(PE-g-PB-g-PA6)接枝共聚物中PA6链段结晶行为研究

采用选择性溶剂交替抽提的方法提纯在PE-g-PB-g-MA/PA6共混物中原位生成的接枝共聚物PE-g-PB-g-PA6,通过TEM﹑XPS﹑XRD﹑DSC等方法研究了该接枝共聚物的形貌与结晶行为。结果表明,PA6链段的结晶受到相形貌和分子结构的限制,扩散速度降低,导致在通常的结晶速率条件下(10℃/min)结晶不完善。

Fractionated crystallization of dispersed PA6 phase of PP/PP-g-MAH/PA6 blends

Fractionated crystallization behavior of dispersed PA6 phase in PP/PA6 blends compatibilized with PP-g-MAH was investigated by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), polarized light microscopy (PLM), and wide-angle X-ray diffraction (WAXD) in this work. The lack of usual active heterogeneities in the dispersed droplet was the key factor for the fractionated crystallization of PA6. The crystals formed with less efficient nuclei might contain more defects in the crystal structures than those crystallized with the usual active nuclei. The lower the crystallization temperature, the lesser the perfection of the crystals and the lower crystallinity would be. The fractionated crystallization of PP droplets encapsulated by PA6 domains was also observed. The effect of existing PP-g-MAH-g-PA6 copolymer located at the interface on the fractionated crystallization could not be detected in this work.

Polyolefin based antibacterial membranes derived from PE/PEO blends compatibilized with amine terminated graphene oxide and maleated PE

In this study, various strategies like amine terminated GO (GO-NH2), in situ formed polyethylene grafted GO (PE-g-GO) and their combinations with maleated PE (maleic anhydride grafted PE) were adopted to reactively compatibilize blends of low density polyethylene (LDPE) and polyethylene oxide (PEO). These blends were further explored to design porous, antibacterial membranes for separation technology and the flux and the resistance across the membranes were studied systematically. It was observed that GO-NH2 led to uniform dispersion of PEO in a PE matrix and further resulted in a significant improvement in the mechanical properties of the blends when combined with maleated PE. The efficiency of various compatibilizers was further studied by monitoring the evolution of morphology as a function of the annealing time. It was observed that besides rendering uniform dispersion of PEO in PE and improving the mechanical properties, GO-NH2 further suppresses the coalescence in the blends. As the melt viscosities of the phases differ significantly, there is a gradient in the morphology as also manifested from scanning acoustic microscopy. Hence, the membranes were designed by systematically reducing the thickness of the as-pressed samples to expose the core as the active area for flux calculations. Selected membranes were also tested for their antibacterial properties by inoculating E. coli culture with the membranes and imaging at different time scales. This study opens new avenues to develop PE based cost effective anti-microbial membranes for water purification.

Polyolefin based antibacterial membranes derived from PE/PEO blends compatibilized with amine terminated graphene oxide and maleated PE

In this study, various strategies like amine terminated GO (GO-NH2), in situ formed polyethylene grafted GO (PE-g-GO) and their combinations with maleated PE (maleic anhydride grafted PE) were adopted to reactively compatibilize blends of low density polyethylene (LDPE) and polyethylene oxide (PEO). These blends were further explored to design porous, antibacterial membranes for separation technology and the flux and the resistance across the membranes were studied systematically. It was observed that GO-NH2 led to uniform dispersion of PEO in a PE matrix and further resulted in a significant improvement in the mechanical properties of the blends when combined with maleated PE. The efficiency of various compatibilizers was further studied by monitoring the evolution of morphology as a function of the annealing time. It was observed that besides rendering uniform dispersion of PEO in PE and improving the mechanical properties, GO-NH2 further suppresses the coalescence in the blends. As the melt viscosities of the phases differ significantly, there is a gradient in the morphology as also manifested from scanning acoustic microscopy. Hence, the membranes were designed by systematically reducing the thickness of the as-pressed samples to expose the core as the active area for flux calculations. Selected membranes were also tested for their antibacterial properties by inoculating E. coli culture with the membranes and imaging at different time scales. This study opens new avenues to develop PE based cost effective anti-microbial membranes for water purification.

