具有高界面压应力的高分子共混物Ⅰ.制备和拉伸性能

考察了高界面压应力对不相容聚对苯二甲酸乙二醇酯(PET)/聚乙烯(PE)和聚碳酸酯(PC)/PE共混物拉伸性能的影响.高界面压应力是共混物低温成型(PE的成型温度)时,分散相与基体从加工温度冷却到室温过程中基体的收缩比分散相粒子大产生的.尽管PET/PE和PC/PE共混物极不相容,但拉伸强度和模量随着PET和PC含量增加而增加.PET与PC含量相同时,PC/PE的拉伸强度和模量高于PET/PE的.采用Takayanangi方程计算共混物的拉伸模量时,具有高界面压应力的PC/PE共混物的拉伸强度高于界面有良好粘结的共混物的理论值,表明在不添加增容剂时,可通过控制加工条件改善共混物界面相互作用,提高共混材料的性能.     

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。     

GEP/PO原位微纤化共混物的制备

利用“熔融挤出-热拉伸-淬冷”方法制备了几种通用工程塑料(GEP)／聚烯烃(PO)原位微纤化共混物，研究了加工设备(挤出机、注塑机、HAAKB流变仪附属单螺杆挤出机)和口模结构(窄缝状、片状、棒状)对聚对苯二甲酸乙二醇酯(PET)／聚乙烯(PE)共混物原位成纤的影响，发现带矩形窄缝状口模的挤出机挤出能产生更好的纤维结构，而有高剪切作用的对空注塑不能形成纤维结构。观察PET／PE，PET／聚丙烯(PP)，聚碳酸酯(PC)／PE及PC／PP共混物的成纤情况，发现通常认为不利于成纤(粘度比大于1)的PC／PE和PC／PP体系也形成了较好的纤维形态。总体上，PET／PE的成纤效果好于其它的体系。     

PET-MFIAA/ PP原位成纤复合材料的形态结构及力学性能

用钉挂预埋多功能界面活化剂(MFIAA)的PET(PET-MFIAA)与PP共混 - 挤出 - 拉伸,制备了PET-MFIAA/PP原位成纤复合材料,采用扫描电镜、偏光显微镜观察和力学性能测定的方法,研究了PET-MFIAA/PP的PET微纤形态、试样断面形态及力学性能,并与PET/PP、MFIAA/PET/PP两种原位成纤复合材料进行对比。结果表明: PET-MFIAA/PP PET微纤与PP基体间具有强的相互作用,PET微纤呈粗细不均匀、凹凸不平的异形形态及柔性界面等结构特征,形成了强的界面结合,其刚性、韧性均比纯 PP明显提高,含7.00% MFIAA的PET-MFIAA/PP复合材料的拉伸屈服应力、弯曲弹性模量和悬臂梁缺口冲击强度分别达到了纯PP的1.04倍、1.23倍和1.79倍。     

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。      

微型注塑对聚乳酸/聚丁二酸丁二醇酯共混物的形貌结晶和力学性能的影响

以聚丁二酸丁二醇酯(PBS)为分散相,聚乳酸(PLA)为基体树脂制备了PLA/PBS共混物,实现其微型注塑。结合流变行为和ANSYS Polyflow计算机模拟研究了微型注塑条件(包括熔体温度和注射速率)对PLA/PBS共混物结构和性能的影响。结果表明,微型注塑过程中强的剪切和拉伸应力场实现了PBS在PLA基体中的原位成纤,微型注塑条件对PBS分散相纤维形貌、基体树脂PLA结晶行为以及共混物力学性能有重要影响。发现提高熔体温度有利于增强壁面滑移效应,降低浇口区域的负拉伸作用,改善熔体流场的稳定性,从而有利于分散相PBS的原位成纤,然而过高的注射速率会因强负拉伸作用而破坏纤维结构,不利于PBS的原位成纤和共混物力学性能的改善。PBS原位成纤及其诱导PLA形成的取向结晶结构有利于共混物力学性能的改善。     

导电原位微纤化复合材料的有机液体响应特性

通过熔融预混合-高温挤出热拉伸-淬冷-低温成型方法制备导电原位微纤化CB/PET/PE材料,CB选择性分布在PET微纤中,微纤相互搭接形成导电网络。将试样浸入二甲苯溶液测试其电性能对有机液体的敏感性,结果表明,原位微纤化CB/PET/PE材料的电阻率迅速升高,相对于普通CB/PE导电复合材料有更高的响应强度,这是由其特殊的微观结构和形态决定的;另外,材料电阻率的变化与其厚度相关,当试样厚度由140μm增加至500μm时,材料的电阻率对二甲苯的敏感程度降低。     

液晶嵌段共聚物对PC/TLCP共混体系相容作用的研究

利用热致液晶高分子(TLCP)PET/60PHB与聚碳酸酯(PC)的多嵌段共聚物作为相容剂,研究了PC与该TLCP共混体系的力学性能、热性能、形貌及织构.研究表明,PC/TLCP二元共混物的相容性很差,TLCP在加工条件下不能形成分散于基体中的具有一定长径比的微纤,得到材料的力学性能较PC基体有所下降.相容剂的加入明显的改进了体系的相容性,表现在三元共混物的力学性能提高、微观TLCP粒子的直径变小,两相界面模糊.     

