具有高界面压应力的高分子共混物Ⅱ.拉伸过程中形态演化与增强机理

研究了聚对苯二甲酸乙二醇酯(PET)/聚乙烯(PE)和聚碳酸酯(PC)/PE共混物在拉伸过程中形态的演化和增强机理.结果表明,高界面压应力是共混物在基体加工温度成型时,从成型温度冷却到室温过程中基体收缩比分散相大产生的;两种共混物在拉伸中有不同的形态演化过程:PC粒子原位形成了微纤,粒子与基体间没有明显的界面滑动,而PET粒子只产生较小的塑性变形,成为椭球状粒子,粒子与界面间存在滑动.PC对基体PE的增强效果比PET的更好,因为PC/PE共混物拉伸过程中形成了良好增强作用的原位微纤.在拉伸过程中,PET/PE试样的细颈在靠近非浇口端形成,并从此扩展开.部分拉伸后,PC/PE试样比PET/PE试样的弹性回复大,回复到平衡状态时间长,这是两种共混物分散相变形机理不同引起的.     

云母/聚丙烯共混物熔体的拉伸流变性能

采用双料筒毛细管流变仪和Haul-off牵伸设备, 研究了云母(Mica)/聚丙烯(PP)共混物在拉伸流场中的流变性能。结果表明: Mica/PP共混物熔体拉伸流动属于拉伸变稀型, 随着云母含量的增加, 熔体的表观拉伸黏度逐渐增大。熔体的拉伸应力和表观拉伸黏度均随温度的升高而下降。随着拉伸应变速率的提高, 熔体的拉伸应力增大, 表观拉伸黏度减小, 熔体拉伸流动活化能呈下降趋势。云母微粒的加入使聚丙烯熔体的拉伸模量明显增大, 但随着拉伸速度的提高, 共混熔体的拉伸模量下降显著。为了提高Mica/PP共混物的纺丝稳定性, 应严格控制好拉伸速度和加工温度。     

拉伸挤出加工聚对苯二甲酸-己二酸-丁二醇酯/热塑性淀粉共混物的结构与性能

采用偏心转子挤出机制备了聚对苯二甲酸-己二酸-丁二醇酯(PBAT)/热塑性淀粉(TPS)共混物。通过与双螺杆挤出方式进行对比,研究了拉伸挤出对PBAT/TPS共混物形态结构、结晶结构、流变特性和力学性能的影响。结果表明,拉伸挤出加工促进了淀粉的塑化及在PBAT基体中的分散,强化了PBAT与TPS之间的界面相互作用。与双螺杆挤出共混物相比,拉伸挤出加工PBAT/TPS共混物的拉伸强度、断裂伸长率和冲击强度分别提高了19%,9%和28%。当TPS含量为40%时,拉伸挤出共混物拉伸强度仅比PBAT降低了29%,但其断裂伸长率与PBAT相当,冲击强度比PBAT提高了75%。偏心转子挤出机为制造低成本、高性能生物降解高分子材料提供了有效工具。     

PET/PE原位微纤化共混物的形态与性能

用“熔融挤出—热拉伸—淬冷”方法制备了聚对苯二甲酸乙二醇酯(PET)／聚乙烯(PE)原位微纤化共混物(MCB)，研究了热拉伸比恒定时组成对MCB形态和力学性能的影响，形态观察发现，MCB形成了良好的纤维结构，热拉伸比恒定时，纤维的形态特征(如直径及其分布等)主要受PET含量影响，MCB拉伸模量和强度较通常共混物有显著提高，但太低和太高PET含量，增强效果有所减弱，随着PET含量的提高，MCB经历了从韧性拉伸断裂到脆性拉伸断裂的转变。     

PET/PE原位微纤化共混物的非等温结晶

通过挤出、热拉伸及淬冷制备了聚对苯二甲酸乙二醇酯(PET)/聚乙烯(PE)原位微纤化共混物。采用差示扫描量热仪(DSC)研究了PET/PE原位微纤化共混物的非等这结晶特性,为了比较,同时考察了纯PE和PET/PE通常共混物的结晶特性。结果表明,PET微纤对PE有良好结晶异相成核作用,可提高结晶温度、缩短结晶时间、增大结晶速率,但使PE的结晶度和熔点降低;增加降温速率,结晶峰变宽且向低温方向移动。     

