【作者】 肖岩；

【导师】 傅强；

【作者基本信息】 四川大学 ， 材料学， 2005， 硕士

【摘要】 聚丙烯(PP)是半结晶热塑性聚合物,具有密度小、耐热性好、易加工等优点,是一种综合性能优良的通用塑料。但由于其韧性差、缺口冲击强度低、缺口敏感性大等缺陷,极大地限制了聚丙烯在各个领域中的应用。为了克服这一缺点,目前仍然主要采用三元乙丙橡胶(EPDM)、聚烯烃热塑性弹性体(POE)等对其共混改性,但是弹性体的加入常常不可避免地使材料的一些性能如模量、抗张强度和熔体流动性等有所下降。而粉末纳米橡胶的出现,一方面在低用量的条件下起到增韧聚合物的作用,另一方面在一定程度上克服了传统增韧方法的缺陷。另外,要扩大聚丙烯应用范围成为工程塑料的替代,则聚丙烯的刚性和强度也需要进一步的提高。碳纳米管是近年来发展起来的一种新材料,由于其结构独特、性能优异以及具有大的长径比,它作为理想的增强材料被应用在聚合物中。 本论文综述了聚丙烯改性的发展和现状,并在此基础上介绍了本课题的立题背景。其主要目的在于通过引入粉末纳米橡胶、碳纳米管,对聚丙烯进行增韧增强,制备具有更好性能的复合材料,并讨论了结构和性能之间的关系。具体工作如下: 1.采用动态保压和普通注塑两种方法制备PP/ENP复合材料,研究了不同的加工方法对共混物形态及性能的影响。动态保压技术的引入,使得聚合物熔体在剪切力场下反复流动,高聚物分子高度取向,材料的力学性能得到明显的提高;同时,剪切力有助于橡胶的分散,在橡胶含量为2%时,动态样条的拉伸更多还原

【Abstract】 Polypropylene is a semi-crystalline polymer with some excellent properties, such as low relative density, thermal property, easy processability. However, its application is highly limited because of its brittleness at room and low temperatures. Elastomeric nano-particles have been used to enhance the toughness of PP with a small amount. Compared with traditional way, this method can achieve a good balance of toughness and stiffness of PP. In order to extend its application range, the stiffness of PP needs to be improved. Recently, carbon nanotubes have triggered considerable interest. Due to their unique structure, excellent properties and very high aspect ratio, they are used to improve the stiffness of polymer.The development and status of the modification of PP have been reviewed in this paper. The main purpose of this work is focused on preparing composites with better performance via blending PP with ENP or CNTs, studying the relationship between structure and properties. The major work of this paper is as follow:1. Two methods, dynamic packing injection molding and conventional injection molding, were used to prepare PP/ENP composites. The effect of processing method on the morphology and properties was investigated. Because the shear force introduced to the melt during packing stage can induce the molecular orientation, the mechanical property of dynamic samples was much higher than that of static samples. In addition, the shear force can help for good dispersion. At 2wt% of ENP content, both tensile strength and impact strength increased for dynamic samples, while the properties of static samples decreased. From the results of DSC and PLM, it can be seen that ENP could serve as nucleating agent, which increased the crystallizationtemperature and also caused the decreasing of crystal size.2. The viscosity of matrix and the processing method can affect the dispersion of ENP. Two kinds of PP with different MFI were used to blend with HDPE and ENP. The results showed that the impact strength keeps constant when ENP was added into the two kinds of PP/HDPE. It may be because that ENP can not have uniform dispersion and HDPE mainly act as toughening agent. Masterbatch and one-step methods were used to prepare the PP/HDPE/ENP blends. From the mechanical property of the blends, it can be seen that better dispersion of ENP could be achieved through masterbatch than one-step method.3. The brittle-ductile transition of PP/EPDM/Elastomeric Nano-Particle (ENP) was studied. Compared to PP/EPDM binary blends, the brittle-ductile transition of PP/EPDM/ENP ternary blends occurred at lower EPDM content. SEM results of the fractured surfaces of the composites indicated that at the same EPDM content, PP/EPDM/ENP ternary blends had smaller particle size, better dispersion and a smaller interparticle distance comparing to PP/EPDM binary blends, which promoted the brittle-ductile transition.4. The mechanical properties and morphology of the PP/CNTs composites were investigated, a simultaneous increase of tensile strength and impact strength has been achieved for dynamic samples of PP/CNTs composites containing only 0.6wt% CNTs. The dynamic packing injection molding could provide much strong shear force for better dispersion of CNTs in PP matrix. The result of PLM showed that the crystal size of PP decreases when CNTs was added into the matrix. It may be one of reasons that the mechanical property was improved. From the DSC result, it can be seen that the crystallization temperature increased by 10°C at 0.3wt% of CNTs content.更多还原