嵌段共聚物相容剂对聚合物共混体系力学性能影响的连续介观模拟

结合介观动力学方法和三维弹簧格子模型, 研究了嵌段共聚物相容剂对相容性较差的聚合物二元共混体系力学性能的影响. 在适当范围内不断增加嵌段共聚物相容剂的用量, 研究了相容剂含量对体系杨氏模数及拉伸强度的影响, 同时也对不同体系材料的破碎位点进行了分析. 结果表明, 未加入相容剂的二元共混体系在拉伸模拟中表现出较低的拉伸强度, 而适量添加相容剂可以显著提升材料的拉伸强度, 随着相容剂含量的增加, 共混体系的破碎位点会发生转移并最终改善材料的整体性能. 而相容剂的加入对体系杨氏模数的影响较小. 该连续模拟方法为关联聚合物复合体系的微观结构和宏观力学性能提供了一条高效的途径.     

相容剂对PP/POE共混体系脆韧转变行为的影响

采用熔融挤出法制备了不同相容剂含量的PP/POE共混体系,测试了不同体系的脆韧转变温度、热性能和力学性能.结果表明,乙烯-丙烯多嵌段共聚物相容剂的加入降低了PP/POE共混物的脆韧转变温度,提高了共混物的韧性.AFM和STEM照片显示相容剂的加入减小了橡胶分散相的临界粒子间距,PP和POE在两相界面结合处相互扩散或渗透,实现了POE弹性体在PP树脂中合适的尺度分布以及良好的形态分散.当相容剂含量达到10％时,POE分散相尺寸细小均匀,分散相粒子粒径为0.54μm,粒子间距为0.1 μm,PP结晶链段更多地插入到弹性体内部,弹性体POE分散相形成明显的“硬核-软壳”结构.DSC曲线中结晶峰和熔融峰的变化说明适量的相容剂对于材料结晶度的提高具有一定的促进作用.力学性能测试结果可以看出相容剂的加入在提高材料韧性,降低其脆韧转变温度的同时也保持了材料的刚性性能.     

嵌段共聚物增容剂对不相容均聚物共混体系相行为和界面性质的影响

聚合物共混体系(又称聚合物合金)兼具其相应组分的均聚物和共聚物的多种特征,甚至具有新的理想性能,从而成为了一种具有极高经济价值的新材料.该材料的研发极大地丰富了高分子物理学、高分子化学和材料学的研究内容,拓宽了聚合物材料在现代工业中的应用,同时把聚合物材料研究推向了交叉科学的前沿.均聚物/嵌段共聚物/均聚物体系作为经典的三元聚合物共混体系,对其进行深入地研究,不仅可以促进人们对高分子科学中重要问题的理解,而且可为新型嵌段共聚物增容剂的改良和设计提供理论依据.近年来,有关聚合物共混体系的实验、理论和计算机模拟工作很多,并且取得了较大的进展,但是相关综述较少.本文以均聚物/嵌段共聚物/均聚物体系为例,综述该领域的基本概念和发展历史,并着重介绍两嵌段共聚物增容剂对该三元共混体系相行为和界面性质的影响.此外,还介绍了这一领域的关键科学问题、发展前景和研究方向.     

三元聚合物共混体系的微观结构与力学性能模拟

建立一种构型模拟与力学性能模拟相结合的连续模拟方法研究了三元共混物(两种均聚物与一种共聚物)中交替共聚结构与嵌段共聚结构对力学性能的影响。通过蒙特卡罗模拟获得其构型,然后将该构型作为弹簧格子模型的数据输入,模拟三元共混体系的微观结构与力学性能。模拟结果表明:交替共聚物在体系中更倾向于在两种均聚物的界面处自我缠绕,而嵌段共聚物的两端分别渗透进与之相容的均聚物体相中;三元共混物的力学性能与其内部的两相界面结构相关;应变在交替共聚物体系中均匀分布,导致更多的断裂发生在体相中,交替共聚物体系比嵌段共聚物体系力学性能更强且更具韧性。这种连续模拟方法为研究材料组成与力学性能之间的关系提供了一种新方案。     

热致液晶／PEEK／嵌段共聚物共混体系的结构与性能

用ＷＡＸＤ、ＳＥＭ及力学性能测试等研究热致液晶／ＰＥＥＫ／嵌段共聚物三元共混体系形态、结构和性能。结果表明嵌段共聚物的加入，使体系具有一定的相容性和较好的界面粘接，共混物的强度、模量有一定的提高，对共混物的结晶行为具有明显的影响，当热致液晶含量高时，基材与液晶两相间出现明显的分离现象，即“皮－芯”结构．     

