Synthesis of a hyperbranched poly(phosphamide ester) oligomer and its high-effective flame retardancy and accelerated nucleation effect in polylactide composites

Abstract

In this article, a hyperbranched poly(phosphamide ester) oligomer HBPE was prepared via A3 + BB′ method. FTIR spectrum, 1H and 31P NMR spectrum and GPC were utilized to characterize HBPE. Then HBPE was melt blended with PLA to fabricate flame retardant PLA composites. The integrated flame retardant property of PLA composites was investigated by LOI, UL-94, pyrolysis combustion flow calorimeter test (PCFC) and cone calorimeter test (CCT). The thermal stability of PLA composites was investigated by TGA, weight loss difference analysis and integral procedural decomposition temperature (IPDT). Results showed that PLA composite with only 2 wt% HBPE exhibited excellent flame retardancy (LOI = 33% and UL-94 V-0 rating) and 10 wt% HBPE imparted PLA composites largely increased LOI value of 43%. The incorporation of 10 wt% HBPE increased CO production rate (COP) and prolonged time to ignition (TTI) in CCT. Furthermore the thermal stability of PLA composites was enhanced from IPDT analysis. Meanwhile, DSC analysis of PLA composites showed Tg of PLA composites decreased slightly with the addition of HBPE, which indicated the limited plasticizing ability of HBPE in PLA composites. Finally, the accelerated nucleation effect was also detected in PLA composites using POM observation. Results showed HBPE was a high-effective flame retardant of PLA, exhibiting good nucleating property and limited plasticizing ability in PLA composites.