PBAT/TPS共混体系模压发泡制备工艺、性能及成本研究

Molded Foam Study of Poly（Adipic Acid）-Butylene Terephthalate/Thermoplastic Starch Blending System

摘要:

聚己二酸-对苯二甲酸丁二酯（PBAT）作为一种可生物降解的环保塑料，具有优异的延展性、柔韧性和成膜性能等特性，并在国家政策推动下其应用得到迅猛的发展。然而，该材料存在熔体强度低、结晶能力弱的问题，在物理发泡过程中泡孔结构易破裂坍缩，进而导致基体收缩，因此对其发泡条件和设备要求较为苛刻。此外，PBAT原材料相对高昂的成本，也限制了其商业化发展。为此，利用便捷方法将PBAT与热塑性淀粉（TPS）熔融共混，采用超临界CO₂模压发泡法制备出低成本、抗收缩的PBAT/TPS泡沫。同时，研究了PBAT/TPS共混体系的热行为、流变行为，分析了不同TPS含量对PBAT/TPS泡沫的发泡行为和收缩恢复行为的影响，并针对多种典型聚合物进行成本核算比对。研究结果表明，随着TPS质量分数从10%增加至40%，TPS在PBAT/TPS共混体系中从分散相逐渐转变为连续相，TPS含量增加会导致PBAT/TPS共混体系结晶温度从40 ℃升高至74.5 ℃，平台模量增加约2个数量级，且线性黏弹区向低应变方向偏移，泡孔生长行为更容易产生。另外，TPS的加入能够提高PBAT/TPS共混体系的抗收缩能力，有利于制备成本的合理控制。当TPS的质量分数为20%时，PBAT/TPS共混体系泡沫收缩速率仅为0.017 倍?min^-1，稳定后膨胀倍率为4.7倍；相较于纯PBAT，共混体系的原料成本降低约16%。该研究为大规模商业化生产具有抗收缩的可生物降解聚酯泡沫塑料，提供了一种广泛适用的方法。

Abstract:

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.