甲基丙烯酸甲酯-丁二烯-苯乙烯共聚物对刚性有机粒子增强聚碳酸酯共混物的增容作用EI北大核心CSCD

基于刚性有机粒子苯乙烯-丙烯腈共聚物(SAN)高强高模的特性,通过熔融共混法制备了聚碳酸酯(PC)/SAN/甲基丙烯酸甲酯-丁二烯-苯乙烯共聚物(MBS)的共混物,研究了MBS对共混物相形态和力学性能的影响。结果表明,MBS趋向于分布在PC与SAN的相界面处,增强了SAN粒子与PC基体之间的互相作用,使得SAN作为刚性有机粒子能更好地发挥增强增韧的效应。添加质量分数8%的MBS能使PC/SAN(75/25)共混物的拉伸强度、弹性模量、断裂伸长率和冲击强度分别提升4%,11%,62%和216%。而当MBS过量时(>16%),界面处的MBS胶束趋向于饱和,过量的MBS粒子出现在SAN相内部,使得PC/SAN(75/25)/MBS16中的SAN相尺寸有所增大,而具有较大SAN粒子尺寸的共混物表现出相对较低的断裂伸长率。     

热致液晶共聚酯原位复合材料相容性的研究

通过加入液晶聚酯酰胺和聚碳酸酯的多嵌段共聚物, 可以有效地降低基体聚碳酸酯的玻 璃化转变温度, 提高热致液晶高分子PET/60PHB 与聚碳酸酯原位复合材料的相容性。随嵌段共 聚物含量的增加, 共混物拉伸强度有所提高, 拉伸模量提高了15% , 同时, 冲击强度也得到了增长。 通过扫描电镜(SEM ) 的观察发现, 嵌段共聚物的加入改进了共混体系中两相间界面粘合, 促进了 液晶高分子分散相的变形。      

不同加工方法对乙烯-辛烯共聚物/聚乳酸共混物相结构与性能的影响

采用普通共混方法及原位微纤技术制备了乙烯-辛烯共聚物(POE)/聚乳酸(PLA)共混物,通过扫描电镜、力学性能测试和动态流变性能测试对材料形貌及性能进行表征。结果表明,对于POE/PLA普通共混物,PLA以球形颗粒分布在POE基体中,材料的拉伸应力-应变曲线无明显的屈服行为,PLA质量分数为20%时,材料拉伸强度为6.6 MPa; PLA的加入提高了材料的储能模量(G′)和损耗模量(G″)。对于POE/PLA微纤共混物,PLA在POE中形成了PLA微纤,当微纤的质量分数为10%时,材料的拉伸应力应变呈现双屈服行为,随微纤含量增加双屈服行为更明显。POE-20试样在应变为23%发生第1次屈服,在应变为240%发生第2次屈服,材料拉伸强度为8.8 MPa,其拉伸强度比相同PLA含量的普通共混物高33.3%,G′在低频区出现1个平台。     

离聚物Surlyn对聚对苯二甲酸乙二醇酯/聚萘二甲酸乙二醇酯共混物结晶性能和力学性能的影响

利用差示扫描热法(DSC)和偏光显微镜(POM)研究了乙烯-甲基丙烯酸离子键聚合物Surlyn对聚对苯二甲酸乙二醇酯(PET)/聚萘二甲酸乙二醇酯(PEN)共混物的结晶性能和力学性能的影响。研究结果表明,Surlyn对PET/PEN共混物具有化学成核作用。适量添加Surlyn,能促进PET/PEN共混物的成核结晶,明显提高结晶速度、结晶温度和结晶度,减小球晶尺寸,提高球晶均匀性,并有助于改善PET和PEN相容性,从而提高PET/PEN共混材料的拉伸强度、弯曲强度、弯曲模量和缺口冲击强度等力学性能。本研究体系Surlyn的最佳用量为2 phr。     

热拉伸比对PET/ PE 原位微纤化复合材料形态和拉伸性能的影响

采用熔融挤出2热拉伸2淬冷方法制备了聚对苯二甲酸乙二醇酯( PET) / 聚乙烯( PE) 原位微纤化复合材料。固定体系组成( PET/ PE 为15/ 85), 热拉伸比增加, PET 粒子相继从球状转变成椭球状、棒状和纤维状; 除了最小粒径保持基本不变外, 最大和平均粒径均逐渐减小。微纤化复合材料在PE 的加工温度下成型时, 纤维能够良好地保持在体系中, 但在PET 的加工温度下成型时, 纤维重新熔融, 形成球状粒子。复合材料的拉伸模量和拉伸强度随拉伸比增加显著增加, 表明微纤化对材料具有良好的增强效果; 而断裂伸长率随热拉伸比增加剧烈下降, 产生明显的韧-脆转变。比基本断裂功( we ) 先随热拉伸比( HSR) 增加而增加, 热拉伸比为19117 左右时达到最大值, 继续增加热拉伸比, we 降低。      

Morphology-tensile behavior relationship in injection molded poly(ethylene terephthalate)/polyethylene and polycarbonate/polyethylene blends (II) Part II Tensile behavior

