THE EFFECTS OF SUNLIGHT IRRADIATION ON THE MECHANICAL PROPERTIES AND STRUCTURE OF UHMWPE FIBERS

摘要

UHMWPE fiber is a kind of high performance fiber with ultra high modulus and high tenacity made from ultra high molecular weight polyethylene by the gel spinning and ultra hot-drawing process, which have found extensive applications in ropes, fishing nets, cordage, protective clothing and reinforcement of composites. Owing to its superior mechanical properties, UHMWPE filaments have been widely used in rigid structural, damage tolerant and impact resistant composites in aerospace, automotive, sports and other industrial or military industries. UHMWPE should in theory be sunlight stable on the basis of the fact that pure UHMWPE absorbs no radiation of wavelengths longer than 190nm. But internal and/or external impurities containing UV/light absorbing chromophoric groups such as hydroperoxides, carbonyls and unsaturated bonds are formed during polymerization processes and further processing and storage, which can change the absorbing wavelength up to 270-330nm and initialize the primary oxidative reactions. Although UHMWPE fiber has low amorphous fraction, owing to its high specific ratio of surface to volume, the deterioration of tensile properties and structure of UHMWPE fibers on the sunlight irradiation cannot be overlooked and should be taken into account before products designing and during products maintenance, and considering UHMWPE's 'good' light resistance, there are little reports on the effects of UV irradiation on the tensile properties and structure of UHMWPE fibers. The objectives of the present work were to investigate the tensile property and structure changes of UHMWPE filaments on sunlight simulating UV irradiation, and their implications on the complex morphologies of UHMWPE fibers.