均聚物/两嵌段共聚物/均聚物三元聚合物共混体系界面性质的Monte Carlo模拟

利用格子Monte Carlo(MC)模拟方法研究了两嵌段共聚物增容剂AB的链长及浓度对不相容性均聚物A/B共混体系界面性质的影响.研究结果表明,当两嵌段共聚物的体积分数φC=0.05时,随着两嵌段共聚物分子链长NC从10增至20,界面厚度剧烈减小,而当两嵌段共聚物的分子链长NC进一步增加到60时,界面厚度轻微增加;两嵌段共聚物的取向参数q随着分子链长的增长而增加,即共聚物分子在垂直界面方向的拉伸程度增大.当两嵌段共聚物AB的分子链长NC固定为10时,随着链浓度增大,界面厚度增加,共聚物分子链取向参数q减小,共聚物分子在垂直界面方向的拉伸程度减小.     

共聚物在聚合物共混体系中的增容作用I.嵌段共聚物

随着高分子合金领域的研究发展，以共聚物作为增容剂对不相容的聚合物共混体系进行改性已得到了广泛的研究和应用。本文分为两篇，分别介绍利用嵌段共聚物、接枝共聚物和无规共聚物所做的增容改性研究。本篇着重讨论嵌段共聚物(包括两嵌段和三嵌段以及多嵌段共聚物)在聚合物共混体系中的增容作用和增容机理。     

含有机硅多嵌段及其接枝共聚物的表面组成

利用ＸＰＳ对聚二甲基硅氧烷与聚砜或／和聚对羟基苯乙烯组成的二元和三元多嵌段和接枝共聚物及其共混物进行了研究。结果表明溶液成果的聚合物样品的表面都存在有机硅富集，共混物的表面富集程度等于接枝共聚物，更高于多嵌段共聚物，讨论了有机硅含量和键接结构对有机硅表面富集的影响。     

iPS—b—iPP共聚物对iPS／iPP共混物的性能和形态影响的研究

报道了苯乙烯－丙烯等规嵌段共聚物增溶作用及ｉＰＳ－ｂ－ｉＰＰ／ｉＰＳ／ｉＰＰ三组分共混体系微观形态和力学性能的研究结果。ｉＰＳ－ｂ－ｉＰＰ的加入明显地改善了ｉＰＳ／ｉＰＰ二组分共混物的力学性能；共聚物含量超过１５％时，三组分共混物的抗冲击强度超过ＨＩＰＳ的抗冲击强度，并具有较高的耐热性。ＳＥＭ结果表明，ｉＰＳ－ｂ－ｉＰＰ在ｉＰＳ／ｉＰＰ共混中起到了相分散和相间“偶联”作用，并降低了共混体系的微相尺     

高密度聚乙烯共混调控烯烃嵌段共聚物拉伸性能

通过熔融共混法制备了高密度聚乙烯(HDPE)与烯烃嵌段共聚物(OBC)的共混物,研究了HDPE含量对共混体系结晶和拉伸行为的影响.实验结果表明,共混物熔体存在相分离.结晶时两组分互相影响,出现共结晶现象.共混物具有优异弹性回复与高断裂伸长率,而拉伸模量与断裂强度随着HDPE含量增加而逐渐增大.借助Slip-link橡胶弹性理论对应力应变曲线进行了分析,发现拉伸曲线可以很好的用理论模型进行拟合.将共混物的微观结构变化同模型参数进行了对比,建立了共混物结构和性能的有效关联.     

酞侧基聚芳醚砜／对苯二甲酸乙二酯－对羟基苯甲酸嵌段共聚物共混物的研究

酞侧基聚芳醚砜／对苯二甲酸乙二酯－对羟基苯甲酸嵌段共聚物共混物的研究李刚，殷敬华，李滨耀（中国科学院长春应用化学研究所，长春，１３００２２）关键词酞侧基聚芳醚砜，热致性液晶高聚物，原位复合材料，对苯二甲酸乙二酯－对羟基苯甲酸嵌段共聚物将热塑性树脂与热...     

