【作者】 宣善勇；

【导师】 胡源；

【作者基本信息】 中国科学技术大学 ， 安全技术及工程， 2011， 博士

【摘要】 聚乳酸是一种来源于可再生农作物的完全可生物降解聚合物,其良好的力学性能和生物相容性使其成为公认的可以在一定程度上取代传统石油基聚合物,但是其燃烧熔滴现象严重等问题限制了其应用范围,因此需要对其进行阻燃处理。本文在大量文献调研的基础上,综述了聚乳酸基本性能、聚乳酸的阻燃研究及POSS和碳纳米管作为聚合物阻燃剂的研究。针对聚乳酸燃烧熔滴现象严重的问题,采用膨胀型阻燃体系作为聚乳酸的阻燃剂,制备了阻燃复合材料,研究了材料的阻燃性能和阻燃机理,并将新型膨胀阻燃技术如包裹技术和三元一体膨胀阻燃技术应用于聚乳酸的阻燃,同时将POSS和碳纳米管作为阻燃协效剂引入聚乳酸阻燃体系,研究了POSS和碳纳米管对聚乳酸热降解机理和阻燃性能的影响,并讨论了阻燃机理。本论文归纳起来分以下几个部分:1.合成了成炭剂PEPA和ODOPM并将其与MP复配组成膨胀型阻燃体系应用于聚乳酸的阻燃。研究表明MP/ODOPM可以提高聚乳酸的极限氧指数,降低聚乳酸的PHRR,并能使聚乳酸通过UL94 V0测试,其最佳配比为1:1;MP /PEPA的加入可以极大的提高聚乳酸的极限氧指数,复合材料能通过UL94 V0测试,同时复合材料燃烧时并不产生熔滴现象,PU的加入可以提高复合材料的拉伸强度和冲击强度,并且使得燃烧后形成的炭层更加致密。2.以10-(2, 5-二羟基苯基)-10-氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO-BQ)和聚磷酸铵(APP)为酸源,以异氰尿酸三缩水甘油酯(TGIC)为气源,以聚乳酸为炭源制备了膨胀型阻燃聚乳酸复合材料。研究表明膨胀型阻燃体系能够提高聚乳酸的极限氧指数,并能使得复合材料达到UL94 V0级别。MCC结果显示,膨胀型阻燃剂能够降低复合材料的PHRR,TGA结果显示,阻燃复合材料的热稳定性和热解后成炭量都比聚乳酸高。对炭渣进行分析表明,复合材料的膨胀炭层较为致密,提高了材料的火灾安全性。制备了“三元一体”膨胀型阻燃剂BTOCPM,将其应用于聚乳酸阻燃,可以明显提高聚乳酸的阻燃级别,机理研究表明BTOCPM可以促进聚乳酸的燃烧成炭。动态力学研究表明,BTOCPM与聚乳酸的相容性较好。3.为了降低阻燃剂的吸水性,提高阻燃剂与聚乳酸基体的相容性,降低材料的成本,以微胶囊包裹聚磷酸铵(PUMAPP)为酸源,三聚氰胺为气源,淀粉为炭源的膨胀阻燃体系应用于聚乳酸阻燃。膨胀阻燃聚乳酸复合材料的极限氧指数有着极大的提高,同时能够通过UL94 V0测试,并且其PHRR和THR相比纯聚乳酸都有所降低。TGA测试表明其热稳定性和热解成炭量都有所提高。TG-FTIR、RTFTIR及XPS分析可得知膨胀阻燃体系的加入可以增加不可燃挥发性气体的释放量,并且使得聚乳酸燃烧时,其表面形成致密炭层,提高了材料的火灾安全性。4.将TPOSS作为阻燃协效剂引入微胶囊包裹聚磷酸铵和三聚氰胺膨胀阻燃体系,并应用于聚乳酸阻燃。研究表明,TPOSS以纳米尺寸聚集于复合材料基体中。IFR与TPOSS在一定的比例下能够大大提高聚乳酸材料的氧指数,并能够通过UL94 V0测试,同时能够极大的降低聚乳酸的PHRR和THR,随着TPOSS添加量的增加,阻燃复合材料的成炭量增加明显,膨胀性更加明显,并且燃烧时不会出现熔融滴落现象。对RTFTIR、TG-FTIR及XPS的测试结果进行分析,得到TPOSS协效膨胀阻燃聚乳酸复合材料的阻燃机理为:在燃烧初期囊材降解、破裂,PUMAPP放出磷酸和大量不燃性气体,催化PLA降解,形成膨胀、多孔炭层;TPOSS受热氧化降解生成SiO2类物质覆盖在炭层的表面,提高炭层的热稳定性。此炭层会阻止气相和固相之间的热与质量交换,阻止内部材料的进一步燃烧,达到阻燃的目的。5.将MWNTs和POSS作为阻燃协效剂引入PEPA/MP膨胀阻燃聚乳酸体系,研究了它们对复合材料的热降解性能和阻燃性能的影响。惰性气氛中和空气气氛中,MWNTs的引入可以提高复合材料在高温区的热稳定性和成炭量,MWNTs在复合材料基体中主要作用是形成了网状结构阻止了热解气体的释放;MCC和LOI结果表明,当MWNTs的添加量达到一定程度时可以明显提高复合材料的LOI,PHRR也有所降低。空气气氛下,MWNTs的加入可以提高复合材料的氧指数和成炭量,但是对热氧化降解机理没有明显的影响。惰性气氛下,TPOSS在较低的温度下升华和裂解,导致复合材料的起始热降解温度提前,对复合材料高温下的热稳定性和成炭量没有明显影响;TG-FTIR结果表明,TPOSS可以降低复合材料的二氧化碳和环状低聚物的释放,提高一氧化碳的释放;空气气氛下,TPOSS改变了复合材料的热氧化降解机理,提高了复合材料的热稳定性和成炭量。TPOSS加入后,可以提高复合材料的极限氧指数,并能通过UL94 V0测试。炭渣测试表明,TPOSS的加入可以提高复合材料的粘度,阻止气体的逸出,同时TPOSS在受热氧化后形成了二氧化硅类物质覆盖在炭层表面,使得炭层热稳定性提高,因此复合材料的热稳定性能提高。更多还原

【Abstract】 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.更多还原