低分子量马来酸酐化聚丁二烯橡胶改性聚乙烯增韧尼龙6

尼龙6是世界上使用最广泛的工程塑料之一，由于尼龙6大分子链中含有酰胺键能形成氢键，使其具有强韧、耐磨、耐冲击、耐疲劳、耐腐蚀等优异的特性。但是尼龙6存在低温和干态冲击性能差，吸水性大等弱点，不能满足汽车、电子、机械等行业对材料高韧性的需求。利用橡胶和弹性体对尼龙6进行增韧已经取得了很大的成功，但无法解决成本较高且基体材料刚性损失过大这一难题。实践证明，具有硬核软壳结构核壳粒子在增韧半晶性高聚物时，可以有效提高橡胶的增韧效率，减少体系拉伸强度和模量的损失。然而具有这种结构的核壳粒子合成过程复杂，成本很高，工业应用前景很小；而用传统的反应增容方法原位制备核壳粒子时，由于橡胶分子量大，黏度高，流动性差等特点限制了在反应中原位生成核－壳结构粒子的效率，影响最终的增韧效果。本论文首次尝试用低分子量的马来酸酐化聚丁二烯橡胶通过反应挤出的方法接枝改性聚乙烯，对尼龙6进行增韧，利用聚丁二烯橡胶分子链上的马来酸酐基团和尼龙6分子链的端氨基反应，在尼龙6基体中原位形成以聚乙烯为核，聚丁二烯为壳的核壳粒子，结果得到了高韧性、良好刚性的改性尼龙6。 实验证实该含有双键的低分子量橡胶能够成功的接枝到聚乙烯分子主链上，由于橡胶的马来酸酐化程度很高（14wt%），在同尼龙6共混过程中大大提高马酐基团和尼龙6端氨基之间反应生成的接枝共聚物的效率，可以有效减小两相间的界面张力，改善聚乙烯在尼龙6基体中的分散。通过透射电镜观察共混物内部形态结构发现，共混体系中形成了以聚乙烯为核，橡胶为壳的核－壳结构粒子。这种核－壳粒子对尼龙6有良好的增韧效果。当聚丁二烯橡胶的含量仅为1.5wt%时，尼龙6的冲击强度可以达到1100J/m，而拉伸强度还能保持在47.3MPa。 通过对核壳增韧体系冲击断面和拉伸力学曲线的分析我们发现，由于增韧体系中能够形成软壳硬核的核－壳结构粒子，在外力作用下，由橡胶相构成的壳结构能在聚乙烯核与基体之间形成纤维结构，这种纤维结构不仅能够改变体系的应力状态，引发基体屈服，而且大大增强了分散相粒子同基体之间的界面强度，提高体系的刚性。同时，由于两相间纤维结构的存在，材料内部形成一个类似“物理交联”的网络，材料表现出类橡胶的弹性拉伸性能，没有明显的屈服。 传统的S. Wu的逾渗理论不能很好预测这种核壳增韧体系的性能。Corté 和Leibler的模型不仅考虑了基体树脂的特性（ , , ）,而且还将分散相粒子尺寸（d）也考虑了进去，更好地预测了体系的脆韧转变点。同时在基体树脂相同，且都能增韧的前提下，可以通过Corté 和Leibler模型中参数C（代表分散相粒子能够引发基体发生屈服的能力）的大小预测增韧体系程度的大小，C值越大，体系增韧效果越好。 通过对从上述增韧体系中抽提出的原位生成的PE-g-PB-g-PA6接枝共聚物的热力学和形貌分析发现，PA6链段被限制在宽50-70nm条带状连续结构中，其运动能力受到限制，因此在结晶过程中PA6嵌段的扩散速度降低。导致在通常的结晶速率条件下（10oC/min）结晶不完善，其结晶度﹑结晶温度﹑熔融温度都有所降低，形成以γ晶型为主的不完善结晶。由于在PE和PA6链段之间由一个短的柔性PB链段相连接，因此PA6链段不能同PE发生共结晶，作为连续相PE的结晶行为受到接枝共聚物的影响要小很多。 关键词：低分子量马来酸酐化聚丁二烯橡胶，聚乙烯，尼龙6，核－壳结构，增韧，受限结晶。

HDPE-g-PB接枝共聚物的合成及其与聚丁二烯的共混

利用~(60)Co辐照合成了HDPE与丁二烯的接枝共聚物,PE-g-PB。动态力学试验表明,它与PB较PE与PB有更好的相容性。PB含量相同时PB/PE-g-PB共混物比PB/PE共混物有较高的抗张强度和断裂伸长率。前者中两相分布较均匀,相区尺寸较小。

