Study On Modifications Of HDPE/MTH Composite

The research on the use of magnesium hydroxide(MTH) as a main flame retardant in high density polyethylene (HDPE) was performed. The effects of MTH on the combustion characteristics were studied. It has been found that more than 60 % by weight of MTH was required to obtain an adequate level of flame retardant property of HDPE, and such high loading levels of MTH damaged the mechanical properties of the filled materials seriously. The studies of the synergistic effect between MTH , some other halogen-free flame retardants and mechanical properties such as zinc borate (ZB), microcapsulated red phosphorous (MRP), expandable graphite (EG) and ferrocene in HDPE were conducted. It was found that there was a great synergistic effect between MTH and EG on improving flame retardancy of the composite and between MTH and ferrocene on improving the capacity of smoke emission. But mechanical properties were damaged to some extent because of loading synergistic agents.The effects of surface modifiers e.g. stearate acid, silane coupling agent, titanate coupling agent and hydroxide silicone oil on the properties of the HDPE/MTH composites were studied. A great increase of the elongation at break of the HDPE/MTH composites with surface modifiers was found, compared with the composites without the modifiers. The addition of surface modifiers led to a decrease of flame retardation of the HDPE/MTH composite. The scanning electron microgragh (SEM) photoes of fracture surfaces of the above composite containing modifiers showed that MTH particles were well dispersed into the polymer matrix and that many debonded MTH particles were not clearly seen on the fracture surface.The compounded fire-retardant composed of MTH and Br-Sb halogen retardant was studied and the optimum ratio was found. The result showed the effects of compounded flame-retardant on flame retardant properties, mechanical properties and flame properties were better than the effects on MTH. The compounded flame-retardant gathered merits both MTH and Br-Sb halogen retardant such as better flame retardant and low loading, etc. But its defect was more smoke than MTH's .SEM photoes which analyzed the microstructure of residues after burning showed the combustion mechanism of compounded flame retardant that was the result of corporate action of both solid combustion and gas combustion.To crosslink HDPE system with dicumyl peroxide (DCP) at proper crosslinking...