An intensive exploration of plasticization, tensile, flexural and ecotoxicity of styrene-grafted thermoplastic starch (TPS) composite material

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Thermoplastic starch (TPS) is a potential alternative to non-biodegradable plastics. Nevertheless, nice hydrophilicity, poor mechanical property and processability restrain use. Herein, pure corn starch was modified by styrene grafting, then, plasticized by glycerol to prepare TPS composite material. Later, plasticizing behavior, thermal-stability, mechanical property, ecotoxicity, etc. were explored. Main results reveal that styrene was successfully grafted to starch achieving a grafting yield (GY) as 45.58 wt% and grafting converted starch crystalline shape transformation from A to V. Glycerol plasticization furtherly altered crystalline structure and surface wettability. To native species, plasticization induced amorphization; to grafted species, it induced crystalline perfection. Compared to native species grafted starch displayed easier plasticization characteristic and better processability, elevated hydrophobicity and mechanical property. Herein, a glycerol content as 20 wt% is proper. From native to grafted TPS composite material tensile, flexural strengths and modulus were elevated from 8.9, 20.9 and 777–24.2, 56.5 and 1924 MPa. A more important issue is that styrene grafted TPS composite material composting products displayed no-visible ecotoxicity. Where, wheat and mung seeds germination rates and plant fresh and dry masses in systems containing 10 wt% previous TPS composting products are all higher than 90 % those of blank compositing systems, which is in line with EN 13432–2000 standard, non-toxic to environment. It seems via some level styrene grafting possessing nice mechanical property and non-visible ecotoxicity starch material can be prepared, possibly having a potential use in plastic industry in real, which is of great significance and attractive.