官能化LLDPE及其合金材料(LLDPE/HIPS)的制备及结构性能研究

本文采用核磁共振碳谱、电喷雾质谱研究LLDPE-g-AA接枝产物的链结构。电喷雾质谱显示所有的丙烯酸单体都发生自聚形成低聚物，核磁共振碳谱进一步证明了丙烯酸在聚乙烯链上形成支链，并且由于反应挤出过程中的高温作用，丙烯酸支链脱水形成酸酐。丙烯酸支链在聚乙烯的结晶过程中影响链段的规整性排列，并有可能充当成核剂，使得聚乙烯晶体随着接枝率的升高变得小而不规整。接枝产物的流变行为表明丙烯酸支链起到内增塑剂作用，降低接枝产物的表观粘度，有利于产物的后加工处理。由于接枝率低的缘故，我们采用角鲨烷模拟乙丙共聚物与马来酸酐进行接枝反应。在170℃，单体浓度为2%W/V，引发剂浓度为0.2%W/V下，体系中存在马来酸酐自聚和接枝一对竞争反应。但由于存在链转移，马来酸酐大部分以单个分子形式接在角鲨烷上。对于LLDPE/HIPS共混体系，我们采用不同于以外加增容剂的办法，直接在共混过程中加入路易斯酸，利用聚乙烯本身带有或降解过程中生成的少量双键与苯发生Friedel-Crafts烷基化反应。为了找到最佳反应条件，我们研究了不同AlCl_3含量、反应时间、反应温度对增容效果的影响。增容共混物的力学性能，特别是冲击强度和微观形态照片表明加入AlCl_3后，在PE/HIPS两相界面处生成接枝共聚物PE-g-HIPS，降低界面张力，改善共混性。由于增容剂只在两相界面处生成，因此加入AlCl_3对共混物中聚乙烯组分的热学性能和结晶性并没有太大影响。

聚乙烯官能化及其与PBT共混体系结构性能研究

本工作用反应挤出接枝的方法，以甲基丙烯酸环氧丙醋和丙烯酸为单体，有机过氧化物为引发剂，对聚乙烯进行了宫能化。对文献中各种测定PE－g－GMA中GMA含量的方法进行了比较和改进，提出了一种操作较为简单可靠的方法米测定PE－g－GMA中GMA的含量。研究了单体、引发剂浓度、反应时间和反应温度对接枝率和凝胶含量的影响。引发剂浓度对交联反应的影响最大，存在一个引发剂浓度的临界值，超过这一数值，则聚乙烯熔融接枝会产生大量的凝胶。加入给电子试剂，如对－苯醌，亚磷酸三苯醋，四氯化碳等，可以使凝胶含量由17％降低到1％左右，而接枝率只有轻微的下降，由1％降低到0.8%。在低引发剂浓度和单体浓度的情况下，加入油酸可以使接枝率有显著的提高，由0.1提高到0.7%。在过氧化物引发剂中加入秋兰姆化合物，可以使自由基引发接枝反应和交联反应的程度降低，接枝率由1％降低到0.2%,熔体流动速率由0.2提高到8。而苯乙烯的加入可以使接枝率有明显的提高，由0.8%提高到1.4%。官能化聚乙烯的结晶速率随接枝率的增加而增加，但是其结晶熔融烩随接枝率的增加而降低。原因可能是接枝链既起到了成核剂的作用，又抑制了PE的结晶生长过程。对PBTILLDPE－g－AA共混物的力学性能研究表明，其断裂伸长率和冲击强度与PBTILLDPE相比有了明显提高，断裂伸长率最高可以提高5倍，非缺口冲击强度提高幅度也很大，当LLDPE－g－AA接枝率为1％时，样条未能冲断，而PBTILLDPE只有在组成为30170时才发生部分断裂，其余组分样品则完全发生脆性断裂。增容后的共混物的拉伸强度略有改善。这说明接枝到LLDPE上的AA中的竣基与PBT的端经基存在较为强烈的相互作用，使官能化的LLDPE与PBT的相容性得到了提高，从而使共混物的韧性得到了大幅度改善，强度和模量则略有改善。对共混物的形态观察表明，随共混物中LLDPE含量的增加，作为分散相 的LLDPE的粒子尺寸逐渐增加，尺寸分布也不均匀，而当共混物中加入LLDPE－g－AA后，作为分散相的LLDPE－g－AA的粒子尺寸与LLDPE相比减少了一半左右，尺寸分布也更加均匀。尽管加入LLDPE－g－AA使共混物的相容性得到改善，但当PBT作为连续相存在时，共混体系仍然表现为脆性断裂，只有当LLDPE为连续相时，共混物才表现为韧性断裂。增容后的共混物在裂纹引发区表现出塑性变形的特征，而在裂纹的不稳扩展区仍然为脆性断裂，说明相容性的改善主要是提高了共混物的裂纹引发能和稳定扩展能，因此共混物的非缺口冲击强度提高非常明显。另外在拉伸的情况下，相容性的改善使材料出现宏观的剪切屈服成颈的现象，从而使断裂能大幅度提高。加入LLDPE到PBT中，抑制了PBT的正常球晶的形成，使PBT球晶中正常球晶的含量降低，这种效应随LLDPE－g－AA中AA含量的增加而增加，而对总的结晶度的影响较小，说明共混物两组分之间的相互作用主要是使PBT的结晶形式受到影响。对官能化聚乙烯蠕变行为和动态流变行为的研究表明，官能化聚乙烯的零切粘度(3.9 * 10~4Pa.s)要高于纯聚乙烯(1.28 * 10~4Pa.s)，其熔体弹性也有显著提高，这不仅是由于分子量增加造成的，而且对接枝率比较高的官能化聚乙烯，也存在长支链的影响。共混物的粘度与共混物组成的关系在低剪切应力的情况下，符合Utracki方程。高剪切应力条件下，共混物的形态沿毛细管径向位置不同发生改变导致Utracki方程失效。Utrackl方程中的表征界面滑移因子的参数刀不仅与剪切应力有关，而且与两组分的粘弹性有关。