酞侧基聚芳醚砜／对苯二甲酸乙二酯－对羟基苯甲酸嵌段共聚物共混物的研究

The blends of phenolphthalein Polyethersulfone (PES - C ) and a thermotropic liquid crystalline polymer (LCP ) were prepared using melting mixing method.Rheological and mechanical properties of the blends were investigated. It was shown that addition of LCP in PES-C resulted in marked reduction of melt viscosity and improved processibility. The Chadly impact strength of the blend containing 2. 5% LCP increased about 2. 5 times comparing with pure PES-C. The tensile strength, Young's modulus, fie-cural strength and flexural modulus of the PES-C/LCP blends were also improved on some extent. The morphology of these blends were also observed by SEM,and the relationship between the me-chanical properties and the morphology of blends were discussed.     

Reactive compatibilization of nylon copolymer/EPDM blends: experimental aspects and their comparison with theory

In situ reactive compatibilization was first time applied to a low melting nylon (nylon 6 and 66 copolymer) and EPDM blend system. The effects of in situ compatibilization and concentration of compatibilizer on the morphology and mechanical properties of nylon/EPDM blends have been investigated. The influence of EPM‐g‐MA on the phase morphology was examined by the scanning electron microscopy (SEM) after preferential extraction of the minor phase. The SEM micrographs were quantitatively analyzed for domain size measurements. The compatibilizer concentrations used were 0, 1, 2.5, 5, and 10 wt%. The graft copolymer (nylon‐g‐EPM) formed at the interface showed relatively high emulsifying activity. A maximum phase size reduction was observed when 2.5 wt% of compatibilizer was added to the blend system. This was followed by a leveling‐off at higher loadings indicating interfacial saturation. The conformation of the compatibilizer at the interface was deduced based on the area occupied by the compatibilizer at the blend interface. The experimental compatibilization results were compared with theoretical predictions of Noolandi and Hong. It was concluded that the molecular state of compatibilizer at interface changes with concentration. The in situ compatibilized blends showed considerable improvement in mechanical properties. Measurement of tensile properties shows increased elongation as well as enhanced modulus and strength up on compatibilization. At higher concentrations of compatibilizer, a leveling‐off of the tensile properties was observed. A good correlation has been observed between the mechanical properties and morphological parameters. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of the compatibilizer PE‐g‐GMA on the mechanical,thermal and morphological properties of virgin and reprocessed LDPE/corn starch blends

The effects of the compatibilizer polyethylene grafted with glycidyl methacrylate (PE‐g‐GMA) on the properties of low‐density polyethylene (LDPE) (virgin and reprocessed)/corn starch blends were studied. LDPE (virgin and reprocessed)/corn starch blends containing 30, 40 and 50 wt% starch, with or without compatibilizer, were prepared by extrusion and characterized by the melt flow index (MFI), tensile test, dynamic mechanical analysis (DMTA) and light microscopy. The addition of starch to LDPE reduced the MFI values, the tensile strength and the elongation at break, whereas the modulus increased. The decreases in the MFI and tensile properties were most evident when 40 and 50 wt% starch were added. Blends containing 3 wt% PE‐g‐GMA had higher tensile strength values and lower MFI values than blends without compatibilizer. Light microscopy showed that increasing the starch content resulted in a continuous phase of starch. Copyright © 2005 John Wiley & Sons, Ltd.     

Novel elastomeric polyurethane fibers modified with polypropylene microfibers

Extrusion of immiscible polymer biphasic blends to form in situ microfibers of the minor component in the matrix of the major component is an elegant way to create composites with new properties. The process was used to obtain thermoplastic polyurethane elastomers modified with polypropylene microfibers. The effect of phase interaction on blend morphology and properties was studied by running a series of blends with and without a maleated polypropylene compatibilizer. Six different blends were prepared: three with compatibilizer and three without the compatibilizer. All blends contained polypropylene as a minor component (80/20; 90/10 and 95/5). Extrusion spinning of polyurethane/polypropylene blends with and without compatibilizer resulted in polyurethane fibers modified with highly-oriented polypropylene microfibrils at all component ratios. Increasing polypropylene concentration in the thermoplastic polyurethane matrix increased hardness and modulus, but did not affect tensile strength and lowered elastic recovery.     

