Polyethylene Expansion Of The Flame Retardant System

Polyethylene (PE) is widely used in many industries such as electric, chemistry and machine. But flame retardancy is needed for its low LOI, flammability and dropping when burning. Compared with others, flame retardant methods by intumescent flame retardant (IFR) system of polymer is more excellent for halogenless, low-smoke and low-toxic. Recently, the research and development on IFR is flourishing abroad and some IFR reagents are on the market, which just began in our country and was much less on PE-IFR.In this paper, the IFR system based on PE, including ammonium polyphosphate (APP), pentaerythritol (PER) and melamine (MN) was studied. Experiments were arranged by means of second-order regressive orthogonal design. The second-order regression equations for LOI had been established. Prediction of the LOI and experimental verification were also made.Taking LOI and vertical burning methods as main measures to estimate the flame retarding efficiency of materials, the effects of each ingredient were studied. With the aid of thermal analysis (TGA and DTA), the mechanism of chemistry reaction, intumescence and charring were discussed.The action of anti-dropping by adding line phenolic-formaldehyde resin (LPF) into PE-IFR was studied. Configuration and structure of intumescent char was observed with SEM and the mechanism of anti-dropping was discussed.Based on those experiments, a mathematic model of process of intumescence was established with the neglect of the transfer motion of the bubble. Approximate solutions were found for the rate of growth of a bubble in the process of intumescence.