顺丁橡胶／聚乙烯共混型热塑弹性体的研究

利用动态交联法制备一种顺丁橡胶／聚乙烯共混型橡胶。对不同组成共混物的力学性能进行了测试，研究了共混物的组成与力学性能的关系。用动态力学方法测定了共混物的玻璃化转变温度，该共混物具有两个T_g，而且T_g的位置基本未变，说明该共混体系是不相容的。用x－射线衍射、DSC、电镜对共混物的晶态结构、热性能、形态结构进行了研究。采用辐射接枝的方法合成一种PE-g-PB接枝共聚物。探讨了聚合时间、辐射剂量对接枝率的影响。用PB和PE-g-PB共混并测定了共混物的力学性能、晶态结构、热性能以及用电镜分析了其形态结构。动态力学实验的结果表明，PB/PE-g-PB共混体系的相容性比PB／PE共混体系的好。

新型吡啶双亚胺铁催化乙烯聚合反应

合成并表征了一种新型吡啶双亚胺铁烯烃聚合催化剂2,6-二[1-(4-羟基-2,6-二甲基苯胺)乙基]吡啶氯化铁(1a)。结果表明,在亚胺环的对位引入羟基,可同时提高催化剂的活性和聚合物的分子量。在改性甲基铝氧烷(MMAO)的活化下,该催化剂引发乙烯聚合的活性(以单位时间(h)molFe引发乙烯聚合的PE质量(g)来表征)可达到6.78×106g/(mol.h),明显高于催化剂2,6-二[1-(2,6-二甲基苯胺)乙基]吡啶氯化铁(1b),且能得到更高分子量的聚乙烯。

Grafting of maleic anhydride onto linear polyethylene: A Monte Carlo study

Monte Carlo simulation was used to study the graft of maleic anhydride (MAH) onto linear polyethylene (PE-g-MAH) initiated by dicumyl peroxide (DCP). Simulation results revealed that major MAH monomers attached onto PE chains as branched graft at higher MAH content. However, at extremely low MAH content, the fraction of bridged graft was very close to that of branched graft. This conclusion was somewhat different from the conventional viewpoint, namely, the fraction of bridged graft was always much lower than that of branched graft under any condition. Moreover, the results indicated that the grafting degree increased almost linearly to MAH and DCP concentrations. On the other hand, it was found that the amount of grafted MAH dropped sharply with increasing the length of grafted MAH, indicating that MAH monomers were mainly attached onto the PE chain as single MAH groups or very short oligomers. With respect to the crosslink of PE, the results showed that the fraction of PE-(MAH)(n)-PE crosslink structure increased continuously, and hence the fraction of PE-PE crosslink decreased with increasing MAH concentration.

