The Structure Study And Performance IMPR-Ovement Of Bimodel High Density Polyethyl-Ene

PE100grade pipe material is major the bimodal HDPE. The reserch is based on the Jilin Petrochemical300,000tons/year of HDPE resin synthesis device and possession of material resin products. The basic structure and properties of PE100grade pipe material were in-depth studied. The main contents of the following aspects:1. Different molecular weight distributions (MWD) of high density polyethylene (HDPE) were characterized by high temperature gel permeation chromatography (HT-GPC). Their respective rheological property, thermal property and mechanical properties were investigated. The results showed that molecular weight and its distribution were the major factors in resin performance. Crystallinity rose with increase of low molecular weight (LMW) component content. Melt flow rate (MFR) was found to be inversely proportional to the weight-average molecular weight (Mw). The larger Mw of HDPE yielded a sensitive to shear rate. The polydispersity index (PDI) increased with increasing amount of LMW component for bimodal HDPE, which had a positive effect on tensile strength and a negative effect on the impact property. The environment stress cracking resistance (ESCR) dependents on the crystallinity and molecular weight distribution of the HDPE; if the high molecular weight (HMW) component of the HDPE was similar, the ESCR was determined with crystallinity.2. The effect of low molecular weight (LMW) ethylene homoploymer on the structure and properties of bimodal HDPE was studied by blending two commercial bimodal HDPE resins (tandem reactor) with two types of LWM ethylene homopolymer. The molecule weight and molecule weight distribution, crystsallinity, rheological and mechanical properties of composites were characterized by HT-GPC, differential scanning calorimetry (DSC), capillary rheometer respectively. For composites of bimodal HDPE and LMW ethylene homopolymer, the polydispersity index (PDI) and crystallinity can be effectively increased when reduce the molecular weight of first reactor in tandem reactor. The viscosity of composites decreases at high shear rate. Increasing of LMW component has a positive effect on processing properties and tensile strength, while makes composites brittle.3. Different morphology micro-sized calcium carbonate (CaCO3) particles were prepared using aqueous solutions of CaCl2with Na2CO3over various amounts of ethylenediamine tetraacetic acid (EDTA) and different alcohols at room temperature. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. In the presence of EDTA, sphere or hemispheres CaCO3could be vastly obtained. Spindle particle was prepared in ethanol solution at room temperature. Twinsphere particle was obtained when EDTA and ethanol solution exist in all. And the growing mechanism of CaCO3particles was discussed. The sphere-like CaCO3particle was incline to form in EDTA or boric acid solution at room temperature. The surface of CaCO3was smooth in the presence of EDTA, and the crystal structure of CaCO3was major vaterite. However, the CaCO3has a rough surface in boric acid solution and is pure calcite structure.4. HDPE/4wt%CaCO3composites were prepared using a HAAKE Rotational Rheometer. The effects of the CaCO3particle morphologies and size on the thermal and mechanical properties were investigated and characterized by DSC and universal testing machine. The results show the addition of CaCO3to HDPE can increase the crystallization and decrease the melting temperature and crystallization temperature. The tensile yield strength of the composites was higher than that of HDPE. Sphere-like CaCO3is the best form in improving the thermal stability and cubic CaCO3can cause negative effect to the toughness. The impact strength of the composites is significantly increased with decreasing CaCO3particle size. SEM examination of the fracture surfaces of the composites shows that CaCO3reacted in cavitations and’lance’functions which increase the impact strength of the HDPE/CaCO3composites.