Ultraviolet/ozone continuous surface modification of pet fiber for reinforcing in epoxy resin

Abstract

In this study, a continuous UV/ozone surface modification process of polymeric fiber for the production of continuous-fiber-reinforced polymer based composite has been proposed. The gas phase photo-reactor, using the conventional low-pressure mercury lamps as UV sources, and the economically-made ozone generator were designed and constructed. Polyethylene terephthalate (PET) yarns and epoxy resin were chosen to be reinforcement and matrix in our composite system, respectively. Five combinations of UV light and gas species, i.e. UV/N2, UV/air, UV/02, UV/air + 03, and UV/03 + 02, for treating PET yarn were performed. The effects of exposure time, i.e. 2, 5, and 10 min, in the reactor of the fiber surface to each treatment were also studied by varying the pull speed of the pulling mechanism. The unidirectional tensile testing specimens were prepared by arrangement PET samples into specific designed casting mold. The treatments led no significant effects to the tensile properties, maximum load and elongation to break, of PET samples. The samples were analyzed by scanning electron microscope (SEM) to determine the surface morphology, and by energy dispersive x-ray analysis (EDX) to determine the surface composition. All treatments, there were no surface morphology changes observed. The EDX results showed that the effect of the treatment to surface composition depend on concentration of reactive species in the gas, i.e. ozone, molecular oxygen, atomic oxygen, and singlet oxygen. UV/02 + 03 treatment gave the highest value of oxygen uptake (6.6 %). Tensile test of resulted composites was investigated to determine the effectiveness of the treatment on the mechanical properties of the composite properties. The most effective condition of the treatment was 5 min UV/02 + 03, which improved 63 % of tensile strength, 175 % of elongation to break, and 325 % of toughness, in comparison to nontreated PET composite. However, 5 min UV/air + 03 was found to be most cost-effective condition because there was no need for supply oxygen at this condition. The 5 min UV/air + 03 treatment improved 52 % of tensile strength, 126 % of elongation to break, and 270% of toughness, compared to nontreated PET composite.