Kevlar纤维电子束辐照接枝改性及其环氧树脂复合材料的力学性能研究

Due to its smooth and inert surface, the wettability of aramid fibers is poor and interfacial bonding strength between aramid fibers and polymer matrices is relatively weak. To enhance the interfacial bonding strength between fibers and matrices and effectively utilize the excellent mechanical properties of fiber in composite materials, the surface of aramid fibers should be modified. In this project, Kevlar fibers are selected as the base material and will be modified to improve its surface wettability via grafting of vinyl monomers such as acrylamide and acrylic acid onto surface by EB radiation-induced grafting polymerization. Through the study of reaction kinetic and optimization of experiment parameters, a continuous EB radiation-induced grafting technique for modifying surface of aramid fiber will be preliminarily established. Meanwhile, the modified fiber will be further used as a reinforcement to prepare Kevlar/epoxy resin composites. The mechanical properties will be thoroughly evaluated to establish a relationship between modification of fibers surface and mechanical properties of composites, aiming to accumulate knowledge for preparation of high performance aramid fibers/resin composites.

芳纶纤维因其光滑和惰性的表面导致其与树脂复合材料浸润性差，界面结合强度低，需要对芳纶纤维表面进行改性才能增强其与树脂之间的界面结合强度，进而充分发挥芳纶纤维的增强效果。本项目拟选用Kevlar纤维作为基材，利用电子束辐照技术在其表面接枝丙烯酰胺、丙烯酸等单体来增加纤维的表面浸润性，通过对接枝反应动力学的研究，不断优化实验参数，初步建立一个芳纶纤维连续电子束照接枝改性方法。同时，以改性Kevlar纤维作为增强体制备Kevlar/环氧树脂复合材料，通过对复合材料力学性能的研究，建立起浸润性变化及反应增容作用与复合材料力学性能之间的关系，为制备更高强度的芳纶/树脂复合材料积累经验。

芳纶纤维复合材料以其高比强度、高比模量等优异性能在国防航天及民用领域有着广泛的应用，但是由于表面光滑及惰性，使得芳纶与基体树脂之间的浸润性比较差，难以充分发挥芳纶的增强效果。本项目选择Kevlar纤维作为基材，利用电子束对Kevlar纤维辐射产生自由基，进而引发丙烯酸单体在其表面进行接枝聚合。采用ESR对自由基进行研究，结果发现自由基浓度随着辐照剂量的增加而增加，随着温度的增加而降低。本项目以去离子水作为反应溶剂，系统的研究了辐射剂量，单体浓度及阻聚剂浓度对接枝率的影响。从结果来看，丙烯酸的均聚反应对于接枝率的影响比较大：过高的辐照剂量，过高的单体浓度以及较低的阻聚剂浓度会使得丙烯酸单体更加容易均聚，导致接枝率降低。采用SEM和XPS对接枝后的Kevlar纤维表面形貌和化学结构进行表征。从SEM结果来看，接枝之后的Kevlar纤维表面相对于原始纤维和辐照后的纤维明显变得粗糙。而XPS的结果显示接枝之后，Kevlar纤维表面的C(O)OH基团的含量明显增加了，这说明丙烯酸单体被成功的接枝到Kevlar纤维表面上。采用电子束预辐射接枝的方法对Kevlar纤维进行改性，其接枝率比UV或等离子体接枝改性要低一些，但是接枝率已经足够改变Kevlar纤维的表面性能。因此，电子束预辐射接枝技术是一种十分有效的芳纶纤维表面改性技术，在复合材料的制备应用中有着十分重要的潜在价值。