刚韧平衡的高抗冲热塑性聚合物材料的设计和制备

Rigidity and toughness are two key parameters that determine whether a polymer can be used as an engineering material. Polypropylene (PP), used widely as a general polymeric material, its application is limited in engineering due to its poor impact resistance, especially at lower temperature. In general, the impact resistance for PP can be improved by alloying in reactor or by blending rubber or elastomer particles into the PP matrix. However, these methods can lead to a markedly decrease in rigidity, limiting the application of PP in engineering also. Therefore, by combining the brittle-ductile transition theory and the theory of elasticity in this project, we aim to establish the relation between the critical brittle-ductile transition point and the elasticity, give the maximal value that the rigidity can reach for high impact thermal plastic polymeric material and how this value depends on the structure (crystallinity, crystal thickness, et al) and properties of matrix polymer, the structure and properties of modifier (the size and modules of core and shell), and finally design and prepare the high impact PP with balanced toughness and rigidity by melting blending, and supply the scientific basis for the industrial manufacturing of the high impact PP with balanced toughness and rigidity by allying in reactor technique.

刚性和韧性是决定聚合物材料能否用于工程材料的两个重要性能。聚丙烯作为广泛使用的通用高分子材料之一，由于抗冲击性能，尤其是低温抗冲击性能低限制了其在工程领域的应用。通过共混和釜内合金将橡胶或弹性体引入到聚丙烯基体内是制备高抗冲聚丙烯的有效方法和手段。但是，引入橡胶或弹性体增韧的同时，聚丙烯的刚性会大幅下降，这也不利于聚丙烯在工程领域的应用。因此，本项目拟将聚合物脆韧转变理论与多组分高分子体系的弹性理论相结合，建立脆韧转变临界点与材料弹性模量的关系，给出改性高抗冲热塑性聚合物的弹性模量所能达到的最高值，以及这一最高值与基体聚合物的性能和结构（结晶度、片晶厚度等）及增韧粒子的性能和结构（核壳结构）的关系，进而设计并通过物理共混的方法制备出具有高抗冲击性的刚韧平衡聚丙烯，为釜内合金技术大规模制备刚韧平衡聚丙烯提供科学依据。

将聚合物脆韧转变理论与多组分高分子体系的弹性理论相结合，建立了粒子增韧热塑性聚合物脆韧转变临界点与增韧聚合物弹性模量的关系，给出了改性高抗冲热塑性聚合物的弹性模量所能达到的最高值，以及这一最高值与基体聚合物的性能和结构及增韧粒子的性能和结构的关系式。基于这些关系式的计算和实验结果表明：（1）核壳粒子增韧聚合物比单相增韧粒子的具有更好的刚韧平衡，壳越软核越硬越有利于增韧聚合物的刚韧平衡。这一结果得到了美孚公司核壳粒子增韧聚丙烯（PP）的釜内合金产品的验证，即核为PP的核壳粒子增韧聚丙烯的刚性和韧性均高于核为聚乙烯（PE）的核壳粒子增韧聚丙烯的；（2）分别通过物理共混制备了壳为乙丙橡胶（EPR）而核为不同模量PE的核壳粒子增韧的PP，结果是核PE的模量越高，其增韧PP的刚韧平衡性越好，与理论结果一致；（3）基体聚合物自身的脆性断裂强度越高，分子量越高，分子量分布越宽越有利于其增韧后材料的刚韧平衡，并与实验结果相一致。这些研究结果为高刚性、高韧性热塑性聚合物材料的设计及其工业化制备提供了理论指导和科学依据。