Study On The Mechenism Of Low Temperature Thermooxidation And Degradation Of Polyethylene

In this paper the degradation mechanism of the low-density polyethylene(LDPE) as a film was studied with the diphenyamine (DPA) antioxidant as a freeradical catcher. Taking the N- butyl diphenylamine as the flame of reference, thestructural changes of the DPA was investigated by Thin Layer Chromatograph(TLC) and Ultra-violet spectrograph (UV). The degradation products of LDPEwere identified by the Infrared spectrum (IR). Some results have been foundwhen polyethylene was under irradiated by UV light of 375W and undersimulating composting temperature.1,The results showed that under UV light of 375W condition, the LDPE hasdegenerated without any initiator but the starch. Carboxylic acid and the N-alkyl diphenylamine were founded in the degradation products. It showed thatthe degradation mechanism of the low-density polyethylene is a free radicalmechanism. Some small fragments of the alkyl free radical were produced in thedegradation process. It is remarkable that the same phenomenon did not found inthe pure PE sample. So it was considered as the induction of starch effect on thepolyethylene photo-degradation.2,The results showed that multi-hydroxyl ethers have obvious promoted thedegradation of LDPE under simulating composting temperature. It is indicatedthat the degradation can be explained with a free radical mechanism. The oxygen in environment has great influence to the degradation. The results ofFTIR showed that the compounds containing carbonyl, hydroxide groups are theultimate degradation products of the hydroperoxides and other dominantmedium products. The rusults of DSC showed that the degree of crystaUinityincreases with the composting time. Some small fragments of the alkyl freeradical were produced in composting process.