Effects of calcium stearate addition of ultrahigh molecular weight polyethylene in direct compression molding

Abstract

ABSTRACT:The effects of calcium stearate addition in molding of ultrahigh molecular weight polyethylene (UHMWPE) were investigated by tensile testing, scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectroscopy, and elemental analysis. Four types of UHMWPE specimens with varying contents of calcium stearate (Ͻ5, 50, 100, and 1000 ppm) were used in this study. SEM observation revealed that calcium stearate added specimens have smoother and more homogeneous microstructures. After accelerated aging, subsurface oxidative degeneration was observed in all specimens; however, calcium stearate added specimens had less oxidative degeneration in comparison with specimens without additives. Specimens showed better mechanical properties with increasing content of calcium stearate. Though all specimens aggravated their mechanical properties due to oxidation after accelerated aging, the specimens of 100 ppm of calcium stearate showed better properties at 3.7 MPa larger yield strength and four times larger value of elongation at fracture than the specimens without additives. These results indicate that calcium stearate addition produces dense packing of UHM-WPE particles, which brings about stronger fusion among the particles and fewer structural defects, and results in better mechanical properties and better resistance to oxidative degeneration.

Effect of europium(II) stearate on the mechanical properties and the oxidation resistance of UHMWPE

“…This is consistent with the results reported for the UHMWPE with homogeneously mixed calcium stearate (Utsumi et al, 2003). The unexpected drop in ultimate displacement after the irradiation treatment may stem from an interaction of the additive with the processing, which suggests the need to optimize the polyethylene consolidation process.…”

Europium Stearate Additives Delay Oxidation of UHMWPE for Orthopaedic Applications: A Pilot Study

“…These concentrations were chosen based on literature data of calcium stearate and antioxidant addition to polyethylene [8,38,40,41,43,44]. All three groups underwent simultaneous gamma irradiation (35.1 kGy) and thin-film accelerated aging (95°C), the latter adopted from previous studies [8,15,20].…”

Effects of calcium stearate and metal hydroxide additions on the irradiated LDPE/EVA compound properties

“…Compounds with lower CS content showed lower TS values. Fillers such as CS, as a lubricant and a modifier to allow the interaction of free radicals with the irradiated polymer matrix, rendered high crosslink bonds for the polymer matrices [7]. Therefore, addition of CS improved the TS values.…”

“…Increasing irradiation extended the crosslinking density and deterred the elongation of the LDPE/EVA compounds at high temperatures [4]. The physical adhesion forces and formation of hydrogen bonds between MH and EVA were stronger than those between ATH and EVA [7]. Therefore, LDPE/EVA compounds containing MH can resist elongation at high temperatures more than LDPE/ EVA compounds containing ATH.…”