Surfactant modified zinc borate synthesis and its effect on the properties of PET

Zinc borate was prepared from the reaction of zinc oxide and boric acid in the absence or presence of cumene terminated poly(styrene-co-maleic anhydride), PSMA, added as a surfactant at varying concentrations (0.1–1 wt.% of water) to the reaction medium to investigate its effect on the growth and agglomeration of particles during reaction. Synthesized zinc borates were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) in comparison to unmodified zinc borate. The results revealed that zinc borate (molecular formula 2ZnO·3B2O3·3H2O) formed as irregular platelets. The product retained its hydration water up to 300 °C. Surface modified zinc borates, together with boron phosphate, were also employed as a flame retardant for poly(ethylene terephthalate), PET. The flame retardancy of the composites was determined by the limiting oxygen index (LOI) test. Smoke emission during fire, in terms of light transmittance, was also measured. The addition of 3% boron phosphate and 2% PSMA modified zinc borate increased the LOI value of composite materials to 26% from 22.5% of neat PET. Impact strength for the same PET based composite was increased to 11.4 kJ/m2 from 9.6 kJ/m2 of neat PET.