相容化聚酰胺6/超高分子量聚乙烯共混物的研究
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摘要
随着汽车、机电及纺织机械等产业的发展,对具有优异性能的工程塑料需求量越来越多,单一品种的塑料很难满足综合性能的要求,采用共混改性技术,将具有不同优异性能的高聚物共混制备各组份之长,综合性能优异的塑料合金材料是近几年国内外科研人员研究的热点之一,在机械工业部技术发展基金项目的资助下,以提高汽车机械部件自润滑、高抗冲、高耐摩擦磨损及降低汽车部件重量为目标,依据高聚物共混改性的基本原理,研制了PA6/ UHMWPE塑料合金,并较系统地研究了材料制备工艺、相容性、增容剂对体系的影响、力学性能、摩擦磨损性能及机理。
    较系统地研究了作为PA6与UHMWPE共混物的增容剂HDPE—g—MAH的制备工艺,并对接枝聚合过程中的影响因素进行了分析、探讨,研究结果表明:采用反应性挤出方法,在复合引发剂体系存在下,可以制备出接枝率较高的HDPE—g—MAH共混物,通过红外光谱分析证实HDPE与MAH之间发生化学反应,MAH酸酐基团接枝到HDPE大分子链上,并探讨了引发剂加入量、单体加入量、螺杆转速及反应温度对接枝反应的影响。引发剂对体系中HDPE与MAH的接枝反应、MAH的均聚反应及大分子链自由基之间的交联反应都有影响,随着引发剂加入量的增加,接枝反应进行较快,当加入量达0.8%时出现峰值,再过量加入接枝率下降。
    单体MAH的用量增加可使接枝率提高,加入量为4%时接枝率可达到1.35%。另外反应温度和螺杆转速对接枝聚合反映影响也较大,研究结果表
    
    
    明,当温度在170—190℃、转速在30~45转/min,可制得性能良好接枝率较高的聚合物。
    本文重点研究了PA6与UHMWPE共混体系,研究结果表明:PA6与UHMWPE为热力学不相容体系,在共混体系中加入增容剂HDPE—g—MAH后降低了两相间的界面能,促进了相分散,提高了相界面的粘结力以及形态结构更加稳定,从而得出这样的结论:热力学不相容的聚合物共混体系,可以借助增容剂增加共混组份之间的相容性和强化聚合物之间的界面粘接。
    较系统的研究了增容剂HDPE—g—MAH在PA6/UHMWPE共混体系中的作用及机理,通过Molau实验、红外光谱分析、SEM及DSC分析,证实了共混物在熔融共混过程中HDPE—g—MAH的酸酐基团与PA6上的胺基或亚胺基发生了化学反应,形成了两组份间的接枝共聚物,而生成的接枝共聚物对PA6/UHMWPE体系有增容作用,分散性和界面形态以及力学性能明显改善,当增容剂增加到共混物重量的10—20%时体系的拉伸及弯曲强度提高,吸水率变小,但共混物的流变性能下降。随着UHMWPE含量的增加,冲击强度提高较明显,在增容剂为体系重量的15%时,UHMWPE为30%时,冲击强度相比PA6可提高4—5倍。
    探讨了增容剂对共混体系摩擦磨损性能的影响,随着增容剂的增加,共混物的摩擦系数减小,磨损量降低,但过多对体系有负面影响,当提高磨轮转速时,材料的摩擦系数和磨痕宽度增大,表面产生疲劳裂纹,磨损方式也发生变化,粘着磨损和疲劳磨损同时存在。
    任何一种新材料的研究都着眼于实际应用,为此,本文对研制出的PA6/UHMWPE塑料合金进行了注塑成型试验、汽车台架模拟试验及在纺织机械上的应用试验,结果表明:共混物可以采用普通的注塑成型设备及工艺进行加工,流动性好,易成型,操作面较宽,材料综合性能较好,特
    
