Oxidation of Aluminum in Mixtures with Polyethylene after Plastic Straining at High Pressures
Powder mixtures of low-density polyethylene and aluminum with the 20-80% weight ratio of the species are subjected to plastic straining at pressures of 1 and 4 GPa in a high-pressure devices of the Bridgman anvil type. Mass changes in the strained mixtures in the temperature range from 30 to 800oC are studied by the method of thermal gravimetry. A decrease in mass associated with polymer decomposition occurs in the temperature range from 30 to 450oC, which is always smaller than the polymer content in the mixtures. A possible reason is the formation of heat-resistant products due to aluminum interaction with polymer decomposition products. In the temperature range from 450 to 800oC, the mass of the specimens increases, which is caused by aluminum oxidation and nitride hardening. The mass change depends on the strain magnitude and strain pressure. To separate the oxidation and nitride hardening processes, the thermogravimetric measurements are performed in air, in nitrogen, and in argon. The thermal effects of aluminum interaction both with the polymer decomposition products and with oxygen and nitrogen are analyzed by the method of differential scanning calorimetry.