Comparative Study On Pyrolysis Character Of Waste Plastic Between Hard And Soft Polyurethanes

Polyurethanes are macromolecular polymers which have well performances in chemical and physical. They replace the parts of older plastic and are applied in many spheres, such as construction industries, aerospace, automotive, medical. But how to treat and utilize refused plastic was produced, which is a severe environmental problem. The common treatment, such as landfill and direct incineration, cannot fit to environment now. Chemical decomposition was applied as a better treatment which is beneficial to economic and environment. In this paper, pyrolysis was adopted for comparing hard and soft polyurethanes in experiment and mechanism to analysis distribution of products and get activation energies.Comparison of TG and DTA curves of two polyurethanes, the result that decomposition of polyurethanes is a multitude of physical and chemical processes was confirmed. The initial degraded temperature increases, maximum decomposition velocity decreases and the whole decomposition process moves to higher temperature range with heating rate elevated. The components of hard polyurethane composed between 200℃and 410℃, as well as, soft polyurethane appeared between 170℃and 500℃. In nitrogen and at four different heating rates, experiments of two kinds of polyurethanes were operated. Following the pyrolysis temperature given increasing, solid residues decreased and it is in favor of thermal decomposition. With heating rate increasing, solid and gas products were increased and liquid product decreased. Longer residence time more liquid and gas products and less solid residue. By GC/MS analysis, Aniline and P-Aminotoluene all were detected in liquid products of hard and soft polyurethanes. And five main chemical component in products of hard polyurethane and eleven ones in soft polyurethane were shown. Fatties in soft polyurethane are the key of difference of two polyurethanes. The elementary reaction for styrene was forecasted by Chemkin software. It was produced from C4H6,C6H8,C6H5 and C2H4 through a series of elementary reactions. For studying pyrolysis kinetics, a kinetic model was built. By this way, a series of kinetics parameters of polyurethanes at different heating rates were gotten. The activation energy of hard polyurethane decreased following heating rate improved, in contrast, the trend of the activation energy of soft polyurethane increased. The average activation energies of hard and soft polyurethanes are 127.7KJ/mol and 203.1KJ/mol respectively. That of soft polyurethane is 1.59 times as many as one of hard polyurethane.