Synthesis, characterization, thermal and fire retardant properties of new homo- and block copolymers of polyacrylate and epoxy resin with cyclotriphosphazene core

Abstract

New homo-and block copolymers composed of polyacrylate and epoxy resin with hexafunctional cyclotriphosphazene core were synthesized and characterized by FT-IR and 1 H-, 13 C-, and 31 P-NMR. The first homopolymer, PN-polyacry was prepared from the direct condensation of 2-hydroxyethylacrylate with acyl chloride of hexakis(4-carboxyphenoxy)cyclotriphosphazene, PN-acyl. The second homopolymer, PN-Ep, was prepared in a direct reaction of catalyzed carboxyl groups of hexakis(4-carboxyphenoxy)cyclotriphosphazene PN-COOH with epoxy resin via an oxirane ring opening re action. The block copolymer, PN-Ep/polyacry, was prepared from the partial coupling of 2-hydroxyethyl acrylate with the PN-acyl, followed by the reaction of unreacted carboxyl groups with epoxy resin. Differential scanning calorimetry (DSC) analysis of the PN-Ep/polyacry copolymer exhibited good compatibility between polyacrylate and cured epoxy resin. Thermal gravimetric analysis (TGA) revealed that the prepared polymeric systems accumulate 30-38 wt % char at elevated temperatures, compared to neat polyacrylate and cured epoxy resin, which accumulate negligible char at 700 °C. The limiting oxygen index (LOI) exhibited significant enhancement of fire retardant properties of the prepared polymeric systems. A scanning electron microscopy (SEM) morphology study revealed that PN-polyacry and PN-Ep/polyacrylate produced intumescent char residues while PN-Ep produced solid dense char with a nonporous surface.

Core-Shell Graphitic Carbon Nitride/Zinc Phytate as a Novel Efficient Flame Retardant for Fire Safety and Smoke Suppression in Epoxy Resin

“…Epoxy resin (EP) is one of the most important resins because of its excellent moldability, corrosion resistance, adhesion, mechanical and electrical properties [1,2]. It is widely used in communications, automotive industry, semiconductor device, construction and other fields [3]. However, EP consists of flammable hydrocarbon chains, resulting in thermal and toxic hazards to life health and environment during combustion [4].…”