The polystyrene density is between 1.41 and 1.43 grams per centimeter and its melting temperature is 165 to 175 degrees Celsius. If polystyrene is placed at a temperature above its melting point, the polymer decomposes and releases toxic gases. DMF (Dimethyl Formidamide), Dichloro Benzene, and Dimethyl Benzene Solvent Solvents have a polystyrene glass transfer temperature of minus 75. C. When polystyrene burns hard, it burns in the flame and continues to burn. The flame is blue and invisible. It also burns smoke-free polystyrene, drips into the flame and releases a toxic odor (formaldehyde odor).