Particle morphology, structure and properties of nascent ultra-high molecular weight polyethylene

The effects of particle morphology on the structure and swelling/dissolution and rheological properties of nascent ultra-high molecular weight polyethylene (UHMWPE) in liquid paraffin (LP) were elaborately explored in this article. Nascent UHMWPE with different particle morphologies was prepared via pre-polymerization technique and direct polymerization. The melting temperature and crystallinity of UHMWPE resins with different particle morphologies were compared, and a schematic diagram was proposed to illustrate the mechanism of UHMWPE particle growth synthesized by pre-polymerization method and direct polymerization. The polymer globules in the nascent UHMWPE prepared by using pre-polymerization technique are densely packed and a positive correlation between the particle size and the viscosity-averaged molecular weight can be observed. The split phenomenon of particles and the fluctuation in the viscosity of UHMWPE/LP system prepared by direct polymerization can be observed at a low heating rate and there is no correlation between particle size and viscosity-averaged molecular weight.

Characterization and Corrosion-Resistance Performance of Hybrid Co/UHMWPE Composite Biocoatings

Novel hybrid Co/UHMWPE biocoatings were obtained by electrochemical deposition of cobalt from a cobalt sulfate plating bath with ultra high molecular weight polyethylene (UHMWPE - particle size of 10 μm) as dispersed particles in order to provide possible biomedical coatings applications. The surface morphology and topography, roughness and chemical composition were investigated, as a function of UHMWPE particles concentration in the plating bath by scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive X-ray analysis (EDX). Electrochemical corrosion resistance investigations were carried out in simulating body fluid solution (SBF), using electrochemical impedance spectroscopy (EIS) method at different exposure times. The results proved a good corrosion resistance of the obtained hybrid Co/UHMWPE coatings.

Surface Modified UHMWPE Particles by Direct Fluorination Blended with Polyurethane for Enhancing its Wear-Resistant Performance

In this study, Ultra-high molecular weight polyethylene (UHMWPE) particles were surface treated by F2/N2 and F2/O2/N2 two direct fluorination routes. A great number of polar groups are grafted on the surface of UHMWPE particles after direct fluorination confirmed by FT-IR and X-ray photoelectron spectroscopy (XPS) characterization. Two kinds of surface modified UHMWPE particles were blended with thermoplastic polyurethane (TPU) by dissolving in solvent. The scanning electron microscope (SEM) demonstrates that the interfacial interaction degree between the two polymer phases is correlated with the chemical composition of a fluorinated surface layer. The TPU composite with the UHMWPE particle treated by F2/O2/N2 route obtains excellent tribological performance enhancement with significant decrease in wear loss, ranging from 192.9 mm3 to 97.8 mm3, about 49.3% reduction compared with the virgin TPU.

Promoted Chain Diffusion of UHMWPE/HDPE Blend by High Temperature Treatment

Ultra high temperature treatment was used to promote the molecular chain diffusion of UHMWPE/HDPE blend. At the same time, melt blended sample and solution blended sample were also prepared for a comparison. The phase morphology of the samples observed by scanning electron microscope (SEM) showed that the difference between HDPE and UHMWPE became smaller after high temperature treatment. While the UHMWPE particle could not be observed in solution blending samples. The results of rheological test showed that the elastic modulus and complex viscosity of treated samples are higher than that of untreated samples but still below the viscosity of solution blending sample. The results deem, high temperature treatment indeed promoted the chain diffusion of UHMWPE/HDPE blend and a good fusion between HDPE and UHMWPE is obtained as a result