Electron-Beam Radiation Crosslinkable and Compatibilized PA11/PA12/LDPE Blends with Good Barrier Properties and Improved Heat Resistance for Cable Sheathing Application

摘要

This study is inclined toward polyamide/low-density polyethylene (PA/LDPE) blends compatibilized by ethylene/acrylic acid copolymer (EAA) and crosslinkable with electron-beam (EB) radiation. The PA/LDPE blends are intended to be co-extruded to form the cable outer sheath along with the EB radiation crosslinkable inner insulation layer composed of flame retardant, halogen-free polyolefin; and subsequently both the insulation and the sheath are crosslinked with EB radiation. The blend component PA was a mixture of a plasticized PA11 and a flame retardant, halogen-free PA12. The chemical reaction between the carboxyl group of EAA and the amine end group of PA could not be confirmed by rheological measurements on the variations of compounding torque and melt viscosity. The reaction was suspected to occur from the disappearance of the characteristic peak of EAA at 1704.3 cm~(-1) in the Fourier transform infrared (FTIR) spectra. A polyfunctional monomer trimethylolpropane trimethacrylate (TMPTMA) and an additional hybrid antioxidant system were incorporated into the PA/LDPE blends to be crosslinked by EB radiation, leading to an improvement in high temperature performance. The PA/LDPE/EAA blends were proved to qualify good barrier properties against permeation of mineral oil and fuel. The scanning electron microscopy (SEM) technique revealed that the morphologies of the PA/LDPE blends in the presence and the absence of EAA were fairly different, indicating that a small amount of EAA could function as a compatibilizer. The impact and SEM tests also showed that the appropriate radiation treatment can assist compatibilization of PA and LDPE. The EB radiation plus the addition of the reactive compatibilizer yielded the best compatibilization effect in terms of morphology and impact strength.