CORRELATION OF MECHANICAL AND CHEMICAL CHANGES IN
GAMMA-IRRADIATED ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE
João Carlos Miguez Suarez (a),*, Amal Elzubair (a),
Claudia Maria Chagas Bonelli (a), Ronaldo Sergio de Biasi (a),
Eloisa Biasotto Mano(b)
(a) Instituto
Militar de Engenharia / Departamento de Engenharia Mecânica e de Materiais
22290-270 Rio de Janeiro, RJ, Brazil
(b) Instituto
de Macromoléculas Professora Eloisa Mano
Universidade Federal do Rio de Janeiro
21945-970 Rio de Janeiro, RJ, Brazil
ABSTRACT
Ultra-high
molecular weight polyethylene (UHMWPE) is used in the manufacture of several
products due to its excellent engineering properties – high tensile and impact
strength, low friction coefficient, resistance to chemical attack and
biocompatibility. It is well known that gamma irradiation introduces structural
changes that may be detrimental to the integrity and performance of the
polymer, limiting its useful life. Plates manufactured with commercial,
general-grade, UHMWPE were exposed to several doses of gamma radiation at room
temperature in air. The structural changes of the plates were investigated by
gel content determination, mechanical testing (hardness, tension and impact),
differential scanning calorimetry (DSC), Fourier transform infrared
spectroscopy (FTIR), wide angle X-ray diffraction (WAXD), electron spin
resonance (ESR) and scanning electron microscopy (SEM). Experimental results
show crosslinking and an increase in crystallinity. More significant changes
are observed in samples irradiated with higher doses: chain scission induced by
oxidation changes the molecular structure, degrades the mechanical properties
and changes the fracture mechanism from ductile to brittle.
Keywords: ultra-high molecular weight polyethylene (UHMWPE); gamma irradiation; aging; degradation; ductile-to-brittle transition