, which is nearly double of that found for pure PA6 (55 J/m). As EOR was replaced by EOR-MA, the fracture surface of the blend became very rough. High magnification micrographs reveal both cavitation of rubber particles and a number of regular striations due to plastic deformation (Fig. 10c). A similar morphology was also observed in other rubber-toughened polymers such as PP/EOR blends (12, 13). In PA6/EOR-M A system, a twenty-fold improvement of impact strength was obtained, In the case of blend containing both EOR and EOR-MA, no shear yield of the PA6 matrix as observed in the PA6/ EOR-MA was found (Fig. 10d).
Blends of PA6 and EOR were investigated. A twophase morphology was observed. EOR droplets were randomly dispersed in the PA6 matrix without adhesion between the phases. The EOR particle sizes were found to increase with increasing concentration of EOR in the blends. The coalescence of particles was dominated at high rubber concentrations. Addition of EOR to PA6 resulted in a drop in tensile stress and modulus, whereas the Impact strength increased slightly.
Significant changes in blend morphology and mechanical properties were obtained when EOR-MA was employed. The rubber particle size drops from 6.1 [micro]m In PA6/EOR blends to 0.3 [micro]m in PA6/EOR-MA. blends of the same composition. A drastic reduction in dispersed particle size and an increase in adhesion between the phases, brought about by the reaction between amino groups of PA6 and anhydride groups of EOR-MA, were believed to be responsible for toughness enhancement of these blends. In this study, the blend containing 20% of EOR-MA exhibited twenty-fold improvement of impact strength, compared to pure PA6. High impact resistance was gained by the use of EOR-MA containing less than 2% gel. The contents of grafted MA in EOR in the range of 0.5%-l.0% showed no significant difference in their effects on tensile and Impact properties of the blends.
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Table 1 Melting Temperature ([T.sub.m]), Onset Temperature of Crystallization ([T.sub.c onset]), Crystallization Temperature ([T.sub.c]), Enthalpy of Fusion ([DELTA][H.sub.t]), Percent Overall Crystallinity and Percent Normalized Crystallinity of PA6 in Non-reactive Pa6/EOR Blends. PA6/EOR [T.sub.m] [T.sub.c onset] [T.sub.c] [DELTA][H.sub.t] (%vol) ([degrees]C) ([degrees]C) ([degrees]C) (J/g) 100/0 218.4 194.4 189.6 73.9 90/10 218.3 193.8 189.7 71.8 80/20 218.5 193.7 189.5 62.8 70/30 217.6 193.5 189.2 59.8 60/40 218.1 193.4 189.3 49.4 PA6/EOR Crystallinity Normalized (%vol) (%) crystallinity (%) 100/0 38.9 38.9 90/10 37.8 41.0 80/20 33.1 39.5 70/30 31.5 41.8 60/40 26.0 39.6 Table 2 Tensile Properties of Non-reactive PA6/EOR Blends. PA6/EOR Modulus Stress at Stress at Elongation at (%vol) (GPa) yield (MPa) break (MPa) yield (%) 100/0 2.88 (0.04) (a) 84.14 (1.03) 74.08 (0.87) 3.91 (0.07) 90/10 2.54 (0.03) 71.42 (0.83) 54.43 (1.77) 3.99 (0.10) 80/20 2.15 (0.01) 58.81 (0.65) 49.29 (0.97) 3.78 (0.10) 70/30 1.85 (0.01) 47.11 (0.66) 42.12 (0.69) 3.65 (0.06) 60/40 1.48 (0.01) 35.64 (0.40) 33.31 (0.35) 3.67 (9.52) PA6/EOR Elongation (%vol) at break (%) 100/0 7.57 (1.04) 90/10 7.47 (0.10) 80/20 8.76 (0.85) 70/30 8.49 (0.83) 60/40 9.52 (0.75) (a) Standard deviation in paranthesis. Table 3 Melting Temperature ([T.sub.m]), Onset Temperature of Crystallization ([T.sub.c onset]), Crystallization Temperature ([T.sub.c]), Enthalpy of Fusion ([DELTA][H.sub.f]), Percent Overall Crystallinity and Percent Normalized Crystallinity of PA6 in Reactive PA6/EOR/EOR-MA Blends. PA6/EOR/ [T.sub.m] [T.sub.c onset] [T.sub.c] [DELTA][H.sub.f] EOR-MA ([degrees]C) ([degrees]C) ([degrees]C) (J/g) 100/0 218.4 194.4 189.6 73.9 80/20/0 218.5 193.7 189.5 62.8 80/10/10 217.9 193.0 188.7 64.7 80/0/20 215.8 192.6 188.2 57.3 PA6/EOR/ Crystallinity Normalized EOR-MA (%) crystallinity (%) 100/0 38.9 38.9 80/20/0 33.1 39.5 80/10/10 34.1 40.6 80/0/20 30.2 36.0 Table 4 Tensile Properties of PA6/EOR/EOR-MA Blends. PA6/EOR/EOR-MA Modulus Stress at Stress at Elongation at (%vol) (GPa) yield (MPa) break (MPa) yield (%) 100/0/0 2.88 (0.04) (a) 84.1 (1.0) 74.1 (0.9) 3.9 (0.1) 80/20/0 2.15 (0.01) 58.8 (0.6) 49.3 (1.0) 3.8 (0.1) 80/10/10 1.60 (0.05) 49.9 (1.9) 38.4 (2.0) 4.1 (0.2) 80/0/20 1.75 (0.04) 48.6 (1.6) 39.5 (1.4) 4.0 (0.1) PA6/EOR/EOR-MA Elongation at (%vol) break (%) 100/0/0 7.5 (1.0) 80/20/0 8.8 (0.8) 80/10/10 22.3 (2.9) 80/0/20 25.2 (1.9) (a) Standard deviation in parantheses.
The authors are grateful to the National Metal and Material Technology Center (MTEC) for financial support.
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K. Premphet-Sirisinha *
* To whome correspondence should be addressed. E-mail: email@example.com.
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|Author:||Premphet-Sirisinha, K.; Chalearmthitipa, S.|
|Publication:||Polymer Engineering and Science|
|Date:||Feb 1, 2003|
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