Thermal degradation kinetics and estimation of lifetime of polyethylene particles: Effects of particle size

The thermal stability and degradation behavior of polyethylene (PE) particles having a diameter varies from few nanometers to micrometers were studied by thermogravimetric analysis (TGA). The PE particles of average diameter similar to 20, similar to 10, similar to 1 mu m and <500 nm were studied over a range of temperatures from 25 to 600 degrees C in N-2 atmosphere and heating rates of 5, 10 and 15 degrees C min(-1). The three single heating-rate techniques such as Friedman, Freeman-Carroll, and second Kissinger; and three multiple heating-rate techniques such as the first Kissinger, Kim-Park and Flynn-Wall were used to work out the kinetic parameters of the degradation reactions, e.g., activation energy (E-a), order of reaction (n) and frequency factor [ln(Z)]. The lifetime of macro, micro and nanosized PE particles were also estimated by a method proposed by Toop. It was found that the activation energy and lifetime of nanosized PE nanoparticles were moderately high compared to the micron sized PE particles. Moreover, the decomposition temperature, order of reaction (n), frequency factor [ln(Z)] do not only depend on heating rates and calculation techniques, but also on particle size of the PE. The results obtained from the kinetic and lifetime studies for nano and micro sized particles were compared with macro sized PE. (C) 2008 Elsevier B.V. All rights reserved.