Thermo-oxidative degradation behaviors of expandable graphite-based intumescent halogen-free flame retardant LLDPE blends

The thermo-oxidative degradation behaviors of expandable graphite (EG)-base d intumescent halogen-free flame retardant LLDPE blends under different the rmo-oxidation conditions have been studied by real time Fourier transform i nfrared (FTIR) spectroscopy or FTIR photoacoustic spectroscopy (FTIR-PAS), X-ray photoelectron spectroscopy (XPS), and wide-angle X-ray diffraction (W AXD). The real time FTIR results show that the pyrolysis of LLDPE at high t emperature leads to the breakdown of PE chains and the formation of various kinds of thermal oxidation products. The addition of EG can improve the st ability of thermo-oxidative degradation effectively. The FTIR-PAS and XPS d ata show that the thermo-oxidative degradation of LLDPE decreases remarkabl y with the increase of EG concentration and/or its synergists and increases dramatically with the increases of pyrolytic temperature and thermal degra dation time. The thermo-oxidative degradation products have been identified as various kinds of carbonyl compounds, such as ethers, esters, ketone or carboxyl products. The WAXD measurements demonstrate that the crystalline s tructures of LLDPE/EG or LLDPE/EG/HFFR blends after the thermo-oxidation de gradation have been destroyed partly or totally dependent on the pyrolytic temperature and thermal degradation time. The changes of crystalline struct ure in the LLDPE/EG/HFFR blends are due to the breakdown of LLDPE chains an d a series of reaction products with FR additives. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.