JOURNAL OF POLYMER ENGINEERING

 Vol. 23, No. 2 2003, page 95

EXPERIMENTAL INVESTIGATION OF THE PROPERTIES OF HIGH-DENSITY POLYETHYLENE AFTER GAMMA IRRADIATION

João Carlos Miguez Suarez^1,*, Elisabeth Ermel da Costa Monteiro², Ronaldo Sérgio de Biasi¹ and Eloisa Biasotto Mano²

¹Departamento de Engenharia Mecânica e de Materiais, Instituto Militar de Engenharia, Praça General Tibúrcio 80, 2290-270 Rio de Janeiro, RJ, Brazil

²Instituto de Macromoléculas Professora Eloisa Mano, Universidade Federal do Rio de Janeiro, P.O. Box 68525, 21945-970 Rio de Janeiro, RJ, Brazil

 ABSTRACT

     Most studies of gamma irradiation effects on polyolefins are made using only two or three experimental methods. In the present work eight different techniques were used to study the properties of the same set of commercial high-density polyethylene (HDPE) samples after gamma irradiation. Rockwell hardness testing, determination of gel content, size exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), optical absorption in the infrared range (near IR), electron spin resonance spectroscopy (ESR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used to investigate the changes in the chemical, physical and mechanical properties of HDPE induced by gamma irradiation. The results confirm that for doses up to 100 kGy gamma irradiation of HDPE induces crosslinking. For higher doses, the ratio of crosslinking over chain scission decreases gradually with radiation dose and chain scission predominates. It was also observed that gel content, hardness, molecular weight and morphology are significantly affected by irradiation. These changes are interpreted in terms of structural changes in the polymer due to the production of free radicals and to a balance between crosslinking and chain scission.

 Keywords: high density polyethylene, gamma irradiation, degradation, yellowing

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