Molded Foam Study of Poly(Adipic Acid)-Butylene Terephthalate/Thermoplastic Starch Blending System
As a biodegradable and environmentally friendly plastic,polybutylene adipate terephthalate(PBAT)has excellent ductility,flexibility,and film-forming properties,and has achieved rapid application development under the promotion of national policies.However,it has the problems of low melt strength and weak crystallization ability.During the physical foaming process,the foam cell structure is prone to rupture and collapse,leading to matrix shrinkage.Therefore,the foaming conditions and equipment requirements are relatively strict.In addition,the relatively high cost of PBAT raw materials also limits its commercial development.Therefore,in this paper,the low-cost and anti shrinkage PBAT/TPS foam was prepared by supercritical CO2 molding foaming method using a convenient method of melt blending of PBAT and thermoplastic starch(TPS).At the same time,the thermal behavior and rheological behavior of PBAT/TPS blends were studied,and the effects of different TPS content on the foaming behavior and shrinkage recovery behavior of PBAT/TPS foam were analyzed.The research results indicate that as the TPS content increases from 10 wt%to 40 wt%,TPS gradually transforms from a dispersed phase to a continuous phase in the PBAT/TPS blend system.An increase in TPS content will cause the crystallization temperature of PBAT/TPS blend system to increase from 40℃to 74.5℃,the platform modulus to increase by about 2 orders of magnitude,and the linear viscoelastic zone will shift towards low strain direction,making the process of bubble growth more likely to occur.In addition,research has found that the addition of TPS can improve the anti shrinkage ability of PBAT/TPS blend system,which is beneficial for the reasonable control of preparation costs.When TPS content was 20 wt%,the shrinkage rate of PBAT/TPS foam was only 0.017 times·min-1,and the expansion rate after stabilization was 4.7 times.Compared to pure PBAT,the raw material cost of the blend system is reduced by about 16%.This study provides a widely applicable method for large-scale commercial production of biodegradable polyester foam with anti shrinkage.
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