Studies On Preparation And Properties Of HDPE Modified By Core-Shell Nano-CaCo₃/POE

High density polyethylene（HDPE） is one kind of commercial resins. It is widely used in the fishery field for its lightweight, excellent wear resistance and low price. With the development of distant water fishery, the fishing materials have a higher demand for its overall performance, especially toughness. The toughness can be improved by adding elastomers. However, the cmposites which was modified with elastomer have a shortage of low strength. Thus, the researches of HDPE with high strength and high toughness have attracted a lot of interests. Inorganic nanoparticles are rigid particles, which can improve the strength of the composites, but nano-fillers are difficult to achieve uniform distribution in polymer matrix and easily gathered into cluster. In anattempt to solve the above problems, HDPE was toughened by rigid particles nano-Ca CO₃ and elastomer POE, and then HDPE/nano-Ca CO₃/POE ternary composites were prepared by different blending processes. The influnces of the blending processes, the contents of nano-Ca CO₃, POE on the micro-morphology, crystallization property, thermal degradation, rheological property and mechanical properties of the ternary composites; and the relationship between performance, structure and process of the ternary composites have been investagted; which can provide the theoretical basis for the preparation of high strength and high toughnesse HDPE. The main research contents were summarized as follows:（1） The effects of blending technology and the contents of nano-Ca CO₃, POE on the phase morphology of the ternary composites. It was observed that the distribution of nano-Ca CO₃/POE becomes more homogeneous by employing two-step method, and the nano-Ca CO₃/POE particles with core-shell structure well distributed in the matix. The morphology and size of the core-shell structure were effected by the content of nano-Ca CO₃ and POE in the ternary composites, the nano-Ca CO₃ well distributed when the content of nano-Ca CO₃/POE in the ternary composites was 5 wt.%. When the content of nano-Ca CO₃ was overdose, it can be easily agglomerated in the matrix, and the size of the core-shell structure decresed first and then increase with the increasing content of POE in the ternary composites. The core-shell structure（100nm-300mm） with POE as shell and nano-Ca CO₃ as core was well distributed in the matix of HDPE/nano-Ca CO₃/POE（90/5/10）prepared by using two-step method.（2） The crystallization property was investigated by WXRD. The resaults showed that the blending processing and the adding of nano-Ca CO₃, POE have not changed the crystal structure of HDPE, but effected the crystallinity of HDPE. The crystallinity of pure HDPE is 65.13%, and crystallinity of the composites decreased because the regularity of the molecular chain was destructed by the core-shell structure. The crystallinity of the composites decreased as the content of POE increased, and when the content of POE was 17.39%, the crystallinity of the composites was 59.60%, which was 8.49% decreased than that of pure HDPE.（3） The thermal degradation property was analysised by TGA. The initial temperature of thermal degradation and maximum degradation temperature was 386℃, 470℃, respectively. The blend processing and the content of nano-Ca CO₃ had almost no effect on the thermal stability properties. The maximum degradation temperature was almost unchanged when the content of POE was less than 9.5wt.%, but as POE content continues to increase, the maximum degradation temperature declined with increasing POE content. The initial and maximum temperature of thermal degradation was 365℃, 465℃ respectively when the POE content was 17.4% in HCP20. In order to maintain the thermal stability of the composite, POE content should be controlled within a certain range.（4） The study of mechanical properties showed the blend technology had great effect on the mechanical properties. The mechanical properties of composites H（95）/Ca:P（1:4） prepared by using two-step method was better than that using one-step method. The POE can improve the toughness greatly, while the nano-Ca CO₃ can enhance the breaking strength, but the POE and nano-Ca CO₃ can toughen HDPE synergistically. The HDPE/nano-Ca CO₃/POE（90/5/10） ternary composites prepared by the two-step method had good mechanical properties, and the fracture strength was 35.17 MPa, which was improved by 12.26% than that of pure HDPE, and the elongation at break was 630.08%, which was 20.90% than that of pure HDPE, the composites not only maintained the strength, but also improved the toughness.