The tensile behavior of injection molded poly(ethylene terephthalate) (PET)/polyethylene (PE) and polycarbonate (PC)/PE blends was investigated. For the same blend, due to the difference in the elongated dispersed particle concentration, the specimens molded at higher injection speed had slightly higher tensile strength and modulus than those molded at lower speed. Moreover, the reinforcement effect of PC to PE matrix was more noticeable than PET to PE. For the stress-strain behavior, while the PET/PE blend behaved like a common injection-molded immiscible blend the PC/PE blend unusually underwent twice yielding regardless of the cross head speed. For the PET/PE blend, obvious debonding between the dispersed PET particles and the matrix PE occurred upon elongation, resulting in large grooves and voids behind the particles. The PET particles experienced slight plastic deformation from spheres to ellipsoids. The stress whitening first appeared in the necking zone then extended along cold drawing zone. For the PC/PE blend, the PC particles in the core layer experienced considerable plastic deformation throughout the tensile test. Consequently, most of PC particles in the fractured specimen were deformed into fibers. Owing to comparatively high amount of injection-induced fibers that distributed or transferred the external stress, the specimen of PC/PE blend first deformed evenly in the entire tested zone, characterized by stress whitening in the entire specimen. Then after the first yielding, the stress decreased slowly while the elongation continued. When the elongation reached a certain point, the fibers in the sub-skin layer could no longer endure the external stress, and accordingly the second yield took place. Additionally, the fibrillation of the spherical PC particles in the core layer appeared right after the second yielding point.     

Morphology-tensile behavior relationship in injection molded poly(ethylene terephthalate)/polyethylene and polycarbonate/polyethylene blends (I) Part I Skin-core Structure

The skin-core structure of injection molded poly(ethylene terephthalate) (PET)/polyethylene (PE) and polycarbonate (PC)/PE blends was investigated. The results indicate that both shape and size of the PET and PC phases depended not only on the nature properties of PET/PE and PC/PE blends, but also on the injection molding parameters such as injection speed and the positions in the molded bars. The morphology in the section perpendicular to the melt flow direction included four layers, surface, sub-skin, intermediate layers as well as core zone. The surface layer was ignored in the present study. The sub-skin layer contained more or less fibrous structure and its thickness gradually decreased along the molded bar from the gate toward the non-gate end. At the same injection speed, the concentration of the injection-induced fibers in PC/PE blend was much higher than that in PET/PE blend. In the core region, the dispersed phase was mainly composed of spherical particles whose diameter increased along the melt flow pathway. Between these two layers, there was an intermediate layer where the dispersed particles mainly assumed the form of fibers, ellipsoids or spheres. Generally, no matter whether the dispersed particles were elongated or not during injection molding, the PET particles were larger than PC ones.     

Morphology and properties of ASA/PET blends

This study examines the morphology and mechanical properties of acrylate styrene acrylonitrile (ASA) and polyethylene terephthalate (PET) blends. The morphology of the 60/40 and 40/60 ASA/PET blends reveals a dispersed phase morphology verging on co-continuity, whilst the 50/50 blend appears to be completely co-continuous. Processing temperature has no effect on blend modulus or tensile strength and there is no statistically significant difference in mechanical performance between the three blend ratios. Charpy impact resistance decreases with increasing processing temperature. The fracture surface reveals a similar mushroom fibril morphology found for the ASA/polybutylene terephthalate (PBT) system, but is less extensive. Thermal analysis shows a marked drop in glass transition temperature for the blends compared to the component polymers.     

聚碳酸酯/聚乙烯相容性的研究

考察了聚碳酸酯与聚乙烯（ＰＣ／ＰＥ）及聚碳酸酯与马来酸酐接枝聚乙烯（ＰＣ／ＰＥ－ｇ－ＭＡＨ）共混体系的力学性能,研究了共混体系的相容性,研究表明,ＰＥ的加入有效地提高了ＰＣ的抗冲击性能,而ＰＣ／ＰＥ－ｇ－ＭＡＨ体系的力学性能及混溶性优于ＰＣ／ＰＥ体系。红外光谱表明,接枝ＰＥ与ＰＣ共混时,发生酯交换反应,冲击断口及样条截面的扫描电镜发现,ＰＣ／ＰＥ－ｇ－ＭＡＨ的相态分布均匀,两相之间存在一定的相互作     

Essential work of fracture testing of PC-rich PET/PC blends with and without transesterification catalysts

