St存在下MAH熔融接枝PP机理的探讨

在哈克转矩流变仪和双螺杆挤出机中,对苯乙烯（St）存在下马来酸酐（MAH）熔融接枝聚丙烯（PP）进行了研究.实验表明：St的加入不仅可显著提高MAH的接枝率,而且可减少PP的降解;当St和MAH的摩尔比为1时,MAH接枝率最大.通过反应机理分析得出：没有St时,MAH主要以单分子形式在PP降解之后接枝到PP上;而在St存在下,St与MAH以交替接枝的形式或者配合物（CTC）形式在PP降解之前接枝到PP上,形成St和MAH交替聚合的长链.后者使MAH的接枝率增加,同时增大了PP的交联,减小了PP的降解.     

应力引发官能化EPDM/HDPE及其对PA66/EPDM/HDPE 共混物相形态和力学性能的影响

通过提高双螺杆挤出机螺杆转速的方法,研究了熔融挤出过程中高剪切应力对马来酸酐(MAH)官能化三元乙丙橡胶(EPDM)与高密度聚乙烯(HDPE)共混物的接枝率、熔体流动速率及凝胶含量的影响.随着双螺杆挤出机螺杆转速的增加,强烈的机械剪切应力引发EPDM/HDPE共混物大分子链的断链反应形成大分子自由基,从而引发接枝反应制...     

大分子相容剂改性Mg(OH)2/PP阻燃材料的性能

用双螺杆挤出机熔融挤出法制备了相容剂改性氢氧化镁/聚丙烯[Mg(OH)2/PP]阻燃材料。研究了马来酸酐接枝聚丙烯(PP-g-MA),马来酸酐接枝(乙烯/辛烯)共聚物(POE-g-MA)和马来酸酐接枝聚醋酸乙烯酯(EVA-g-MA)3种大分子相容剂对阻燃材料的熔体流动性、结晶行为、力学性能和断口形态的影响。结果表明:相容剂PP-g-MA和POE-g-MA的加入使阻燃材料的熔体流动速率降低,PP结晶温度提高,EVA-g-MA的加入使阻燃材料熔体流动速率数提高;Mg(OH)2对PP结晶存在异相成核作用,Mg(OH)2的加入使PP的冲击强度、拉伸强度和断裂伸长率降低,杨氏模量提高;相容剂改性后Mg(OH)2/PP阻燃材料的拉伸强度提高,其中以PP-g-MA最为明显,而POE-g-MA则提高了阻燃材料的冲击强度。     

甲基丙烯酸缩水甘油酯/苯乙烯固相接枝聚丙烯

以苯乙烯(St)为共单体，过氧化苯甲酰(BPO)为引发剂，采用固相接枝反应将甲基丙烯酸缩水甘油酯(GMA)接枝到聚丙烯(PP)大分子链上。研究了反应时间、单体用量、引发剂用量等因素对接枝率的影响。采用凝胶渗透色谱(GPE)测定了PP和接枝物PP-g-(GMA-St)的分子量和分子量分布。结果 表明固相接枝PP反应条件为[GMA／[St]=2，反应3．5h，加入GMA 10份，BPO 5份。St的加入有助于GMA与PP的接枝，同时在一定程度上抑制了PP的降解。     

反应挤出接枝共聚反应表观链增长常数的测量

以预辐照的LLDPE反应挤出接枝MAA作为研究对象,通过在双螺杆挤出机中的不同部位取样,用FTIR分析接枝物及均聚物的产量,并用ESR测试链增长自由基浓度,设计了测定接枝和均聚反应初始阶段的表观链增长常数的方法.结果表明,在本实验测试范围内表观接枝链增长常数不同于均聚链增长常数;所得的测量值符合理论预测值,证明测试方法适合高温熔融体系的研究.     

多单体接枝聚丙烯对PBT/PP共混体系的形态结构及力学性能影响研究

研究了甲基丙烯酸缩水甘油酯 (GMA)和苯乙烯 (St)多单体熔融接枝聚丙烯 (PP g (GMA co St) )对聚对苯二甲酸丁二酯 (PBT) 聚丙烯 (PP)共混物的形态结构和力学性能的影响 .利用双螺杆挤出机对PBT PP合金进行共混挤出 ,使用DSC、FT IR和SEM、TEM等手段对共混物进行了分析和相形态观察 ,并测试了力学性能 .实验证明 ,熔融共混过程中PP g (GMA co St)的环氧基团可以与PBT的端羧基发生化学反应 ,就地生成了PBT g PP共聚物 ,该共聚物可对PBT PP合金起到良好的增容剂作用 ,使共混物的相区尺寸显著减小 ,共混物的拉伸强度和冲击强度等力学性能同时得到明显改善 ,达到了弹性体系或小分子增容所难以达到的力学性能平衡的效果 .此外 ,TEM的研究还在PBT PP g (GMA co St)共混物中发现了特殊的微相分离结构     