PET与PE混合物的回收——原位微纤化方法及其性能研究

研究了原位微纤化方法在回收聚对苯二甲酸乙二醇酯(PET)和高密度聚乙烯(HDPE)混合物方面的应用。本文通过四次挤出模拟塑料制品在环境中遇到的热氧作用和多次回收过程,研究了原位微纤化PET/HDPE共混物以及普通PET/HDPE共混物的性能变化。结果表明,随着挤出次数的增加,PET/HDPE普通共混物的拉伸性能和加工性能均下降,而PET/HDPE原位微纤化共混物的屈服强度得到了较大提高,同时模量也得到一定的提高。     

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。     

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.     

用SEM观察PE/PC共混物在拉伸和冲击作用前后的形态

介绍了典型的极不相容共混物（ＥＩＢ）聚乙烯／聚碳酸酯（ＰＥ／ＰＣ）体系的形态受组成的影响,以及共混物在受到拉伸前后,冲击前后的形态。通过扫描电子显微镜（ＳＥＭ）观察发现,组成不仅影响分散相粒子的大小,形状,还决定分散相与连续相的转变,共混物在受到拉应力（拉伸）和剪切应力（冲击）后,前者较多球状粒子变形成为有利于提高拉伸性能的纤维状,后者粒子和基体都发生了能提高抗冲击韧性的塑性变形。     

PET/PC共混物配比对其高压结晶行为的影响

利用SEM及W AXD等测试手段研究了配比对PET/PC共混物高压结晶行为的影响。SEM观察表明,随PC比例的增加,共混物高压下主要结晶形态以伸直链晶体,生长成熟的立体开放球晶,大尺寸球晶的方式变化。拟合分峰法和W arren-A verbach傅氏分析法的计算结果表明,随PC含量的增加,高压结晶共混物的结晶度降低,PET的平均晶粒尺寸总体呈减小趋势,晶粒尺寸分布则变窄,而晶格畸变平均值在一定PC比例范围内达到极大值。     

PC/PE共混体系在双螺杆挤出初期的形态演变EI

研究了聚碳酸酯/聚乙烯(PC/PE)共混物在双螺杆挤出初期过程中的形态演变规律。用扫描电子显微镜(SEM)观察螺杆轴向不同位置的共混物分散相形态,分析了混合初期PC分散相形态的演变规律;建立了PC分散相在软化变形条件下,由颗粒状变化为片状、纤维状结构并最终破碎松弛为球形粒子的模型。讨论了混合初期螺杆构型对PC分散相形态的影响,发现增加捏合块数量能降低混合初期分散相的平均粒径及其分布。     

PC/PET/PE-g-MAH三元共混物的研究

用ＤＳＣ、ＰＬＭ和ＳＥＭ研究了ＰＥｇＭＡＨ对ＰＣ／ＰＥＴ共混体系的相容性、结晶性、结晶形态及相形态的影响。结果表明,ＰＥｇＭＡＨ可以改善体系的相容性,提高ＰＥＴ的结晶能力和速率,改善ＰＣ、ＰＥＴ间的相互分布,且随含量的增加而程度加深。     

Thermomechanical properties of a polymer blend: Investigation of a third phase

This paper deals with immiscible blends of poly(ethylene terephthalate) with polycarbonate obtained by melt mixing. Miscibility of the polyester blends is influenced by transesterification reactions, that are catalyzed either by catalyst residues in the polyesters or by catalysts added on purpose in the blend. These reactions convert the initial homopolymers into block and even random copolymers and affect both the miscibility of the system and the adhesion between the phases. The effect of catalysts and stabilizers on the morphology of PET/PC 50/50 blends was investigated using dynamic mechanical thermal analysis, rheology, microscopy and tensile tests. PET/PC 50/50 containing 0.05 wt.% of lanthanide acetyl acetonate exhibit a irreversible transition occurring at temperature higher than the glass transitions of PET and PC. This transition induces a large increase of the shear modulus and it was attributed to the formation of a third phase in the blend.     

Fibrillar polymer–polymer composites: morphology, properties and applications

Micro- or nano-fibrillar composites (MFCs or NFCs) are created by blending two homopolymers (virgin or recycled) with different melting temperatures such as polyethylene (PE) and poly(ethylene terephthalate) (PET), and processing the blend under certain thermo-mechanical conditions to create in situ fibrils of the polymer that has the higher-melting temperature. These resulting fibrillar composites have been reported to possess excellent mechanical properties and can have wide ranging applications with suitable processing under controlled conditions. However, the properties and applications very much depend on the morphology of created polymer fibrils and their thermal stability. The present paper develops an understanding of the mechanism of micro-/nano-fibril formation in PE/PET and polypropylene (PP)/PET blends by studying their morphology at various stages of extrusion and drawing. It is revealed that this subsequent mechanical processing stretches the polymer chains and creates fibrils of very high aspect ratios, thus resulting in superior mechanical performance of the composites compared to the raw blends. The study also identifies the primary mechanical properties of the main types of MFCs, as well as quantifying their enhanced resistance to oxygen permeability. Furthermore, the failure phenomena of these composites are studied via application of the modified Tsai–Hill criterion. In addition to their usage as input materials in different manufacturing processes, possible applications of these fibrillar composites in two different areas are also discussed, namely food packaging with controlled oxygen barrier properties and biomedical tissue scaffolding. Results indicate a significant scope for using these materials in both areas.     

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.