0.7 mm sheets of blends of polycarbonate (PC) with polyethylene terephthalate (PET) rich in PC in the presence and absence of three different transesterification catalysts have been obtained using reactive extrusion-calendering processing method in order to evaluate the fracture toughness of these materials applying the essential work of fracture (EWF) approach which has not been previously reported in the literature. The morphology has been characterized by scanning electron microscopy (SEM). In addition, the tensile properties of these materials were determined. There is a decrease on the essential term (w _e) values of PC/PET blends without transesterification catalysts while blends with transesterification catalysts present an increment in comparison with neat PC which may related to the product of the transesterification that plays like an emulsifier/compatibilizing agent to reduce the interfacial tension between the components of the blend and reduce the interfacial tension between the two immiscible or incompatible component phases to get a better fracture behavior. This is confirmed by the tensile test results obtained which demonstrate higher values for E and σ _y in the case of blends with transesterification catalysts compared with neat PC. For non-essential term of fracture (βw _p), blends without catalysts exhibit an increase compared with neat PC by increasing the amount of PET which may due to the lowering of the yielding stress. In contrary, the presence of transesterification catalysts and especially Zn-based shows decrease as a consequence of the restriction that occurred on the movement of PC segments during the transesterification reactions or as a decohesion of the dispersed phase during the test.     

Processing conditions, morphology and properties of a polycarbonate + a thermotropic polymer liquid crystal blend

We have investigated phase structure – properties relationships of polycarbonate (PC) + a polymer liquid crystal (PLC) blends processed in a twin-screw extruder at several conditions. The PLC is PET/0.82 PHB – a copolyester of poly(ethylene terephtalate) and p -hydroxybenzoic acid. For comparison the blend was additionally extruded in a wide range of shear rates in a capillary rheometer at two different spinning rates and compression-molded. The blend processed in the rheometer exhibits lower values of modulus and tensile strength than the blend extruded due to destruction of the initial orientation and dispersion level gained during extrusion. The orientation of PLC-rich islands increases up to the shear rate of 50–100 s^–1, whereas deformation at higher shear rates exhibits a droplet–breakup phenomenon, confirmed by SEM micrographs. The rheological measurements (oscillation mode) evidence a high shear thinning of the PLC. By contrast, the influence of the deformation rate on the viscosity for PC and the blend is negligible, suggesting also a low interaction level in the interfacial area. This conclusion was confirmed by dynamic mechanical measurements. As expected, our experiments prove that structure and properties of the blend are affected by processing (shear and elongation) conditions. Increasing shear rate leads to elongation of dispersed domains but exceeding critical values can lead to droplet breakup and destruction of created structure. The unique morphology created during extrusion can be destroyed during additional processing (in rheometer). Formation of fibrils is also dependent on additional treatment – spinning speed. Optimized spinning speed can lead to 50% increase in stiffness of the blend. Electronic Publication     

Influence of polymer type, composition, and interface on the structural and mechanical properties of core/sheath type bicomponent nonwoven fibers

In this study, we investigated the effect of polymer type, composition, and interface on the structural and mechanical properties of core–sheath type bicomponent nonwoven fibers. These fibers were produced using poly(ethylene terephthalate)/polyethylene (PET/PE), polyamide 6/polyethylene (PA6/PE), polyamide 6/polypropylene (PA6/PP), polypropylene/polyethylene (PP/PE) polymer configurations at varying compositions. The crystallinity, crystalline structure, and thermal behavior of each component in bicomponent fibers were studied and compared with their homocomponent counterparts. We found that the fiber structure of the core component was enhanced in PET/PE, PA6/PE, and PA6/PP whereas that of the sheath component was degraded in all polymer combinations compared to corresponding single component fibers. The degrees of these changes were also shown to be composition dependent. These results were attributed to the mutual interaction between two components and its effect on the thermal and stress histories experienced by polymers during bicomponent fiber spinning. For the interface study, the polymer–polymer compatibility and the interfacial adhesion for the laminates of corresponding polymeric films were determined. It was shown that PP/PE was the most compatible polymer pairing with the highest interfacial adhesion value. On the other hand, PET/PE was found to be the most incompatible polymer pairings followed by PA6/PP and PA6/PE. Accordingly, the tensile strength values of the bicomponent fibers deviated from the theoretically estimated values depending on core–sheath compatibility. Thus, while PP/PE yielded a higher tensile strength value than estimated, other polymer combinations showed lower values in accordance with their degree of incompatibility and interfacial adhesion. These results unveiled the direct relation between interface and tensile response of the bicomponent fiber.     

PE—MA对PE／CaCO3增容作用的研究

本文通过加入接枝马来酸酐的聚乙烯(PE-MA),促进非报性的聚乙烯分子和带有极性表面的填料之间的互容。用扫描电子显微镜观察共混物低温脆断面上碳酸钙的分布表明,在加有增容剂PE-MA的PE/CaCO_3共混物中,CaCO_3颗粒大小均匀且分布也均匀,PE-MA明显起到了增容作用。综合结果指出,PE-MA的加入量占PE/CaCO_3/PE-MA总重量的5～10％时增容效果较好。力学性能测试表明,随PE-MA用量的增加,共混物的拉伸强度明显提高。断裂伸长率变化较小,熔融指数略有下降。