Effect of molar ratio on thermal mass loss kinetics of poly(ɛ-caprolactone-b-propylene adipate) copolymers

Poly(ɛ-caprolactone-b-propylene adipate) copolymers were synthesized using a combination of polycondensation and ring opening polymerisation. GPC was used for molecular weight determination. 1H-NMR and 13C-NMR spectroscopy was also used for copolymer characterization and composition, which was found similar to the feeding ratio. DSC study was used in order to define Tg, Tm and ΔHm values of neat polymers and copolymers. Mass loss upon heating kinetics of neat polymers and their copolymers were studied by using thermogravimetric analysis (TGA). It was found that copolymers have almost the same thermal stability as PCL, which is the most stable part. The influence of PPAd in copolymers can mainly be seen at the beginning of mass loss where a small overlapped peak can be observed. The kinetic parameters of mass loss upon heating of all polyesters were calculated while the activation energies were estimated using the Ozawa, Flynn and Wall (OFW) and Friedman methods. Mass loss upon heating was found to be described by two mechanisms that follow each other. The first mechanism is attributed to a small mass loss, while the second mechanism is attributed to the main mass loss as in autocatalysis nth-order (reaction model Cn) or nth order (reaction model Fn).