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首页> 外文期刊>Journal of Applied Polymer Science >Isotactic Polypropylene/Ethylene-co-Propylene Blends: Influence of the Copolymer Microstructure on Rheology, Morphology, and Properties of Injection-Molded Samples
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Isotactic Polypropylene/Ethylene-co-Propylene Blends: Influence of the Copolymer Microstructure on Rheology, Morphology, and Properties of Injection-Molded Samples

机译：全同立构聚丙烯/乙烯-丙烯共混物：共聚物的微观结构对注塑样品的流变学，形态和性能的影响

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Melt rheological behavior, phase morphology, and impact properties of isotactic-polypropylene (iPP)-based blends containing ethylene-propylene copolymer (EPR) synthesized by means of a titanium-based catalyst with very high stereospecific activity (EPP_Ti) were compared to those of iPP/EPR blends containing EPR copolymers synthesized by using a traditional vanadium-based catalyst (EPP_V). The samples of EPR copolymers were synthesized ad hoc. They were characterized by comparable propylene content, average molecular masses, and molecular mass distribution in order to assess the effects of distribution of composition and sequence lengths of the structural units on the strucutre-properties correlations established in the melt and in the solid state while studying different iPP/EPR pairs .~1-5Differential scanning calorimetry ,(DSC), wide-angle X-ray spectroscopy (WAXS), small-angle X-ray (SAXA), and scanning electron microscopy (SEM) investigations showed that the EPR_Ti chain is characterized by the presence of long ethylenic sequences with consititutional and configurational regularity required for crystallization of the polyethylene (PE) phase occuring, whereas a microstrucutre typical of a random ethylene-propylene copolymer was exhibited by the EPR_V copolymer. The different intra- and intermolecular homogeneity shown by such EPR phases was found to affect their melt rheological behavior at the temperatures of 200 and 250 deg C; all the EPR-Ti dynamic-viscielastic propreties resulting were lower than that shown by the EPR_V copolymer. As far as the melt rheoligical behavior of the iPP/EPR_Ti blends was concerned, both the iPP/EPR pairs are to be classified as "negative deviation blends" with G' and G'' values higher than that shown by the plain components. The extent of the observed deviation in the viscosity values and of the increase in the amounts of stored and dissipated energy shown by such iPP/EPR pairs was found to be dependent on copolymer microstruucutre, being larger for the melts containing the EPR_Ti copolymer. The application of the Cross-Bueche equaiton also confirmed that, in absence of shesr,the melt phase viscosity ratio is the main factor in determining the viscosity of iPP/EPR blends and their viscoelastic parameters. The general correlation estabished between EPR disperstion degree (range of particle size and number-average particle size), as determined in injection-molded samples, and melt phase viscosity ratio (#mu#) was ratified; the type of dependence of EPR size upon #mu# value was in qualitative agreement with the prediction of the Taylor-Tomotika theory. Contrary to expectation, ~1-5 for test temperature close to iPP T_g, EPP_V paraticles ranging in size between 0.75 and 1.25 #mu#m resulted and were more effective than EPP_Ti particles, ranging in size between 0.25 and 0.75 #mu#m, in promoting multiple craze formation. Also taking into account the SAXS results, reveaked that the molecular supersturcture (i.e., crystalline lamellar thickness and amorphous interlayer) of the iPP matrix is unaffected by both the presence of EPP_Ti and EPR_V phase. The above finding was related to the ethylenic crystallinity degree shown by the EPP_Ti copolymer. In perticular, such a degree of crystallinity was supposed to deteriorate toughening by decreasing the tie molecules density in the EPP_Ti domains, notwithstanding the beneficial effect of the ethylenic lamellar buildup. For test temperature close to room temperature, the ductile behavior exhibited by the iPP/EPR_Ti blends was accounted for by a predominant shear yielding fracture mechanism probably promoted by a high concentraion of interlamellar tie molecules among iPP crystallites in agreement with DSC results. Nonisothermal crystallization experiments showed, in fact, that the crystallization peak of the iPP phase from iPP phase from iPP/EPR_Ti melt is shifted to higher temperatures noticeably, thus indicating a material characterized by a comparatively h
机译：将通过具有很高立体定向活性（EPP_Ti）的钛基催化剂合成的含乙烯-丙烯共聚物（EPR）的等规聚丙烯（iPP）基共混物的熔体流变行为，相形态和冲击性能进行了比较。包含使用传统钒基催化剂（EPP_V）合成的EPR共聚物的iPP / EPR共混物。 EPR共聚物的样品是临时合成的。它们的特征是具有可比的丙烯含量，平均分子量和分子量分布，以便在研究时评估组成分布的分布和结构单元的序列长度对在熔体和固态中建立的结构性能相关性的影响。不同的iPP / EPR对。〜1-5差示扫描量热法（DSC），广角X射线光谱法（WAXS），小角度X射线（SAXA）和扫描电子显微镜（SEM）研究表明，EPR_Ti链的特征在于存在长的乙烯序列，其具有发生聚乙烯（PE）相结晶所需的组成性和构型规则性，而EPR_V共聚物表现出典型的无规乙烯-丙烯共聚物的微结构。发现这种EPR相显示出的不同的分子内和分子间均质性会影响其在200和250℃的温度下的熔体流变行为;所产生的所有EPR-Ti动态粘弹性性能均低于EPR_V共聚物显示的性能。就iPP / EPR_Ti共混物的熔体流变行为而言，两个iPP / EPR对均应归类为“负偏差共混物”，其G'和G''值高于普通组分所显示的值。已经发现，这种iPP / EPR对显示的粘度值的偏差程度以及所储存和耗散能量的增加量取决于共聚物的微观结构，对于包含EPR_Ti共聚物的熔体而言更大。 Cross-Bueche等式的应用还证实，在没有shesr的情况下，熔融相粘度比是确定iPP / EPR共混物的粘度及其粘弹性参数的主要因素。批准了在注塑样品中确定的EPR分散度（粒径范围和数均粒径）与熔融相粘度比（＃mu＃）之间的一般相关性; EPR大小对＃mu＃值的依赖性类型与Taylor-Tomotika理论的预测在质量上一致。与预期相反，测试温度接近iPP T_g约1-5，EPP_V微粒的尺寸范围在0.75至1.25＃mu＃m之间，并且比EPP_Ti粒子的尺寸范围在0.25至0.75＃mu＃m之间更有效，在促进多重热潮的形成。还考虑到SAXS结果，表明iPP基质的分子超结构（即晶体层厚度和无定形中间层）不受EPP_Ti和EPR_V相的存在的影响。上述发现与EPP_Ti共聚物显示的烯属结晶度有关。在垂直方向上，尽管烯属层状堆积的有益作用，但据认为，这种结晶度会通过降低EPP_Ti域中的键分子密度而恶化增韧。对于接近室温的测试温度，iPP / EPR_Ti共混物表现出的延展性是由主要的剪切屈服断裂机制引起的，这可能是由于iPP微晶中高浓度的层间键合分子与DSC结果一致所促进的。非等温结晶实验表明，实际上，来自iPP / EPR_Ti熔体的iPP相的iPP相的结晶峰明显转移到了较高的温度，因此表明材料的特征是相对h

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