Good extrusion foaming performance of long‐chain branched PET induced by its enhanced crystallization property

Abstract

Poly(ethylene terephthalate) (PET) was modified by regulating different contents of branching agent epoxy‐based multifunctional oligomer and chain extender pyromellitic dianhydride in reactive extrusion process. The modified PET with better long‐chain branched (LCB) structure boosted its rheological properties, and its enhancement of melt viscoelasticity resulted in excellent foamability in molten‐state foaming process using supercritical CO2 as blowing agent. More importantly, the branched structures acted as crystal sites to accelerate the crystallization kinetic of LCB PET whether under atmospheric pressure or high‐pressure CO2. The shear and elongation flow inside die further quickly induced the crystallization of LCB PET. The rapidly generated fine crystals could both introduce heterogeneous cell nucleation and suppress CO2 escape, so the cell morphology of LCB PET in continuous extrusion foaming process exhibited a three‐fold increase in cell density and smaller uniform cell size with respect to those of other foam‐grade PET with long‐chain structure.

Analysis of Bubble Growth in Supercritical CO2 Extrusion Foaming Polyethylene Terephthalate Process Based on Dynamic Flow Simulation

“…Moreover, Figure 13 b shows that the predicted values of the bubble growth model were larger than the experimental values. Actually, the outer surface of the foamed extrudates would undergo a cooling process and the rate of cell solidification would be faster compared to the core of the foamed extrudates [ 50 ]. The bubble growth model was based on the isothermal process.…”

Molecular structure and rheological properties of a poly(ethylene terephthalate) modified by two different chain extenders

“…The high interest in modifying the molecular structure of polyesters by reactive processing with chain extenders has been reflected by the scientific 1–21 and patent literature 22‐25 during recent years. This is mainly due to novel commercially available chain extenders, or chain extender masterbatches, and to the rising attention to biodegradable polyesters.…”

Viscosity improvement of recycled poly (ethylene terephthalate) from waste bottles by adding antioxidants and chain-extender

“…The so-called "PET bottles" [3]. PET bottles are light weight bottles, which have high durability, toughness, good impact and pressure resistance, high gas permeability resistance, heat resistance and flame retardant [4,5,6]. PET is not a type of plastic that is easy to decompose.…”

“…Presently, the recycled PET can be used to produce various type of products. Such as fibers, fabric, packaging, clothing, carpet, suitcase, and core materials [6].…”

“…To fix this problem, the rPET properties can be improved to better support the extrusion process. For example, by increasing the melted strength by increasing the molecular weight and the modifying the molecular structure into a branching structure by adding chain extenders [2,4,6,12,13].…”