(570o) Binary Interaction Between Polyethylene and Polypropylene: Effects On Thermal Degradation and Product Distribution

The present work investigates the presence of any interaction between constituent plastics in a mixture by studying their binary mixture pyrolysis kinetics in a Thermo-gravimetric Analyzer (TGA) and further by studying their product distribution by using a Gas Chromatograph (GC). Binary mixtures of low density polyethylene (LDPE) and polypropylene (PP) were studied. Synergistic effect was indicative in their DTG (derivative thermogravimetry) plot, which manifested itself by shift in the maximum degradation temperature (Tmax) to a lower value. Non-interacting decomposition curves were drawn on the assumption that decomposition of each plastic in the mixture is completely independent. These curves deviated significantly from the experimental TG (thermogravimetry) and DTG curves, which made it evident that synergistic effect existed between the plastics. An interacting model was formulated which could successfully mimic the degradation behavior of the plastics. Then we focused our attention on the possible effect of synergism on the product distribution from pyrolysis of the mixtures at different stage of their degradation. Firstly, product distribution studies for a wide range of hydrocarbons (C5-C44) were carried out for the single plastics over a wide range of temperature (200-600oC), and the same has been explained with mechanistic pathways of decomposition. Then, product distribution was studied for the binary mixtures over the same temperature range. And as expected, product evolution pattern for binary mixtures was found to be different from the single plastics. The same could be explained based on mutual interaction between PP and LDPE. Thus, synergistic effect that was observed in the decomposition kinetics of the plastic mixtures was further justified by the product evolution pattern in their binary mixtures. The same concept could be extended towards other mixtures, and by varying their proportion, experiments could be designed to get optimum yield of desired hydrocarbons.