Effect Of Structure On The Rheology And Other Performances Of High Density Polyethylene

With the rapid development of modern polyolefin industry, polyethylene (PE) has occupied the largest share in today's world as one of the most important resin. Because of its good toughness, low cost, convenient processing and excellent chemical resistance, PE plays an increasingly important role in every walk of life. Meanwhile, the requirements of polyethylene's performance were raised higher and higher, and how to use low-cost ways to get polyethylene with high performance has become the frontiers in polymer chemistry research and application.There are three ways to produce high performance PE in general:1) The development of new PE; 2) Chemical modification; 3) Physical modification. Developing new products takes a long life cycle and high cost, therefore the chemical and physical modification are the main way to improve the performance of PE. However, the blind modification without goals would result in a tremendous waste of resources. Therefore, the premise of producing the high performance PE was to study the influencing factors for the PE's performance.We focus on the factors that affect the performance of polyethylene on three aspects:1. The effects of the physical properties of PE on their own performance before modifications. The factors such as the density, molecular weight, molecular weight distribution and long branched-chain structure have been extensively studies and widely accepted, so we focus on the effect of structure and degree of short branching on the performance of high density polyethylene. A series of experiments verified that the structure and degrees of short branching of polyethylene have different grade influence on the mechanical properties, rheological properties and crystallization properties, respectively.2. The method of the chemical modification is to graft the 2-Ethylhexyl acryl ate (EHA) to the PE to form long-branched-chain structure, and the performance of PE-g-EHA with different dosage of EHA were also investigated. A series of experiments show that the EHA can graft on PE under appropriate initiator and reaction temperature. After the chemical modification, the rheological properties, crystallization and mechanical properties are changed. Moreover, the reaction mechanism has been discussed.3. The method of physics modification is to take the popular nano-particles as filler material to study the performance of PE with different amount of nano-SiO2. Since the poor compatibility between PE and nano-SiO2, large agglomerates of SiO2 particles were observed in the PE matrix. On the contrary, the nano-SiO2 modified by aluminate coupling agent dispersed evenly in the PE matrix. Experiments show that the difference of nano-SiO2's contents would influence the performance of PE. The performance of PE will have an optimal value when the filler content in a certain value, then the performance will decline with the increase of filler content.