聚乳酸阻燃增韧双功能离聚物助剂的设计合成与应用研究

As a biodegradable thermoplastic polyester and a promising alternative material to petro-derived polymers, polylactide (PLA) have been the focus of attention for years. However, the poor fire-resistance and brittle nature of PLA restricts its application and development. Up to now, the study about simultaneously improving the flame retardancy and tougheness of polylactide by added only one additive is very rare, although many studies have been done about the modification of PLA. In this work, a new type dual-functional ionomer additives which be used in the flame retardancy and toughening modification of PLA will be synthesized. These ionomer additives contain two segments: one segment is the polyester segment, which not only can improve the compatibility between ionomers and PLA matrix, but also play a role in toughening PLA; the other one is ionic enriched segment, which can spontaneously form inter- and intra-molecular ionic aggregates in PLA, thus to serve as physical crosslinking points to accomplish the excellent anti-dripping performance of PLA matrix. Besides, due to a variety of phosphoric acid with flame retardancy can be introduced through acid-base neutralization reaction with tertiary amine in the synthesis process of ionomer additives, the flame retardancy of the modified PLA will be further improved. Through these studies, the corresponding theoretical model and its possible mechanism will be put forward. This research will provide not only novel preparation strategy for this research area, but also a theoretical fundament for potential application of this kind of additives.

聚乳酸是一种重要的可生物降解高分子材料，但易燃以及脆性大等缺点，使其应用领域受到很大的限制。目前，分别实现聚乳酸阻燃或者增韧的改性助剂有很多，但在聚乳酸中简单的同时加入这两种改性助剂，往往并不能同时实现基材的有效阻燃和增韧。因此，本项目将通过分子设计，拟合成具有阻燃增韧双功能的离聚物助剂，然后通过简易的物理共混则可同时实现聚乳酸的阻燃增韧。该离聚物助剂主要由非极性的聚酯主链和离子化的共聚单体两部分组成。聚酯链段的作用体现在对基材的增韧增塑方面。离子化共聚单体的作用不仅体现在其合成过程中，利用叔胺的弱碱性，通过酸碱中和反应引入各种具有阻燃作用的含磷弱酸，提高基材的阻燃性；还体现在最终形成的离子聚集体，增加分子链间的缠绕，增大燃烧时的熔体黏度，实现基材的抗熔滴。通过系统研究助剂分子结构、聚集形貌与离聚物对基材宏观阻燃增韧效果之间的联系，提出阻燃增韧的机理，为材料的阻燃增韧提供新的研究思路。

聚乳酸（PLA）是一种重要的可生物降解高分子材料，但易燃以及脆性大等缺点，使其应用领域受到很大的限制。目前，分别实现聚乳酸阻燃或者增韧的改性助剂有很多，但在聚乳酸中简单的同时加入这两种改性助剂，往往并不能同时实现基材的有效阻燃和增韧。因此，本项目利用离聚物同时具有非极性聚合物主链与离子基团的这种特殊分子结构，分别设计合成了对PLA有阻燃增韧改性作用的线性以及支化双功能离聚物助剂。通过少量添加这种大分子离聚物助剂，就能同时实现聚乳酸的高效阻燃增韧改性。另外，进一步研究了离聚物助剂能够高效阻燃、增韧改性聚乳酸的机理，为后续PLA的多功能化改性提供新的研究思路。在此基础上，不断优化离子液体（离子盐）的结构及组成元素，合成了具有抗菌、增韧、阻燃多功能化的离聚物助剂，并将其用于了聚乳酸的改性研究。相比于传统的加工助剂，离聚物助剂的优势主要体现在用于聚乳酸改性时，一种加工助剂即可实现多功能化改性，添加量少，改性效果好，具有一定推广的价值。通过本项目的开展，采用相同的分子设计思路，可以进一步合成出具有其他多种功能化的离聚物助剂，不仅可以为更多聚酯材料的改性研究提供借鉴和指导，还可以很大程度上拓展离聚物助剂的实际应用领域。