Studies on Thermal Degradation of Synthetic Polymers (Part 10)

Thermal gasification of polyethylene (PE), polypropylene (PP), and polyisobutylene (PIB) was carried out under atmospheric pressure using the flow system of a fixed bed reactor. From an experimental equation, IF=Tθa, product yields were estimated, where IF is the intensity function (°C•seca), T is the reaction temperature (°C), θ is the residence time (sec), and a is a constant (-). The effect of the structure of polyolefin on the value of "a" was also discussed.The pyrolysts conditions used in this study were as follows: temperature, 500∼800°C; the residence time, 0.6∼7.1sec; and the dilution ratio of steam to polymer by weight, 0.6∼7.5.The operating factors were inferred to be reaction temperature and residence time. For a given product yield, these two factors were interchangeable. Equations for yielding methane were expressed as_follows: (PE): IF=Tθ0.04, (PP); IF=Tθ0.05, (PIB); IF=Tθ0.07.As IF was correlated to the product yield, the product yield could be predicted by some appropriate choice of pyrolysis conditions. The value of "a" of a polyolefin was correlated to the activation energy (ΔE) for thermal degradation and to temperature (T1/2) corresponding to 50% weight loss. These two parameters were determined from the TG curve.