回收聚对苯二甲酸乙二醇酯的改性研究

【作者】 邱明敏；

【导师】 吴德峰；

【作者基本信息】 扬州大学 ， 材料物理与化学， 2010， 硕士

【摘要】 近年来,聚对苯二甲酸乙二醇酯(PET)被广泛应用于电子、电器仪表、汽车部件、家饰装潢等诸多行业。特别是伴随着食品行业的蓬勃发展,人们对PET中空容器以及包装薄膜等生活日用品的需求量急剧增长。不过随之而来的则是这些PET制品丢弃后引起的白色污染问题。因此,从节约能源和资源、保护环境的角度出发,对PET制品的回收及循环再利用,已是当前工程塑料研究领域的关注方向之一。但回收的PET(rPET)由于存在加工和使用的历史,因此强度低、冲击性能差、流动不稳定,难以满足工程领域对材料的要求。为此,寻求切实有效的方法来改性rPET,并建立rPET改性材料结构与性能间的关系,是回收PET制品并拓展rPET用途的关键。因此,本文首先通过熔融共混制备几种rPET改性材料:甲基丙烯酸甲酯-丁二烯-苯乙烯增韧体系(rPET/MBS)、马来酸酐接枝苯乙烯-乙烯丁烯-苯乙烯共聚物增韧体系(rPET/ SEBS-g-MAH)、玻璃纤维增强体系(rPET/GF)以及玻璃纤维和弹性体增强、增韧的三元复合体系(rPET/ SEBS-g-MAH/GF);随后研究了材料的力学强度、动态力学性能、流变性能、结晶性能以及热稳定性;在此基础上重点考察了材料的性能与其内部织态结构、填料的近、远程结构的关系;目的在于定量的评价rPET改性材料中多层次结构对宏观性能的影响程度,为该类材料的结构与性能设计奠定初步的理论和实验的基础。(1)MBS对rPET具有一定的增韧效果;当MBS含量为30 wt%时,材料的缺口冲击强度提高了约42%,但材料的拉伸强度和杨氏模量分别下降了约26%和9%。与MBS相比,SEBS-g-MAH的增韧效果更为显著,30 wt%含量的SEBS-g-MAH可使rPET材料的缺口冲击性能提高约500%,而材料的屈服强度下降并不明显;两种弹性体增韧效果的差异主要源于它们与rPET基体两相界面间的粘结程度的不同;此外,弹性体在基体中的分散形态也是影响其增韧效果的重要因素。与MBS相比,SEBS-g-MAH能够以球形液滴的形态更均匀的分散于rPET基体中。随含量的增加,其粒径逐渐减小,且符合正态分布的增韧基本特征;(2) GF增强的rPET材料同时具备优良的强度和韧性。当GF含量为30 wt%时,复合材料的拉伸强度达到108.4 MPa,与纯rPET相比提高了约115%,而弯曲模量、弯曲强度、拉伸模量以及缺口冲击强度则分别增加了534%、86%、95%和163%,材料的力学性能全面提升,且与采用Kerner和Nielsen模型预测的理论值较为接近;其中,GF的近程结构(长径比)和远程结构(取向度)是影响材料最终性能的重要参数;H-T模型分析的结果表明rPET基体中GF的有效长径比为5,远小于其初始长径比,这是由于在既定的加工工艺和基体黏度的环境中,GF为柔性填料,因此在熔融加工过程中会弯曲、缠绕甚至断裂;而与修正的COX模型获得的结果相比,Kelly-Tyson模型获得GF的理论取向度更接近实验结果。(3)采用SEBS-g-MAH和GF协同改性rPET时,在固定的SEBS-g-MAH浓度下(20 wt%),当GF含量为30 wt%时,复合材料的冲击强度提升了约445%;材料的拉伸强度以及弯曲强度则在15 wt%的GF含量下出现最大值,与纯rPET相比分别提升了约88%和63%;SEBS-g-MAH对rPET没有异相成核作用,反而会导致rPET的结晶不完善,使得体系的结晶温度和熔融温度均下降;而GF对rPET则有明显的异相成核效果,两者竞争的结果使得在较高的GF含量下,三元复合材料的熔融温度和结晶温度有所提升。更多还原

