Study On The Preparation, Properties And Flame Retardant Mechanism Of Intumescent Flame Retardant Polylactide

Polylactide (PLA) is a biodegradable polymer derived from renewable agricultural products. The excellent mechanical and biocompatibility properties have made polylactide replace polyolefins to some extent. However, the poor fire resistance, especially the dripping tendency during the combustion limited the application of polylactide, so modification for flame retardancy is necessary. Based on the investigation of a large amount of literatures about the properties, the flame retardant development of polylactide and the use of carbon nanotubes and POSS on the flame retardant study of polymers, in this dissertation, intumescent flame retardant (IFR) have been used to impart PLA with flame retardancy, the flame properties and mechanism have been studied. New intumescent technology such microcapsulation and new intumescent flame retardant have been used to flame resistant of PLA study. In addition, Trisilanolisobutyl-POSS (TPOSS) and multi-walled carbon nanotubes (MWNTs) have been used, the synergistic effect on the thermal properties and flame retardancy of PLA/IFR composites have been studied.This dissertation is composed of six parts:1. Charring agents PEPA and ODOPM have been prepared the combination of charring agents and MP have been used as intumescent flame retardants for PLA. From the results of LOI, UL94 test, it can be found that flame retardant PLA composite with the suitable content of MP and ODOPM has a better flame retardant properties and a higher fire safety. PLA/MP/PEPA has a high LOI value and passes the UL94 V0 test, no drip has been seen during the combustion, the addition of PU can improve the impact strength and tensile strength of PLA/MP/PEPA composites, more stable char has been seen after combustion with the PU.2. PLA/IFR composites which the acid source is DOPO-BQ, the gas source is TGIC and the carbon source is PLA have been prepared. By the addition of IFR, higher LOI value has been achieved; UL94 V0 rate has been reached; PHRR has been reduced compared with pure polylactide. TGA results show that PLA/IFR composites have higher thermal stability and char production. The analysis of the char after combustion shows that more impact of char has achieved which can improve the fire safety of the material. New IFR BTOCPM which combined with acid source, gas source and carbon source has been synthesized. High flame retardancy has been achieved by the addition of BTOCPM. Dynamic mechanical analysis shows that compatibility of BTOCPM and polylactide is well.3. In order to reduce the water absorption of the flame retardant; improve the compatibility of the flame retardant and polylactide; reduce the cost of material, microencapsulated ammonium polyphosphate (PUMAPP) has been used as acid source, melamine (MA) has been used as gas source and starch has been used as carbon source to unit a IFR system, the PLA/IFR composites have been prepared. LOI, UL94, MCC and TGA results show that PLA/IFR has high thermal stability and flame retardancy. TG-FTIR, RTFTIR and XPS results show that more non-flammable gas has been released and more stable char has been formed during the combustion of the material, which improve the fire safety of polylactide.4. TPOSS has been introduced to IFR system composed with PUMAPP and MA as synergistic agent. PLA/IFR/TPOSS composites have been prepared. SEM shows that nanoscale TPOSS particles are well dispersed in PLA/IFR matrix. LOI, UL94 MCC and TGA results show that the addition of TPOSS can enhance the thermal stability and flame retardancy of PLA/IFR composites. TG-FTIR, RTFTIR and XPS results reveal that the flame retardant mechanism of PLA/IFR/TPOSS: early during the combustion, PUMAPP release of phosphoric acid and a large number of non-flammable gas, catalytic PLA degradation, expanded, porous carbon layer has been formed; SiO2 substances generated by thermal degradation of TPOSS covering the surface of carbon layers to improve thermal stability.5. The effect of MWNTs and TPOSS on the thermal stability and flame retardancy of PLA/MP/PEPA composites has been studied. The net-work of MWNTs with the suitable content has been generated which can improve the thermal stability and flame retardancy of PLA/MP/PEPA composites in inert and air atmosphere. In inert atmosphere, sublimation of TPOSS has been observed, which reduced the thermal stability of PLA/MP/PEPA composites; more flammable gas has been released which reduced the flame retardancy of PLA/MP/PEPA composites. In air atmosphere, more stable compounds have been generated during the thermal degradation of hybrids, the addition of TPOSS can enhance the viscosity of the char during the combustion of hybrids which can prevent the release of gas, the improving intumescent of hybrids has been observed, thermal stability and flame retardancy has been improved by the addition of TPOSS in air atmosphere.