B. Gupta et Gg. Scherer, RADIATION-INDUCED GRAFTING OF STYRENE ONTO FEPA FILMS - STRUCTURE ANDTHERMAL-BEHAVIOR OF COPOLYMERS, Die Angewandte makromolekulare Chemie, 210, 1993, pp. 151-164
Thermal characteristics of radiation-grafted FEP-g-polystyrene copolym
er films were evaluated using thermogravimetric analysis (TGA) and dif
ferential 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 th
e loss in the FEP component was observed. DSC studies showed that the
heat of fusion was reduced in the grafted FEP samples. This was attrib
uted to the dilution of inherent crystalline zones by the incorporatio
n 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 fil
ms were found to be higher as compared to that in ungrafted FEP and ho
mopolystyrene films. These results have been explained in terms of the
decrease in the segmental mobility of macromolecular chains in the gr
afted films.