【Abstract】 As a common engineering plastic, poly(ethylene terephthalate) (PET) has been widely used in many fields in recent years. With the development of beverage industry, PET bottles are of enormously demanded. The abandoned bottles, however, have led to a serious environmental problem. Therefore, it is necessary to recycle and reuse these bottles, which is an efficient way to release environmental pressure. But rPET presents many shortcomings, such as poor flow stability and impact properties. Thus, the modification is necessary to improve the overall performance of rPET materials. In this work, rPET was toughened by methyl methacrylate-butadiene-styrene (MBS) and maleic anhydride grafted styrene-ethylene-butylenes-styrene (SEBS-g-MAH) respectively. It was also strengthened by glass fibre (GF). Four rPET materials, such as rPET/MBS blends, rPET/SEBS-g-MAH blends, binary rPET/GF composites and ternary rPET/SEBS-g-MAH/GF composites, were prepared by melt mixing. The hierarchical structure, mechanical properties, crystallization and viscoelastic behavior of those rPET materials were then studied by scanning electron microscope (SEM), dynamic mechanic thermal analyzer (DMTA), differential scanning calorimeter (DSC) and rheometer. Many mechanical models were further used to explore the relations between hierarchical structure and properties.(1) For the rPET materials toughened by elastomer: the addition of MBS could improve the toughness of rPET. At the MBS contents of 30 wt%, the izod impact strength increases by about 42% compared with that of neat rPET. But the tensile strength and Young’s modulus decrease by about 26% and 9%, respectively. In contrast to MBS, the addition of SEBS-g-MAH could improve the toughness of rPET significantly, with only small decrease of yielding strength. The izod impact strength enhances by about 500% as the SEBS-g-MAH contents achieving up to 30 wt%. The better toughness of rPET/SEBS-g-MAH blends is due to the lower interface tension and higher interfacial adhesion between two components than those of in rPET/MBS blends. SEBS-g-MAH phase is well dispersed in rPET matrix, which also contributed to toughening effect.(2) For the rPET materials reinforced by GF: as the GF contents achieving up to 30 wt%, the toughness, tensile strength, bending strength, Young’s modulus and bending modulus increase by about 163%, 115%, 86%, 115% and 534%, respectively. GF has evident reinforcing and toughening effects on rPET. Kerner and Nielsen equations can be well used to predict the tensile modulus of the composites. The aspect ratio and the orientation level of GF are the two important structural aspects determining the final properties of rPET/GF composites. Therefore, the mechanical properties of the composites were further studied by Halpin-Tsai, Krenchel-COX and Kelly-Tyson models, aiming at exploring how the short-term and long-term structures of GF affect the properties of composites. The effective aspect ratio of GF is ca. 5, which is far lower than the geometric aspect ratio of GF. This is because GF is flexible in rPET matrix, and as a result, it may be bent, entangled, and even broken off during melt mixing. Compared with those calculated from the Krenchel-COX equation, the values of orientation factor of GF calculated from the Kelly-Tyson equation is closer to the experimental results.(3) For the ternary rPET/SEBS-g-MAH/GF composite materials: as the GF contents achieving up to 30 wt%, the toughness (at the SEBS-g-MAH contents of 20 wt%) increases by about 445%. The tensile and bending strength show their maximum at the GF content of 15 wt%, increasing by about 88% and 63%, respectively. The presence of SEBS-g-MAH has no evident heterogeneous nucleating effect, while inhibiting crystallization process of the rPET matrix and reducing the crystallization and melting temperatures as a result. Contrarily, the presence of GF shows remarkable nucleating effect on the rPET, accelerating the melt crystallization and increasing the crystallization and melting temperatures. Therefore, with increasing loading levels, GF plays dominant role on the crystallization and melting behaviors of rPET matrix. Key words: recycled poly ethylene terephth alate (rPET); elastomer; glass fibre (GF);更多还原