动态固化聚丙烯/环氧树脂共混物的研究

将动态硫化技术应用于热塑性树脂 热固性树脂体系 ,制备了动态固化聚丙烯 (PP) 环氧树脂共混物 .研究了动态固化PP 环氧树脂共混物中两组分的相容性、力学性能、热性能和动态力学性能 .实验结果表明 ,马来酸酐接枝的聚丙烯 (PP g MAH)作为PP和环氧树脂体系的增容剂 ,使分散相环氧树脂颗粒变细 ,增加了两组分的界面作用力 ,改善了共混物的力学性能 .与PP相比 ,动态固化PP 环氧树脂共混物具有较高的强度和模量 ,含 5 %环氧树脂的共混物拉伸强度和弯曲模量分别提高了 30 %和 5 0 % ,冲击强度增加了 15 % ,但断裂伸长率却明显降低 .继续增加环氧树脂的含量 ,共混物的拉伸强度和弯曲模量增加缓慢 ,冲击强度无明显变化 ,断裂伸长率进一步降低 .动态力学性能分析 (DMTA)表明动态固化PP 环氧树脂共混物是两相结构 ,具有较高的储能模量 (E′)     

Morphological,rheological, and mechanical properties of ethylene propylene diene monomer/carboxylated styrene-butadiene rubber/multiwall carbon nanotube nanocomposites

Abstract

A hybrid nanocomposite based on ethylene propylene diene monomer/carboxylated styrene-butadiene rubber (EPDM/XSBR) blend with different concentrations (0–7 phr) of multiwall carbon nanotube (MWCNT) was prepared on a two-roll mill. The role of grafted maleic anhydride (EPDM-g-MA) as compatibilizer and the effect of different concentrations of MWCNT on mechanical properties, morphology, rheological and curing characteristics of nanocomposites were investigated. The curing behavior of the prepared nanocomposites was studied using a rheometer. Also, the microstructure of nanocomposites was observed using TEM. By increasing the MWCNT concentration in the compatible blends, the curing time and scorch time of the blends decreased, while the maximum and minimum torque increased. Failure surface morphology studies showed that the existence of EPDM-g-MAH compatibilizer improved the distribution of MWCNT within the polymer matrix and uniform distribution of MWCNT with a small amount of aggregation was obtained. On the other hand, the presence of MWCNT in the matrix led to a sharper surface of the fracture. Also, mechanical properties such as modulus, tensile strength, hardness, fatigue, resilience and elongation-at-break for compatible EPDM/XSBR nanocomposite showed better results than those for incompatible composite.     

Nanomechanical and Chemical Mapping of the Structure and Interfacial Properties in Immiscible Ternary Polymer Systems

It is a challenge to identify each phase in a multi-component polymer system and uniquely determine the interfacial properties between the different phases. Using atomic force microscopy nanomechanical mapping(AFM-NM) and AFM-based infrared spectroscopy(AFMIR), we identify each phase, visualize structural developments, and determine the interfacial properties in a blend of three polymers: high-density polyethylene(HDPE), polyamide(PA6) and poly(styrene-b-ethylene-co-butylene-b-styrene)(SEBS). Each phase can be identified from the Young's modulus, along with the structural development within the phases before and after compatibilization. The interfacial widths between HDPE/PA6,HDPE/SEBS and SEBS/PA6 were determined independently in one measurement from a Young's modulus map. The structural, mechanical property development and identity of the phases were determined by AFM-NM, while AFM-IR, providing complementary chemical information,identified interfacial reactions, showed the chemical affinity of a compatibilizer with the component phases, and mapped the distribution of the compatibilizer in the ternary polymer blends. The chemical, structural and interfacial information obtained by these measurements provide information that is essential for producing mechanically robust materials from incompatible mixtures of polymers.     

Properties of immiscible and ethylene-butyl acrylate-glycidyl methacrylate terpolymer compatibilized poly (lactic acid) and polypropylene blends

Poly(lactic acid) (PLA) and polypropylene (PP) blends of various proportions were prepared by melt-compounding. The miscibility, phase morphology, thermal behavior, and mechanical and rheological properties of the blends were investigated. The blends were immiscible systems with two typical morphologies, spherical droplet and co-continuous, and could be obtained at various compositions. Complex viscosity, storage modulus and loss modulus depend on the PP content. Thermal degradation of all blends led to two weight losses, for PLA and PP. The incorporation of PP improved the thermal stability of the blend. The effect of compatibilizer (ethylene-butyl acrylate-glycidyl methacrylate terpolymer, EBA-GMA) on the morphology and mechanical properties of 70/30 w/w PLA/PP blends was investigated. The tensile strength of these blends reached a maximum for 2.5 wt% EBA-GMA, and impact strength increased with increasing EBA-GMA content, suggesting that EBA-GMA is an effective compatibilizer for PLA/PP blends.