Use of boron oxide and boric acid to improve flame retardancy of an organophosphorus compound in neat and fiber reinforced polyamide-6

The aim of this study was to investigate the usability of boron oxide and boric acid to enhance flame retardancy of (aluminum diethyl phosphinate)-type organophosphorus compound in polyamide-6 and its 15 wt% of short (glass fiber)-reinforced composite. Materials were compounded by melt-mixing method via a twin-screw extruder, and the specimens for testing and analyses were shaped by injection and compression-molding. For the neat polyamide-6 specimens, mass loss cone calorimetry analyses indicated that replacement of a certain amount of aluminum diethyl phosphinate with boron oxide or boric acid could result in significant improvements in many flame-retardancy parameters. For instance, the suppression in peak heat release rate value of polyamide-6 could be as much as 84% or 86% for boron oxide and boric acid, respectively, whereas it was only 32% when aluminum diethyl phosphinate was used alone. Char microscopy, thermogravimetric analyses, X-ray diffraction, and evolved gas analyses revealed that the main contribution of boron oxide and boric acid to the barrier mechanism of aluminum diethyl phosphinate was the formation of additional glassy boron oxide layers and boron phosphate layers. J. VINYL ADDIT. TECHNOL., 22:300-310, 2016. (c) 2014 Society of Plastics Engineer