The effects of foaming and annealing on mechanical properties and DSC scans of gas saturated and non-gas saturated high impact polystyrene

A series of high impact polystyrene (HIPS) specimens was prepared under dif ferent processing conditions to study the effects of CO2 sorption and annea ling conditions on thermal response and mechanical properties of gasified a nd/or foamed materials. The process variables included gas-saturation, non gas-saturation, foaming temperature and annealing temperature. In this stud y, samples were first saturated with CO2, foamed if necessary then desorbed , and finally followed by sub-T-g annealing. The thermal response and mecha nical properties followed the opposite trend of materials which were first sub-T-g annealed then exposed to CO2 performed by previous workers. This su ggests that gas sorption and annealing produce opposite effects. Gas sorpti on followed by annealing may annul a portion of the gas sorption effect, an d vice versa. The glass transition temperature is an important factor that affects the trend of the results of mechanical properties in the foamed the n annealed materials.