Thermal studies on the starch-g-copolymers prepared from two terpene acrylate monomers under oxidative conditions

The simultaneous thermal studies (TG/DTG/DSC) coupled with the FTIR analysis of the gaseous decomposition products created under oxidative heating of starch-g-poly(neryl acrylate) and starch-g-poly(geranyl acrylate) copolymers have been presented. To these studies, the copolymers with the following grafting percents (G) were selected: starch-g-poly(neryl acrylate) copolymers: 36.6 +/- 0.3%, 40.3 +/- 0.4%, 42.8 +/- 0.4% and starch-g-poly(geranyl acrylate) copolymers: 28.9 +/- 0.2%, 32.4 +/- 0.6%, 35.6 +/- 0.4%. The performed tests proved that the thermal resistance of the copolymers was strongly dependent on their G values, despite a small difference in the G values between the samples. The slight increase (ca. 6.2-6.7%) in the G value caused the significant drop of the thermal stability of all the studied materials. The TG/DTG/DSC studies confirmed at least three-stage decomposition mechanism of the copolymers where simultaneous pyrolysis, oxidation, dehydration and decarboxylation processes took place. The TG/FTIR analyses showed the emission of various structure fragments; among them, one can mention the creation of some organic fragments such as aldehyde, acid, alkene, alkane, furan fragments, CH4 and inorganic species (CO2, CO, H2O) as a result of the oxidative decomposition processes of the studied copolymers. In addition, the conducted studies demonstrated similar decomposition course and mechanism for both types of the copolymers, regardless of the monomer type used to the graft process.