Research On Modification Technology And Properties Of PBAT-Starch Degradable Plastics

Since the 21st century,with the rapid development of take-out and express delivery industries,plastic packaging products and disposable plastic tableware have been more widely used,which has brought about serious"white pollution"problems.Biodegradable materials are considered to be the most effective solution to the"white pollution"problem.Biodegradable plastic poly（butylene terephthalate adipate）（PBAT）has good toughness,heat resistance and biodegradability,and is a hot spot in the research of biodegradable materials and has wide application prospects.With the gradual implementation of"plastic restriction"nationwide,there is a high demand for PBAT mechanical properties,thermal processing properties,cost and multifunctionality,and the research of PBAT composites is crucial.In this paper,PBAT,calcium carbonate（CaCO₃）and starch were selected as the main raw materials to improve the comprehensive properties of PBAT composites and reduce the production cost.Three PBAT blending systems,namely,PBAT/CaCO₃ system,PBAT/CaCO₃/starch system and thermoplastic starch（TPS）/PBAT system,were studied by melt blending materials with twin-screw extruder and torque rheometer,and the density,mechanical properties,hot workability,hydrophilicity-hydrophobicity,thermal stability and micro-morphology of the corresponding products were tested and characterized.The effect of CaCO₃ on the properties of PBAT composites was studied.The results showed that the size and content of calcium carbonate particles significantly affected the tensile properties of composites;The addition of unmodified calcium carbonate decreased the tensile properties of the composites by more than 30%.Comparing with six commonly used coupling agents,it was found that titanate coupling agent（TC）modified calcium carbonate was more effective in improving the mechanical properties and hot workability of composites.The tensile strength of the composites made of titanate coupling agent TC-201 modified calcium carbonate could reach20.55 MPa,which was 28.60%higher than that of unmodified calcium carbonate.Moreover,TC-201 modified calcium carbonate could effectively improve the thermal stability and hydrophobicity of the composites.The decomposition temperature of calcium carbonate increased from 546.5°C to 566.1°C,the water contact angle of the composite film increased from 85.7°to 94.6°,and the water absorption rate decreased from 13%to 1%.In order to reduce the density of composites,modified starch was selected to replace part of CaCO₃,and the effects of CaCO₃ and modified starch on the properties of PBAT composites were studied.The results showed that the tensile strength of the composites decreased by nearly40%when the amount of surface modified starch was gradually increased from 0%to 12%.The hydrophobicity of the composite decreased,the water absorption of the film increased from 2%to 14%,and the water contact angle decreased from 93.6°to 84.2°.The density of the composite decreased from 1.48 g/cm³ to 1.35 g/cm³ when the content of plasticized modified starch gradually increased from 0%to 12%.The tensile properties first increased and then decreased,and the tensile strength reached 18.12 MPa.The hydrophobicity of the composite decreased,the water absorption of the film increased from 2%to 10%,and the water contact angle decreased from 93.6°to 89.7°.The effect of plasticizing starch modified PBAT was obviously better than that of surface modified starch.The effect of TPS on the properties of PBAT composites was further studied.The results showed that polyols weaken the interaction of hydroxyl groups in starch molecules by interacting with hydroxyl groups in starch molecules,and improved the hot processability of starch.The shorter the carbon chain length of plasticizer molecule,the more hydroxyl groups it contains,and the better the plasticizing effect.The tensile strength,elongation at break and impact strength of the composites prepared from glycerol plasticized starch were 5.36 MPa,23.28%and 1.73 k J/m²,respectively.The tensile strength,elongation at break and impact strength of the composite prepared from sorbitol plasticized starch were 20.25 MPa,7.26%and 0.56 k J/m²,respectively.When the addition ratio of glycerol/sorbitol was 5/25,the tensile strength of the material reached the highest,reaching 25.07 MPa,the elongation at break was 10.23%and the impact strength was 0.73 k J/m².With the increase of glycerol content,the contact angle of the composites increased from 62.7°to 80.5°,and the hydrophobicity of the composites increased obviously.