RADIATION-INDUCED GRAFTING OF STYRENE ONTO FEPA FILMS - STRUCTURE AND THERMAL-BEHAVIOR OF COPOLYMERS

Thermal characteristics of radiation-grafted FEP-g-polystyrene copolymer films were evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The grafting of polystyrene onto FEP film introduced a two-step degradation pattern where polystyrene degradation occurred in the range of 400-460-degrees-C beyond which the loss in the FEP component was observed. DSC studies showed that the heat of fusion was reduced in the grafted FEP samples. This was attributed to the dilution of inherent crystalline zones by the incorporation of amorphous polystyrene grafts into the amorphous region of the FEP matrix. The melting temperature, on the other hand, remained constant for the entire range of graft levels (0-40%). All the copolymer films exhibited two glass transition temperatures (T(g)) each corresponding to the FEP and polystyrene moieties. However, the T(g) in grafted films were found to be higher as compared to that in ungrafted FEP and homopolystyrene films. These results have been explained in terms of the decrease in the segmental mobility of macromolecular chains in the grafted films.