Compatibilization of polyamide-6/syndiotactic polystyrene blends using styrene/glycidyl methacrylate copolymers

Blends of polyamide-6 (PA6) with syndiotactic polystyrene (sPS) were prepared using a series of styrene/glycidyl methacrylate (SG) copolymers as compatibilizers. These copolymers are miscible with sPS, and the epoxide units in SG are capable of reacting with PA6 end groups. These copolymers thus have the potential to form SG-g-PA6 graft copolymers at the PA6/sPS interface during melt processing. This study focuses on the effects of functionality and concentration of the compatibilizer on the morphological, mechanical and crystallization behaviors of the blends.. In general, SG copolymers are effective in reducing the sPS domain size and improving the interfacial adhesion. About 5 wt% glycidyl methacrylate (GMA) is the optimum content in SG copolymer that produces the best compatibilization. Both the strength and modulus of the blend have been improved on addition of the SG copolymers, accompanying a loss in toughness when higher concentration copolymer is added. Incorporation of SG compatibilizers to PA6/sPS blend has little influence on the crystallization behavior of PA6 component but resulted in a steady reduction in intensity of crystallinity peak of sPS and simultaneous crystallization of sPS with PA6 is observed.

SYNTHESIS OF A POLYETHYLENE-GRAFT-POLYSTYRENE COPOLYMER AND ITS COMPATIBILIZATION FOR LINEAR LOW-DENSITY POLYETHYLENE/POLY(PHENYLENE OXIDE) BLENDS

Based on unsteady diffusion kinetics, polyethylene(PE)-graft-polystyrene (PS) copolymers were designed and synthesized with a heterogeneous high yield titanium-based catalyst by copolymerization of ethylene with a PS-macromonomer using 1-hexene as a short chain agent to promote the incorporation of the PS-macromonomer. The presence of 1-hexene facilitated the diffusion of the PS-macromonomer, giving rise to the significantly increased incorporation of the PS-macromonomer. Compatibilization of blends of linear low density polyethylene (LLDPE)/poly(phenylene oxide) (PPO) with the PE-g-PS copolymer were investigated using scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA).

Efeito da adição do poli(etileno acrilato de metila) (ema) e da fibra de linter de algodão nas propriedades do poli(tereftalato de etileno) reciclado (petrec)

The development of new materials to fill the demand of technological advances is a challenge for many researchers around the world. Strategies such as making blends and composites are promising alternatives to produce materials with different properties from those found in conventional polymers. The objective of this study is to evaluate the effect of adding the copolymer poly(ethylene methyl acrylate) (EMA) and cotton linter fibers (LB) on the properties of recycled poly(ethylene terephthalate) (PETrec) by the development of PETrec/EMA blend and PETrec/EMA/LB blend composite. In order to improve the properties of these materials were added as compatibilizers: Ethylene - methyl acrylate - glycidyl methacrylate terpolymer (EMA-GMA) and maleic anhydride grafted polyethylene (PE-g-MA). The samples were produced using a single screw extruder and then injection molded. The obtained materials were characterized by thermogravimetry (TG), melt flow index (MFI) mensurements, torque rheometry, pycnometry to determinate the density, tensile testing and scanning electron microscopy (SEM). The rheological results showed that the addition of the EMA copolymer increased the viscosity of the blend and LB reduces the viscosity of the blend composite. SEM analysis of the binary blend showed poor interfacial adhesion between the PETrec matrix and the EMA dispersed phase, as well as the blend composite of PETrec/EMA/LB also observed low adhesion with the LB fiber. The tensile tests showed that the increase of EMA percentage decreased the tensile strength and the Young s modulus, also lower EMA percentage samples had increased the elongation at break. The blend composite showed an increase in the tensile strength and in the Young`s modulus, and a decrease in the elongation at break. The blend formulations with lower EMA percentages showed better mechanical properties that agree with the particle size analysis which showed that these formulations presented a smaller diameter of the dispersed phase. The blend composite mechanical tests showed that this material is stronger and stiffer than the blend PETrec/EMA, whose properties have been reduced due to the presence of EMA rubbery phase. The use of EMA-GMA was effective in reducing the particle size of the EMA dispersed phase in the PETrec/EMA blend and PE-g-MA showed evidences of reaction with LB and physical mixture with the EMA

Role of polyethylene-graft-glycidyl methacrylate compatibilizer on the biodegradation of poly(epsilon-calprolactone)/cellulose acetate blends

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)