Research On Preparation And Properties Of The Biodegradable Composite Material Based On Poly (Butylene Adipate-Co-Terephthalate)

Polybutylene adipate terephthalate（PBAT）is an excellent biodegradable polymer material with good biodegradability,mechanical properties such as flexibility and elongation,etc.However,compared with LDPE materials,the melt strength of PBAT polymer is low,the processing performance is poor,and the price is expensive,which limits its application and promotion in some fields.Therefore,it is often modified by blending.In this study,PBAT/inorganic filler composite materials were prepared by melt blending,and the effects of filler type and content,twin-screw extrusion process,and screw combination on the blend and blown film properties were investigated.（1）The effects of modified talc（Talc）content on the rheological properties,melt strength,crystallization performance,thermal stability,microstructure,and mechanical properties of PBAT/Talc blends were studied.The results showed that modified talc has good compatibility with PBAT resin matrix.Increasing the talc content can significantly improve the melt strength of the blend and reduce the thermal degradation rate of PBAT.However,the increase in filler content will exacerbate the spatial hindrance caused by Talc to molecular chain movement,leading to a decrease in crystallization rate and degree of crystallinity.When the Talc content is 20%,the mechanical properties of the composite film are optimal,and the tensile strength and elongation at break are 33.59 MPa（MD）,580.36%（MD）,32.16MPa（TD）,and 615.82%（TD）,respectively.（2）PBAT/Talc-Ca CO₃ blends with modified talc and modified calcium carbonate（Ca CO3）as composite fillers were prepared using a two-step method,and the mechanism of enhancing toughness of the blend by dual fillers was studied.Talc can form a stable intercalation structure with PBAT,increase the physical entanglement and chemical cross-linking between it and molecular chains,and the sheet-like talc can promote the crystallization of PBAT-based composite films,enhance intermolecular forces,and thus improve material rigidity.The particulate Ca CO₃ is not easily adsorbed by other substances on the surface,which makes it have a self-lubricating effect,effectively improves the ability of molecular chain movement and the uniformity of filler dispersion.Secondly,the addition of Ca CO₃ also increases the interlayer spacing of talc in the resin,even destroys the intercalation structure,and effectively improves the toughness of the material.When the total content of talc and Ca CO₃ is 40%and the compounding ratio is 3:2,the comprehensive performance reaches the maximum value,and the tensile strength and elongation at break are31.23 MPa（MD）,490.87%（MD）,30.45 MPa（TD）,and 492.62（TD）,respectively.（3）The twin-screw reaction extrusion process was optimized to improve the melt viscoelasticity and filler dispersion uniformity of PBAT/Talc composites.The epoxy-based chain extender KL-E4370B was used for chain extension reaction,and the effects of barrel temperature,screw speed,and feeding amount on the product performance were examined.The optimal process conditions were determined through Box-Behnken response surface experimental design and data analysis:reaction temperature of 151℃,screw speed of 205rpm,and feeding amount of 5.7 kg/h.After process optimization,blown film experiments verified that film properties were improved.（4）The dispersion mixing ability of a twin-screw extruder was analyzed through POLYFLOW unit simulation in ANSYS software,and the pressure field,shear stress field,residence time,and reflux rate of polymer melt under different screw combinations were studied.The melt viscoelasticity,filler dispersion uniformity,and mechanical properties of the film were experimentally tested under different screw combinations,and the test results were compared and analyzed with the simulation results to establish the relationship between screw configuration and film performance.