Praparation Of Biodegradable Plastic Film And Research Of Film's Thermal Decomposition Kinetics

The St/PVA completely biodegradable plastic film was prepared using starch(St), polyvinyl alcohol(PVA), cross-linker, plasticizer, and so on, through the process of dissolving, gelatinization and mixing, and crosslinking. Through optimization, the best reaction conditions were confirmed as follows:the mass ratio of St and PVA 7:3; reaction temperature 90℃; reaction time 1 h; glycerol loading 3%; formaldehyde loading 2%, disposable add.The soil burial test of film was researched in the lab condition and the effect of different environment factors, for example, soil fertility and pH value on the degradation of film were studied. Degradation of the film in the neutral soil was very slowly, which was worse than that in the acidic and alkaline soil. The effect of different soil pH value on the degradation of film was as follows:alkaline soil>acidic soil>neutral soil. The effect of different soil fertility on the degradation of film was distinct. Degradation of the film in the high fertility soil was very quickly, which was better than that in the medium and low fertility soil. The effect of different soil fertility on the degradation of film was as follows:high fertility soil>medium fertility soil>low fertility soil.The thermal stability of degradable plastic film was researched by the thermogravimetic analysis. Dynamical parameter of the film was calculated, and the equation of thermal decomposition kinetics was built. Based on the Kissinger and Ozawa methods, the activation energies of the pristine film were 107.27kJ/mol and 114.19kJ/mol, respectively. And the pre-exponential factor of the pristine film was 3.8925×106s-1. The corresponding activation energies of the degraded film were 275.58kJ/mol and 274.0lkJ/mol, respectively. And the pre-exponential factor of the degraded film was 7.0028×1018s-1. The activation energy of the pristine film was different from the degraded film, indicating that the degraded film requires more energies than the pristine film in the process of thermal decomposition.At last, carbamide was used as cross-linker instead of formaldehyde. The best experimental conditions were confirmed using orthogonal test:reaction time 1 h; reaction temperature 40℃; the ratio of St and PVA 6:4; carbamide loading 0.5%; glycerol loading 4%.