兼具韧性和生物降解性双梯度功能的大尺寸聚乳酸/聚己内酯材料的制备及性能研究

As two typical biodegradable polymers, poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) have been intensively studied and widely used for many applications. The glassy PLA with much slower degradation rate shows better tensile strength, whereas the rubbery PCL with high degradation rate exhibits better toughness. Thus, the blending of these two materials is an effective method to obtain new materials with the suitable adjustment of the mechanical properties and the lifetime according to the different application conditions. Even though a great effort is currently focused on the studies of the homogeneous PLA/PCL blends, there is less research on the PLA/PCL functionally gradient material (FGM). Combined with the conception of FGM and the principle of melt blending, a new processing method using conventional nonwoven facilities to prepare PLA/PCL FGM with double gradient functions in tenacity and biodegradability will be put forward. The flat or tubular PLA/PCL FGM will be prepared by the twin-screw-extrusion/ folding or winding/ thermal bonding process. The separate feeding of two components and reactive compatibilizer in a time-dependent fashion will generate the spatial gradation in the composition of the extrudates, which will be subsequently folded or wound around a mandrel and then thermal bonded. The mechanical properties of the FGMs depend directly on the weight ratio of the components, therefore the tenacity and biodegradability of the FGMs vary gradually along the flat FGM thickness and the tubular FGM radial direction. The control of the two component feeding rates and processing parameters will realize the flexibility and adjustable dimension of the PLA/PCL FGMs.Through the fibrillated cluster compressing molding and free extension methods, the self-reinforcing property will been imparted to the PLA/PCL FGMs. Structures and properties of these flat and tubular FGMs will be characterized by high-throughput and combinatorial method. The main factors on the properties of PLA/PCL FGMs will be analyzed. The database of the physical parameters of PLA/PCL FGMs, such as mechanical properties and degradability, will be established and be used to predict the properties of FGMs and design the tailor-made FGMs. The proposed fabrication method is simple, cheap and repeatable, which is suitable for the preparation of relatively large-scale FGMs of thermoplastic polymers using the conventional nonwoven processing facilities.The database will play an important theoretical guiding role for the design and development of FGMs and homogeneous materials.

目前关于性能互补的聚乳酸（PLA）和聚己内酯（PCL）共混改性的研究很多，但将PLA/PCL共混体系设计成梯度化结构却鲜有报道。本课题融合梯度材料的思想与聚合物共混改性原理，提出利用传统的非织造聚合物成网设备，借助组分调控法，采用独立进料、实时调控的加料方式和挤出-卷绕-热风粘合、挤出-铺叠-热压粘合的技术路线，制备兼具韧性和生物降解性双梯度功能的管状和板状PLA/PCL材料。通过组分分布的梯度化设计及加工工艺的控制，实现梯度材料刚柔相济和尺寸可调，借助纤维集束热压成型和定向自由拉伸赋予自增强性能。利用高通量组分方法揭示梯度材料性能与微观结构的关系，筛选影响材料性能的主要因素，建立PLA/PCL梯度材料的力学性能、生物降解性能等的物性数据库。本项目不仅获得一种简单、高效的大尺寸梯度材料制备新方法，而且建立的数据库对指导PLA/PCL梯度材料和均质材料的开发具有重要的理论价值和推动作用。

目前关于性能互补的聚乳酸（PLA）和聚己内酯（PCL）共混改性的研究很多，但将PLA/PCL共混体系设计成梯度化结构却鲜有报道。本课题融合梯度材料的思想与聚合物共混改性原理，借鉴干法铺网的设备，在传统的非织造聚合物成网设备上，将原有的接收帘网改造成双网夹持式铺网装置，熔融挤出的长丝纤网始终在双帘夹持下运动，不会受到意外张力和气流的干扰，既可提高铺网速度，也可保证长丝纤网的均匀性。铺网的速度和铺网宽度可调，可满足0~60cm宽的长丝纤网的往复铺叠，经热轧后用于制备大尺寸板状梯度功能材料。.根据所制聚合物梯度材料对组分和性能的要求，将原料组分按梯度比例进行级分配料。利用改造的纺粘设备对PLA和PCL及PEG熔融共混，借助组分调控法，采用两套加料系统独立进料、实时调控的加料方式以及熔融挤出－铺叠－热压粘合的方法，制备60cm大尺寸共混型板状PLA/PCL对称和非对称梯度材料以及PLA/PEG梯度材料。在材料厚度方向上，梯度材料具有良好的组分梯度分布以及梯度热稳定性能和生物降解性能。共混体系在厚度方向上呈现了不同的结晶度，但都表现出典型的热力学不相容体系。PLA/PCL和PLA/PEG共混可以使两者的力学性能在一定程度上互补，克服单一材料力学性能上的缺陷。.通过调节铺网机的铺网速度，制备阶梯密度的PLA吸音材料，与均质材料相比，阶梯密度吸音材料在厚度方向上密度发生变化，可以更好得发挥在各个音频的吸音效果。同样平方米克重的吸音材料，具有阶梯密度的材料具有更好的吸音性能，可更快的达到汽车内部舒适的温度及用更少的能量保持车内的温度。利用原子转移自由基聚合在PLA纤维表面接枝亲水性的PVP，可显著提高PLA的吸水性能，改善PLA梯度功能材料表面的强疏水性。.本项目不仅获得一种简单、高效的大尺寸梯度材料制备新方法，而且PLA/PCL梯度材料和均质材料的开发具有重要的理论价值和推动作用。