Oxidation of Aluminum in Mixtures with Polyethylene after Plastic Deformation at High Pressures

Powder mixtures of low-density polyethylene and aluminum with the 20–80% weight ratio of the species are subjected to plastic deformation at pressures of 1 and 4 GPa in high-pressure devices of the Bridgman anvil type. Mass changes in the deformed mixtures in the temperature range from 30 to 800◦C are studied by the method of thermal gravimetry. A mass loss associated with polymer decomposition occurs in the temperature range from 30 to 450◦C, which is always smaller than the polymer content in the mixtures. A possible reason is the formation of thermally stable products due to aluminum interaction with polymer decomposition products. In the temperature range from 450 to 800◦C, the mass of the specimens increases, which is caused by aluminum oxidation and nitridation. The mass change depends on the deformation magnitude and pressure. To separate the oxidation and nitridation processes, the thermogravimetric measurements are performed in air, nitrogen, and 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.