The effect of high-energy electron beam on drawnand undrawn high density polyethylene fbers

HDPE monoflaments were obtained using different extruders and drawn by post-extruder equipments. After solidifcation, drawn and undrawn monoflaments (draw ratio 7:1) were irradiated with 10 MeV electron beamsin air at room temperature at 25, 50, 75, 100 and 125 kGy doses to induce a network structure. The phenomenonof the HDPE crosslinking was studied on the basis of gel content measurements. The fbers were examined bydifferential scanning calorimetry (DSC) and mechanical properties measurements. It was noted that the gel fractionincreased with the irradiation dose up to 75 kGy and showed a signifcant increase with draw ratio, but at higherdoses remained without considerable change. Melting temperature of drawn fber increased with raising irradiationdose but decreased in undrawn sample. Also a bimodal endotherm peak was observed for drawn polyethyleneirradiated in air. The changes in melting temperature and appearance of bimodal endotherm were related to theradiation chemistry of polyethylene in the presence of oxygen and interlamellar interactions. Heat of fusion anddegree of crystallinity slightly increased for undrawn and drawn samples but, heat of crystallization was reducedby increasing irradiation dose due to the increase in the degree of crosslinking. The results of mechanical propertiesrevealed that no signifcant changes occurred in Young’s modulus by increasing irradiation dose. As a result ofoxidative degradation happened by the presence of the oxygen molecules during the irradiation process, the tensileproperties of irradiated fbers decreased but elongation-at-yield for undrawn and elongation-at-break for drawnfbers boosted by increasing irradiation dose up to 125 kGy. Polyolefns J (2015) 2: 109-119

Keywords:

polyethylene fber , electron beam , crosslinking , draw ratio