Preparation and Mechanisms of High-Performance PET Bead Foams
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(scCO2)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 scCO2 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 100.8 μm,a cell density of 1.91×106 cells/cm3,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.
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