弹性体共混改性聚乳酸(PLA)高韧性共混物研究进展

Research Progress of Elastomer Blended Modified Poly(Lactic Acid) (PLA) High Toughness Blends

聚乳酸(PLA)是最有前景的生物基可降解材料之一,其优异的力学性能、良好的可塑性以及生物相容性使其在包装、服装和医药领域有巨大的应用潜力,但PLA固有的脆性和低的冲击韧性限制了它的应用范围。近十几年来,广大学者对聚乳酸的增韧改性进行了大量研究,主要改性方法有复合、共聚、增塑和共混。复合改性是指向PLA中加入纤维、改性碳纳米管(MWCHNTs)、壳聚糖(Ch)、改性二氧化钛(TiO 2)等填料,填料与PLA形成一定的物理交联,具有补强增韧的作用,但填料与基体间的粘附与分散是有待解决的难点。共聚改性是指在PLA链上引入聚乙二醇(PEG)、聚己内酯(PCL)、甲基丙烯酸缩水甘油酯(GMA)、聚蓖麻油(PCO)等柔性分子链,PLA分子链规整度和结晶度下降,韧性改善显著,但高额的成本、严重的污染和复杂的反应流程无法满足实际应用的需求。增塑改性是指在PLA中加入柠檬酸酯、甘油基酯、聚乙二醇、乳酸及乳酸酯等小分子物质,增强PLA分子链的运动能力,断裂伸长率大幅提升,但增塑剂易迁移这一问题仍有待解决。共混改性是将PLA与橡胶粒子或热塑性弹性体(聚氨酯类热塑性弹性体(TPU)、聚烯烃类热塑性弹性体、聚酰胺类热塑性弹性体(TPEA)等)等柔性高分子共混,利用橡胶或弹性体组分在剪切脱粘或发生形变时吸收能量,使PLA的韧性大幅提升,其中,热塑性弹性体具有比橡胶粒子更好的加工性,对PLA的增韧效果也更好,是PLA增韧改性研究的焦点。本文归纳了石油基热塑性弹性体与生物基/可降解弹性体增韧改性PLA的研究进展,分别从物理共混和反应性共混两方面介绍了增韧改性的原理与方法,分析了共混物相形貌和界面缠结作用力的变化对共混物性能的影响,反应性共混和动态硫化工艺有利于在共混过程中实现原位增容,是制备高韧性PLA/弹性体共混物的有效途径;详细介绍了生物基/生物可降解弹性体增韧PLA制备高韧性全生物基/生物可降解PLA共混物的主要方法和渠道,生物基/可降解弹性体是弹性体增韧PLA的一个新兴方向,具有重要的研究价值。

Poly(lactic acid)(PLA)is one of the most promising bio-based degradable materials.Its excellent mechanical properties,good plasticity and biocompatibility make it have great application potential in packaging,clothing and medicine,but PLA inherent brittleness and low impact toughness limit its range of applications.In the past ten years,many scholars have carried out a lot of research on the toughening modification of PLA.The main modification methods are compounding,copolymerization,plasticizing and blending.Composite modification refers to the addition of fibers such as fibers,modified carbon nanotubes(MWCHNTs),chitosan(Ch),and modified titanium dioxide(TiO 2)to the PLA.The fillers form a physical crosslink with PLA to enhance strength and toughness,but the adhesion and dispersion between the filler and the matrix is a difficult problem to be solved.Copolymerization modification refers to the introduction of flexible molecular chains such as polyethylene glycol(PEG),polycaprolactone(PCL),glycidyl methacrylate(GMA),and polyricin oil(PCO)onto the PLA chain these copolymers reduce the molecular chain regularity and crystallinity of the PLA,the toughness is improved significantly,but the high cost,serious pollution and complexity reaction process cannot meet the needs of the actual application.Plasticization modification refers to the addition of small molecular substances such as citrate,glyceryl ester,polyethylene glycol(PEG),lactic acid and lactate to PLA,which can enhance the mobility of PLA molecular chains,and the elongation at break is greatly increased,but the phenomenon of plasticizer migration is still to be resolved.Blending modification is to blend PLA with flexible polymers such as rubber particles or thermoplastic elastomers.When the flexible polymer component absorbs energy during shear debonding or deformation,the toughness of PLA is greatly improved.Among them,the thermoplastic elastomer has better processability than rubber particles,and the toughening effect on PLA is better,which is the focus of PLA toughening modification research.In this paper,the research progress of petroleum-based thermoplastic elastomers and bio-based/degradable elastomers toughened modified PLA is summarized.The principles and methods of toughening modification are introduced from the aspects of physical blending and reactive blending.The effects of the morphology of the blend phase and the interfacial entanglement on the properties of the blend were analyzed.Reactive blending and dynamic vulcanization process are beneficial to in-situ compatibilization in the blending process and are an effective way to prepare high toughness PLA/elastomer blends.The main methods and channels for bio-based/biodegradable elastomer toughened PLA to prepare high-toughness bio-based/biodegradable PLA blends are described in detail.Bio-based/degradable elastomers are an emerging direction for elastomer-toughened PLA and have important research value.