高性能PET珠粒泡沫的制备及机理

Preparation and Mechanisms of High-Performance PET Bead Foams

聚对苯二甲酸乙二醇酯(PET)高温熔体强度低,难以通过超临界二氧化碳(scCO_(2))发泡技术制备高强度、高膨胀率的珠粒泡沫材料。本文建立了一种基于原位熔体增强的发泡新技术,利用聚对苯二甲酸丁二醇酯(PBT)有效负载扩链剂均苯四甲酸二酐(PMDA)得到扩链剂负载母粒(PMDA-MB)。通过PMDA-MB与PET的共混挤出制备了改性PET,有效地延长并支化PET分子链,大幅度地提升了熔体黏度,有效地改善了PET的发泡性能。进一步通过scCO_(2)珠粒发泡技术制备了具有优异的泡孔结构和高膨胀率的PET泡沫材料。结果表明,当PMDA-MB的质量分数为3%、发泡温度为244℃、发泡压力为25 MPa时,所得PET泡沫平均泡孔尺寸为100.8μm,泡孔密度1.91×10^(6)个/cm^(3),膨胀率达15.2,而且该PET珠粒泡沫材料的力学性能优良,拉伸强度达2.54 MPa,压缩强度达4.08 MPa。

Poly(ethylene terephthalate)(PET)exhibits low melt strength at high temperature,which makes it difficult to produce high-strength and high-expansion bead foam parts through supercritical carbon dioxide(scCO_(2))foaming technology.This paper established a novel foaming strategy based on in-situ melt enhancement.Poly(butylene terephthalate)(PBT)was effectively utilized to load the chain extender[(pyromellitic dianhydride(PMDA)],obtaining a chain-extender-loaded masterbatch(PMDA-MB).The modified PET was prepared by blending and extruding PMDA-MB with PET,which effectively extended and branched the PET molecular chains,and greatly improved the melt viscosity and the foaming properties of PET.Consequently,the PET foam materials with good cell structures and high expansion ratios were prepared via the scCO_(2)bead foaming technology.The results show that when the mass fraction of PMDA-MB is 3%,the foaming temperature is 244℃,and the foaming pressure is 25 MPa,the obtained PET foam exhibits an average cell size of 100.8μm,a cell density of 1.91×10^(6)cells/cm^(3),and an expansion ratio of 15.2.This PET bead foam exhibits good mechanical properties,with a tensile strength of 2.54 MPa and a compressive strength of 4.08 MPa.