ESR STUDY ON PEROXIDE MODIFICATION OF POLYPROPYLENE

Chemical modification of isotactic polypropylene via a free-radical me chanism was studied using an on-line electron spin resonance spectrome ter. Peroxides were used to provide primary radicals upon thermal deco mposition at elevated temperatures for the generation of polymer backb one radicals. Four types of peroxides, tert-butyl perbenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyne-3, and benzoyl peroxide, at various concentration levels were employed. The ESR meas urement demonstrated that the modification was accomplished via a free -radical mechanism. Both radical generation and termination were clear ly observed. Peroxide type, concentration, temperature, and reaction t ime were the major factors that affected the radical concentration pro files. The radical concentration variations were used to estimate the radical termination rate constants.