聚乳酸/聚丙烯、聚乳酸/OBC反应共混物的相结构形成机理与调控

There are some crucially important issues for the developing of the blending polymer materials with high quality and excellent performances, including the theoretical and/or technological fundamentals like the formation mechanism and rules of phase morphology and structure, manipulation of dispersed-phase structure. In this project, two reactive blending systems, poly(lactic acid)/polypropylene (PLA/PP) and PLA/olefin block copolymer (OBC), will be investigated extensively, to offer the new understandings on the challenges mentioned above. Some interesting dispersed phase structures can be easily available in these two blends, such as shell-core structure, subinclusions in shell-core droplet, fiber-like structure, and a substructure that was rarely found in the past works, is temporarily named as separately packed objects. However, the in-situ grafted copolymers, formed during the reactive process, is to prevent the understanding in the formation mechanism of phase structures. We will reveal the natural function of in-situ grafted copolymer, based on three issues: composition polydispersity, asymmetric interaction between different constituent pairs, and thermodynamic stability of phase structure. As to the methodology of manipulation of phase structure, we are interesting on the critical conditions, which are favorable for the generation of nanostructured types with good thermal stability. For this goal, we suggest a new idea that depressed the asymmetry between different interactions to facile the formation of such special phase structures. The theoretical understandings obtained from this project are very meaningful for the R&D of new products based on the blends with PLA constituent. So, the huge vales in this project for both of academic and application areas can be expected.

对于发展高品质、性能优异的共混物材料，深入理解形态结构形成机理与演变规律、对相结构进行有效控制等理论及技术上的关键科学问题至关重要。本项目中，申请人以聚乳酸/聚丙烯、聚乳酸/OBC两种反应共混物为研究对象，期望对这些关键问题能有新的认识。在这两种共混物中能较容易形成几种有趣的相结构，比如核-壳、含包容物的核-壳、纤维化，以及比较少见的分隔包裹次级结构。但共混过程中原位形成的接枝共聚物对阐述结构形成机理造成了困难。我们拟从组分的多分散性、组分间相互作用非对称性、以及相结构的热力学稳定性这三个方面对接枝共聚物的作用本质进行深入探讨。在相结构调控方法学方面，我们重点探索利于具有纳米级尺度且热力学稳定的相结构形成的关键因素，提出通过抑制组分间相互作用的非对称性来获得这种目标结构的新观点。本项目的研究结果可用于指导进行基于聚乳酸共混物的新产品开发与推广，在理论研究与实际应用两方面都显示出巨大的价值。

发展新型的聚乳酸/聚烯烃共混物对于缓解高分子材料的“白色污染”问题具有重要的现实意义。我们选择PLA/PP、PLA/OBC、PLA/HDPE这几类典型不相容共混物为研究对象，探索反应性共混与热退火后处理过程中相形态的形成及演变规律，系统考察了组成比、粘度比、组分相容性、加工温度、共混顺序、混合时间等对形态结构的影响；通过热力学及动力学调控手段，在共混物中形成核-壳、Subinclusions、Salami、微纤、双连续等相结构；通过调整相形态类型、相结构完善程度、界面层厚度及分散相尺寸来影响共混物力学性能，构建相形态与宏观性能的关系。本项目的重要研究结果及科学发现包括：（1）对于PLA/PP共混物，可通过微注加工获得理想的原位微纤化结构，克服了传统微纤化技术需要两组分熔点差别大的限制，是简单、高效的力学增强新方法；加入过氧化物引发剂促使PP和增容剂发生化学反应，改变原来组分间的非对称相互作用，促进增容剂在界面处分布，是增强界面改性效果的有效方法。（2）在PLA/OBC共混体系上，利用动力学手段，可调节原位接枝反应发生的时机、位置和反应程度，改变接枝共聚物的分布、分散行为，抑制了非对称相互作用的不利影响，为精确调控分散相次级结构提供了更多可行性，并为熔融共混获得Salami这种特殊相结构提供了新思路；将动力学亚稳态向热力学稳定态转变，优化了界面作用与相结构，在弹性体含量很低的情况下获得超高韧性，为开发刚-韧平衡的PLA材料提供有益参考。（3）引入高速剪切场能够改善不相容共混物PLA/PP、PLA/OBC的相容性，是简单、直接的物理增容方法，丰富了聚烯烃/聚乳酸共混物的增容改性手段。（4）在PLA/HDPE初始双连续结构的基础上，不断加入增容剂引发了相反转，形成含量较少的增容剂作为连续相而PLA和HDPE为分散相的特殊相结构，此时共混物具有超高的韧性并保持较高模量，这对于开发高性能聚乳酸/聚乙烯包装新材料具有重要的参考价值。