多功能聚磷腈基阻燃剂的构建及对聚乳酸的阻燃、抗熔滴和增韧作用机制研究

The development of halogen-free flame retardant polylactic acid (PLA) composites with excellent comprehensive performance has recently emerged as one reseach focus in the area of polymer materials. This proposed project aims to address the key issue associated with the current flame retardant system that could not simultaneously solve flamability, droppability and mechanical brittleness of PLA. The project proposes to optimized molecular design on the basis of the preliminary work and synthesize a novel polyphosphazene-based multi-functional flame retardants with adjustable side groups, and to play the multiple roles of flame retardancy, cross-linking, toughening and anti-dripping in the PLA at the same time. The effects of the types of side group, each component containing ratio, and synthetic parameters on the chemical structure and composition, thermal properties, cross-linking behavior, char-forming capability and quality of residue chars of the flame retardants will be investigated, and then the aimed flame retardant with prominent performance will be synthesized.The loading-level-performance and structure-performance correlations will be clarified by examining the effect of loading levels and chemical structure and composition of as-prepared flame retardants on the flame retardancy of PLA composites. The flame retardancy and anti-dripping mechanism will be revealed by probing the evolution of the structure, composition and chemical reaction of the degradation products generated in gas and condensed phase during the thermal degradation, burning and char-forming process as well as the high-temperature crosslinking of flame retardancy of PLA and the change of melt viscosity. The project will illuminate the toughening mechanism of as-prepared flame retardants for PLA by investigating the mechanical properties, fracture morphology and crystallization behavior of flame retardancy of PLA. The theoretical and application guidelines will be provided for developing novel high-performance flame retardants and flame retardant PLA materials.

研发综合性能优异的无卤阻燃聚乳酸材料是当前高分子材料领域的研究热点。针对当前阻燃体系不能同时解决聚乳酸材料易燃、易滴落及力学脆性的关键瓶颈，本项目拟在前期基础上，优化分子设计，构建侧基可调的新型聚磷腈基多功能阻燃剂，使其在聚乳酸体系中同时发挥阻燃、抑熔滴及增韧的多重作用。研究侧基的种类、各组分含量及合成工艺等参数对阻燃剂的结构组成、热稳定性、交联行为、成炭能力和炭层质量等的影响，制备性能优异的阻燃剂。研究阻燃剂的添加量和结构组成与聚乳酸材料阻燃性能间的量效和构效关系，聚乳酸材料在热降解、燃烧和成炭过程中的气相及凝聚相产物的组成、变化及热分解过程中的化学反应，考察阻燃聚乳酸的高温自交联作用及熔体粘度变化规律，揭示阻燃剂在PLA材料中的阻燃和抗熔滴机制。考察阻燃PLA的力学性能、破裂形貌及结晶等行为，阐明阻燃剂的增韧机制。该项目的研究将为开发高性能阻燃剂及阻燃聚乳酸材料提供理论基础和技术支撑。

聚乳酸（PLA）具有优异的力学强度、良好的透明度、易加工性及可生物降解等优点，被认为是替代通用塑料的理想环保生物塑料。研发具有高性能阻燃的PLA复合材料在当前电子工程材料与火安全材料领域受到广泛的关注。针对当前阻燃体系不能同时解决聚乳酸材料易燃、易滴落及力学脆性的关键瓶颈，本项目采用分子设计构建了系列多功能聚磷腈基阻燃剂，用于制备高性能聚乳酸复合材料，建立了新型阻燃剂的结构组成与PLA复合材料性能之间的量效和构效关系，明确了该类阻燃剂在PLA复合材料中对材料的阻燃、抗熔滴和增韧的影响规律，揭示其阻燃、抗熔滴和增韧的作用机制。项目研究结果表明：1、得益于制备的磷氮多功能阻燃剂（PPE）的高效气相阻燃效果和优秀的界面相容性，添加0.5wt% PPE可使PLA复合材料获得26.1%LOI，通过UL-94 V0级别，实现机械性能全面提升。2、通过调控侧基结构组成制备出的鸟嘌呤-聚磷腈基阻燃剂，可实现PLA复合材料的增韧阻燃抗熔滴作用，当添加5wt%的PAHP时，PLA复合材料的断裂伸长率可达112.1%，获得工程满意的UL-94 V0阻燃等级，而且PLA复合材料还获得了额外的抗紫外线能力。3、通过在侧基上进行元素调控和引入自交联基团制备共取代聚磷腈基阻燃剂，可有效提高阻燃剂的抗熔滴效果，当添加5wt%PAHTAP时，PLA复合材料获得UL-94 V0阻燃等级，且其熔滴生成时间和间隔较纯PLA的熔滴生成时间和间隔分别提高57.8%和148.4%，这是因为阻燃剂在燃烧时不仅稀释可燃气体的浓度起到气相阻燃作用熄灭火焰，同时起到增加熔体黏度和提高复合材料分子量的作用。本项目研究成果可为开发新型多功能阻燃剂以及高性能聚乳酸复合材料提供理论基础和数据支撑。