Enhanced fire-retardancy of poly(ethylene vinyl acetate) electrical cable coatings containing microencapsulated ammonium polyphosphate as intumescent flame retardant

Abstract

There is a need to improve and maintain the protection function of ethylene-vinyl acetate copolymer (EVA) cable materials from ageing degradation to avoid fire hazards and extend their service lives. Here, a flame retardant, branched silane precursor, pentaerythritol triacrylate-(3-aminopropyl) triethoxysilane (PETA-APTS), containing a vinyl group and hydrolysable silane structure was successfully synthesized and characterized, and it was used to prepare microencapsulated ammonium polyphosphate (MCAPP) particles with tetraethoxy silane via a successive Stöber method, which aimed to immobilize the MCAPP into the EVA matrix through a crosslinking treatment. Damp-heat ageing tests (85 °C, 85% R.H.) were carried out on the EVA/APP (EVA-1 system) and EVA/MCAPP (EVA-2 system) to explore the protective effect of the microencapsulation method over 6 weeks. Digital photos, SEM images, gel-content tests and X-ray photoelectron spectroscopy results showed that the MCAPP particles had excellent compatibility with the EVA matrix and did not migrate or eroded with water vapor at 85 °C. Remarkably, this phenomenon led to great improvements in the mechanical properties, electrical insulation performance and fire safety for the EVA-2 system compared to the EVA-1 system. This investigation provided a formulation for the industrial application of the EVA/IFR cable as an insulated material with excellent long-term stability and fire safety.