The effect of high-energy electron beam on drawn and undrawn high density polyethylene fibers

HDPE monofilaments were extruded with different extruders. After solidification drawn and undrawn monofilaments (draw ratio 7:1) irradiated with 10 MeV electron beams in air at room temperature at doses were of 25, 50, 75, 100 and 125 kGy. The crosslinking of HDPE was studied on the basis of gel content measurement. The fibers examined by differential scanning calorimetry (DSC) and mechanical properties. It has been shown that gel fraction increased with dose up to 75 kGy and showed a significant increase with draw ratio but in higher doses remained without considerable changes. Melting temperature of drawn fiber increased with increasing irradiation dose but decreased in undrawn sample. Also bimodal endotherm was observed for drawn polyethylene irradiated in air. The changes in melting temperature and the appearance of bimodal endotherm are related to the radiation chemistry of polyethylene in the presence of oxygen and interlamellar interactions. Heat of fusion and degree of crystallinity slightly increased for undrawn and drawn samples but, heat of crystallization was reduced by increasing of irradiation dose due to crosslinking. Tensile properties decreased because of oxidative degradation. Elongation at yield for undrawn and elongation at break for drawn samples increase with irradiation dose up to 125 kGy and no significant changes seen in Young modulus by increasing the irradiation dose. The decrease of tensile properties occurs due to oxidation caused by oxygen molecules present in the system during the irradiation and elongation at break and yield increase for all samples. Young modulus was not changed significantly by increasing the irradiation dose

Keywords:

polyethylene fiber , electron beam , crosslinking , draw ratio