Efecto del entrecruzamiento molecular sobre las propiedades tribológicas de polietileno de alta densidad

E. MOLINARI; M. FAILLA; W. TUCKART; P. RAMIREZ IBERNON

Santa Fé

Congreso; Congreso Iberoamericano en Ciencia y Tecnología de Metalurgia y Materiales 2014 IBEROMAT.; 2014

SAM

The use of polymers in important parts of devices subjected to sliding or in contact with surfaces in relative motion, has spread widely in engineering applications. The information available about the tribological performance of polyethylene is limited and is not fully known the manner that the molecular and morphological characteristics affect the wear resistance of the material. In the present study we investigate the wear behavior of crosslinked high density polyethylene (HDPE) in contact with steel, with the aim of knowing the influence of the molecular characteristics on the friction behavior of the polymer. Materials with different molecular structures were generated by modifying a HDPE with various concentrations of organic peroxide. The characterization included the technique of solvent extraction to determine the gel content, swelling measurements to obtain the molecular weight between crosslinks, calorimetric measurements to know the heat of fusion and Vickers microhardness. The tribological properties were evaluated by performing block-on-ring wear tests under controlled ambient temperature. The wear rate and coefficient of friction were obtained. The materiales were tested at different ring rotation velocities, 345 or 35rpm, and normal loads of 10, 15 and 20N were applied, while the sliding distance was the same for all tests. The wear rate was estimated from the mass loss of the specimens during the test normalized by the sliding distance.  It was observed that the wear rate initially increases, compared to the unmodified polyethylene, with the peroxide concentration, and then decreases until it reaches a minimum of aroun 10 times lower the wear rate of the unmodified material. The analysis of the  worn contact surfaces using optical microscope and scanning electron microscope (SEM) allows to establish the dominating wear mechanisms.