thermal-oxidative degradation of pga, plla, and random binary plla-pga copolymers

Dimerization process is essential for producing copolymers. the features of dimerization process likethermal‐oxidative degradation should be well known to reach maximum efficiency and a superiorreactor design. also, the degradation mechanism of biodegradable polymers is important duringsterilization processes. thermal‐oxidative degradation of pga, plla, and their binary copolymers wasinvestigated under isothermal heating as well as dynamic heating. all the samples were prepared by apolycondensation process and were characterized by tg, dtg, dsc, and hnmr analyses. activationenergy under dynamic heating was obtained by using friedman plot. a new three stage mechanism,namely random, transition, and specific stages is proposed for dynamic heating degradation. isothermalheating investigation is conducted under an inert atmosphere, and frequency factor and activationenergy were achieved. it was found that the activation energy under isothermal heating is generallyhigher than that under dynamic heating. it was found that the rate of degradation increases significantlywith an increase in temperature. the effects of pressure on the degradation rate were studied indifferent atmospheres with various oxygen partial pressures. pressure effect was correlated by a secondorder polynomial in terms of total pressure. the obtained activation energies under isothermal heatingwere in good agreement with those reported by others. the complete kinetic scheme suitable forreactor design for the thermal‐oxidative degradation of the samples was reported. finally, the optimaloperational conditions for the dimerization process were reported