Surface Modification of High Performance Polyethylene Fiber by Photo-oxygenation and Its Effect on Mechanical Properties of FRP

Surface modification treatment, which makes various reinforcing fibers compatible with resin matrix, is a very important process contributing to the final properties of products made of fiber reinforced plastic (FRP) and other composites. There are many kinds of surface modification methods available for reinforcing fibers. As one of the dry methods, there is a new surface modification method named photo-oxygenation treatment, in which the surface of reinforcing fiber is modified by ultra-violet irradiation in a flow of an oxygen gas containing ozone at atmospheric pressure. So, the surface of high performance polyethylene fiber (EF), which is promising as one of the advanced composite materials (ACM), was treated by photo-oxygenation and the modified degree was studied in comparison with corona treatment as a general surface treatment. The influence of modified EF on mechanical properties of EFRP made with epoxy resin was also examined. The results are as follows: (1) Photo-oxygenation treatment is useful for surface modification of EF, because the improvements on wetting properties to water and on flexural properties are equal or better than those of corona treatment. (2) Carbonyl group is introduced into the surface by photo-oxygenation treatment, and thereby the wetting properties to water are improved. (3) Flexural properties of EFRP composed of modified EF are better than those of EFRP made of non-treated EF.