Novel phosphorus‐nitrogen‐silicon copolymers with double‐decker silsesquioxane in the main chain and their flame retardancy application in PC/ABS

SummaryTwo novel phosphorus‐nitrogen‐silicon copolymers (DDSQ‐N‐P‐yne and DDSQ‐N‐P‐ene) were synthesized by hydrosilylation reaction with DDSQ and DOPO derivatives. DOPO derivatives with different end groups were designed and synthesized to compare the flame retardancy and compatibility of phosphorus‐nitrogen‐silicon copolymers by different linkers between DDSQ and DOPO derivatives. The synthesized copolymers have been evidenced by1H,29Si nuclear magnetic resonance, and gel permeation chromatography and then introduced into polycarbonate (PC)/acrylonitrile butadiene styrene (ABS) alloy to study their flame retardancy and explore whether they exhibit a synergistic effect on the flame retardancy. The flame‐retardant properties of DDSQ‐N‐P‐yne (or ene) systems as well as the morphology were investigated in detail by using limiting oxygen index, thermogravimetric analysis, UL‐94, microcalorimeter, energy dispersive X‐ray, and scanning electron microscopy, respectively. When DDSQ‐N‐P‐yne (or ene) content is 10 wt%, the composites of PC/ABS are identified to be very effective according to limiting oxygen index, UL‐94, and microcalorimeter. The microstructures of the char were investigated by scanning electron microscopy, and the results indicated a tight and compact graphitized layer shaped, which plays an important role in improving the excellent thermal stability and flame retardancy of PC/ABS alloy.