    
    别是自润滑性,尺寸稳定性,耐吸水性,耐摩擦磨损性及抗冲击强度等性能比纯PA6有大幅提高,完全可以替代目前使用的进口件,而且成本低,加工方便,可做为汽车及纺织机械部件材料使用,同时拓宽了UHMWPE的使用范围,增加了高分子材料的品种。对PA6/UHMWPE塑料合金的研制与开发,丰富了热力学不相容共混体系改性的理论,对其它热力学不相容共混体系改性具有指导意义,并对PA6/UHMWPE塑料合金材料在汽车、纺织、化工、机械等领域的应用提供了一定的基础。
With the development of auto, machinery and power-generating equipment and textile industry, the requirements of high performance engineering plastics are increasing. Single component plastics can not meet the multiple demands. Employing blending modification technology to produce plastic alloy of excellent comprehensive properties have recently been the subject of intense interest. It is supported by the technology development fund project of Machine Industry Department. According to the aim of improving auto components self-lubricate, higher anti impact, friction and wear resistant and decreasing their weight, and the basic principle of polymer blending modification, PA6/UHMWPE plastic alloy is prepared. This paper discussed the preparation technics, compatibility, the effect of compatibilizer, mechanics property, friction and wear property and its theory.
    The preparation of HDPE-g-MAH is studied, which act as the compatibilizer of PA6 and UHMWPE, then the various effecting factors in the grafting polymerization are analyzed, such as the quantity of initiator and monomer, screw rotate speed and reaction temperature. By means of reaction extrusion, with the complex initiator exist, the HDPE-g-MAH blend of high grafting rate can be prepared. The infrared spectroscopy study shows that the reaction between MAH and HDPE is chemical reaction, and the MAH acid anhydride groups are grafted on the chain of HDPE. The quantity of initiator effect the grafting reaction of HDPE and MAH, the homopolymerization reaction of MAH, and the cross-linking reaction between radicals of macromolecule chain. The more initiator added, the higher speed of grafting reaction can be obtained, but at the point when 0.8(wt.%) initiator is added, the speed show the peak value, above this point the speed decreased as the initiator is added more.
    The grafting rate can also be increased by adding more monomer MAH, and it can be reached 1.35% when the quantity of MAH is 4%. Furthermore, reaction temperature and screw rotate speed have great effect on grafting polymerization. The study result shows that the high performance polymer with high grafting rate can be obtained at the 170~190℃ and rotate speed is 30~45r/min.
    Blending system of PA6 and UHMWPE is studied emphatically in this paper. The result shows that PA6 and UHMWPE are incompatible thermodynamics system. Putting the compatibilizer HDPE-g-MAH into the blending system can decrease the interfacial energy between two phases, and promote dispersal of phases and enhance the combination force between phases. Thus the morphology and structure are more stable. It has been concluded that the compatibility of blending system can be increased and the combination between polymers’ interfaces can be strengthened by putting the compatibilizer into the incompatible polymer blending system.
    The effect and mechanism of compatibilizer HDPE-g-MAH in the PA6/UHMWPE
    
    
    blending system are studied. The blend has been characterized by Molau, Infrared spectroscopy, SEM and DSC. The results show that the acid anhydride group of HDPE-g-MAH and amiocyanogen or imine group of PA6 take place chemical reaction, and form grafting copolymer, which act as compatibilizer in the PA6/UHMWPE blending system and improves the dispersion, interphase morphology and mechanical property. When 10~20(wt.%) compatibilizer was added the tensile strength and flexural strength were increased, absorption rate and rheological property of blend are decreased. With the increasing of the amount of UHMWPE, anti impact strength was improved obviously. Comparing with PA6, anti impact strength was increased by 4~5 times when 15(wt.%) compatibilizer and 30(wt.%) UHMWPE were added.
    The effect of compatibilizer on the friction and wear resistant property of the blending system are studied. With the increasing of the amount of the compatibilizer, coefficient of friction is decreased, wearing amount is reduced, but when too much compatibilizer is added, the effect occurs in the system. When the grind wheels’ rotate speed is accelerated,
引文
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