反应挤出接枝共聚反应表观链增长常数的测量

以预辐照的LLDPE反应挤出接枝MAA作为研究对象，通过在双螺杆挤出机中的不同部位取样，用FFIR分析接枝物及均聚物的产量，并用ESR测试链增长自由基浓度，设计了测定接枝和均聚反应初始阶段的表观链增长常数的方法,结果表明，在本实验测试范围内表观接枝链增长常数不同于均聚链增长常数；所得的测量值符合理论预测值，证明测试方法适合高温熔融体系的研究。     

双单体固相共聚改性聚丙烯技术及其机理研究

在马来酸酐(MAH)固相接枝改性聚丙烯(PP)的过程中加入合适比例的异氰脲酸三烯丙酯(TAIC)作为共聚单体,可以大大提高MAH在PP上的接枝率,同时可以有效抑制在普通固相接枝过程中PP的严重降解,得到了性能较好的高极性PP.与普通固相接枝法与熔体接枝法对比,双单体固相共聚接枝改性PP是一种得到高极性PP的有效方法.本文同时对双单体在固相接枝反应中的作用机理进行了探讨.     

马来酸酐-苯乙烯熔融接枝聚丙烯的影响因素及其性能研究

用单螺杆挤出机制备了马来酸酐 (MAH) 苯乙烯 (St)对聚丙烯 (PP)的多组分单体自由基熔融接枝体系 .研究证实了当两种单体物质的量比约为 1∶1时 ,接枝物的接枝率最高 ,而熔体流动速率 (MFR)最大 .对反应体系影响因素的研究表明单体用量和引发剂用量对不同单体用量比的系列接枝物的接枝率会产生不同的影响 ;另外 ,单体用量增加 ,接枝物的MFR减小 ,过氧化二异丙苯 (DCP)用量增加 ,接枝物的MFR增加 .对多单体熔融接枝聚丙烯PP g (MAH co St)的力学性能研究发现 ,选用合适的单体用量比、单体用量和DCP用量时 ,所制备的接枝物可具有与纯PP相当或更佳的力学性能     

马来酸酐化1,2-聚丁二烯熔融接枝聚丙烯木塑复合材料相容剂的研究

采用熔融接枝法,将马来酸酐化1,2-聚丁二烯(MAPB)在过氧化二异丙苯(DCP)的存在下接枝到聚丙烯(PP)上。使用傅里叶变换红外光谱(FTIR)、热重分析(TG)和差示扫描量热(DSC)法对接枝产物进行表征,将其作为木塑复合材料(WPCs)界面相容剂,以复合材料力学性能为指标对接枝工艺配方进行评价。结果表明:MAPB可以与PP发生接枝反应,并且MAPB的加入能够提高PP的结晶温度和热稳定性。当接枝反应温度为180℃,质量比m(MAPB)∶m(PP)∶m(DCP)=13∶37∶0.2时,所制得的接枝产物对木塑复合材料力学性能提高有最好的效果,以此来确定MAPB-g-PP的工艺配方。     

多官能团单体对马来酸酐接枝聚丙烯流变行为的影响

研究了多官能团辅助单体偏苯三酸三丙烯酯(TATM)对马来酸酐接枝聚丙烯的熔体流动速率(MFR)和流变行为的影响.当以不含抗氧剂的聚丙烯粉料为原料时,TATM的加入对稳定接枝产物MFR的效果并不理想.但将聚丙烯粉料添加抗氧剂并造粒后,TATM的加入则可有效稳定体系的MFR,各种流变曲线显示出接枝产物的熔体弹性明显提高,说明有枝化或交联结构出现.针对PP粉料和粒料间接枝产物流变行为存在的重大差异,结合熔体自由基接枝反应的机理进行了解释.TATM能够起到稳定MFR的效果是由于其提高了接枝物的熔体弹性,从而抵消了聚丙烯熔体接枝反应中所不可避免的β断链所造成的剪切黏度下降.聚丙烯粉料和粒料中抗氧剂的差异对聚丙烯的加工降解有严重影响,造成了TATM在不同聚丙烯体系中效果的差异.     

1,6-己二醇二丙烯酸酯和苯乙烯多单体熔融接枝制备长支链聚丙烯研究

采用哈克转矩流变仪制备了1,6-己二醇二丙烯酸酯(HDDA)和苯乙烯(St)多单体熔融接枝聚丙烯(PP)体系.红外测试结果表明St的加入能够促进HDDA接枝到PP主链,提高接枝率.动态流变行为研究结果也表明采用多单体熔融接枝PP更有利于体系在熔融接枝中生成长支链(LCB).随着St单体添加量的增加,HDDA的接枝率增大...     

