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Thermo gravimetric analysis on the effect of dimethyl terephthalate plasticizer on thermal degradation of polystyrene

Khalid E.Al Ani, Mohammed Al Omari, Basim Nasralla

The thermal degradation behaviours of polystyrene plasticized with dimethyl terephthalate was studied by thermogravimetric (TG) analysis. The effect of added plasticizers on thermal degradation was also investigated under dynamic conditions (30-550oC) in pure nitrogen gas, at the heating rates 5,10,15, and 20oCmin-1. The characteristic of the TG curves were determined. These can be used to indicate the thermal stability of polystyrene films. Kinetic parameters, such as the activation energy (E), and the pre-exponential factor, (A) were calculated using the Flynn-Wall-Ozawa and Kissinger methods. The thermogravimetric (TG) curves of dynamic degradation of PS and PS doped with dimethyl terephthalate plasticizer were, obtained in the temperature range 30-550oCat the heating rates 5,10,15, and 20oCmin-1. PS doped with dimethyl terephthalate plasticizer showed an acceleration of photodegradation at higher temperatures in comparison with the non-plasticized PS films. It is evident that the thermal degradation of pure PS proceeds by one-step process between 400 and 550oC, which represent by a single peak in the corresponding DTG curves. The thermograms of PS/DMT blends show two unresolved degradation steps, the first corresponds to the thermal degradation of DMT and the second to the thermal degradation of PS.