Fracture studies of polypropylene/nanoclay composite. Part I: Effect of loading rates on essential work of fracture

Polypropylene (PP)/Montmorillonite (MMT) nanoclay based composite was prepared by melt compounding with maleic anhydride grafted polypropylene (MA-g-PP) as a compatibilizer in a twin-screw extruder, and the test specimens were injection molded. Mechanical properties such as tensile modulus, flexural modulus, yield strength and maximum percent strains were measured for pure PP and PP based nanocomposite to establish the effect of clay platelet reinforcement. The fracture properties were measured by using the essential work of fracture (EWF) method. PP/clay nanocomposite shows 25% improvement in specific EWF compared to pure PP. The variation of EWF parameters with loading rate is discussed, whilst the mechanisms of fracture are considered in a subsequent paper.     

RHEOLOGICAL BEHAVIOR OF KAOLIN TOUGHENED POLYPROPYLENE COMPOSITES

The relation between the rheological behavior and various interfacial properties ofKaolin rigid particle toughened polypropylene (PP / Kaolin) composites were studied bymeans of parallel-plate rheometer, melt flow rate apparatus, scanning electron microscopy(SEM) and other testing methods. The results show that addition of interfacial modffier toPP/Kaolin composites is advantageous to homogeneous dispersion of filler in PP matrix,formation of flexible interlayer between Kaolin particles and PP matrix and Amprovementof the melt processibility of the composites.     

Rheological,morphological and mechanical properties of flax fiber polypropylene composites: influence of compatibilizers

In this work, the rheological, mechanical and morphological properties of flax fiber polypropylene composites were investigated. The effect of incorporating a polypropylene grafted acrylic acid or a polypropylene grafted maleic anhydride on these properties has been studied as well. According to scanning electron microscopic observations and tensile tests, the addition of a compatibilizer improved the interfacial adhesion between the flax fibers and the polymer matrix. The tensile modulus of composite containing 30 wt% flax fibers was improved by 200 % and the tensile strength improved by 60 % in comparison with the neat PP. Plasticizing effect of the compatibilizers as a result of their lower melt flow index was also shown to decrease the rheological properties of the composites, even though the effect was not pronounced on the mechanical properties.     

Effect of Silane Coupling Agent and Compatibilizer on Properties of Short Rossells Fiber/Poly(propylene) Composites

Rossells fiber reinforced polypropylene composites were prepared by melt mixing. The fiber content was 20 wt%. Octadecyltrimethoxysilane (OTMS) and maleic anhydride grafted polypropylene (MAPP) were used to improve the adhesion between poly(propylene) (PP) and the fiber. The mechanical, rheological, and morphological properties, and heat distortion temperature (HDT) of the composites were investigated. Tensile strength, impact strength, flexural strength and HDT of MAPP modified PP composites increased with an increase in MAPP content. However, no remarkable effect of MAPP content on the Young's modulus of the composites was found. OTMS resulted in small decreases of tensile strength and Young's modulus, and increase in impact strength. Scanning electron micrographs revealed that MAPP enhanced surface adhesion between the fiber surface and PP matrix.     

提高聚丙烯熔体强度的研究进展

熔融状态下聚丙烯的熔体强度对其发泡效果有着举足轻重的作用,高熔体强度有利于聚丙烯的热成型,从而得到优质的发泡材料。本文综述了聚丙烯泡沫塑料的特点、性能及聚丙烯熔体强度较低对发泡过程的影响,分别从共混改性法、交联改性法、填充改性法这三种提高聚丙烯发泡性能的途径上对目前国内外致力于聚丙烯熔体强度的研究进展进行了重点介绍,指出聚丙烯化学交联改性与共混改性、共聚改性等方法并用乃是改善聚丙烯发泡性能的重点及热点。     

Microstructure and non-isothermal crystallization behavior of PP/PLA/clay hybrid nanocomposites

Journal of Thermal Analysis and Calorimetry - Various compositions of polypropylene (PP) and poly(lactic acid) (PLA) blends were prepared by one-step melt compounding in a twin-screw extruder. Two...     

Reactive melt blends of thermoplastic polyolefins,MAH‐g‐PP and nylon 6

Reactive melt blends of an ethylene‐propylene‐diene terpolymer (EPDM) based thermoplastic elastomer (TPE), maleic anhydride grafted polypropylene (MAH‐g‐PP), and nylon 6 were prepared in a single screw extruder and evaluated in terms of morphological, rheological, thermal, dynamic mechanical, and mechanical properties of the blends. It was found that MAH‐g‐PP‐co‐nylon 6 copolymers were in situ formed and acted as effective compatibilizers for polypropylene (PP) and nylon 6. Phase separation of PP and EPDM in TPE increased with the addition and increasing amount of MAH‐g‐PP and nylon 6, leading to decreased glass transition temperature (T_g) of TPE and increased crystalline melting temperature (T_m) of PP. Copyright © 2004 John Wiley & Sons, Ltd.