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

Abstract

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.

Influence of Pore Structure and Metal‐Node Geometry on the Polymerization of Ethylene over Cr‐Based Metal–Organic Frameworks

“…[62] From an industrial point of view," good" is considered spherical with narrow particle size distributions,w hich is directly related to high bulk density,c ontrolled porosity,c ontrolled internal compositionand high process flowability. [63,64] Figure 3s hows the obtainedP Em aterials obtained from the ethylene polymerization reactions with the MOFs, and clearly demonstrates that one can affect the final PE morphologyb y selectingt he proper MOF polymerization template, at least under the here described reaction conditions.…”

“…Naturally, the PE morphology is highly important for assessing post‐reaction processability as well as preventing reactor fouling, often related to expensive reactor downtimes [62] . From an industrial point of view, “good” is considered spherical with narrow particle size distributions, which is directly related to high bulk density, controlled porosity, controlled internal composition and high process flowability [63, 64] …”

Tribological behavior of UHMWPE in water lubrication: the effect of molding temperature

“…This is because the bond between the UHMWPE particles was not strong enough to resist the interaction of tensile and shear forces, resulting in the formation of chipping pits and scratches on the severely deformed UHMWPE surface, followed by abrasive particles. Besides, abrasive particles would be involved in the UHMWPE surface due to the lubricant, exacerbating the abrasive wear (Zhang et al , 2020a, 2020b). As shown in Figure 7, if the abrasive particles were large and irregular, there are large fluctuations in the coefficient of friction.…”

“…Particularly, UHMWPE nascent powders were densified at 60°C under 120 MPa for 10 min, and they were melted at different temperatures (140°C, 160°C, 180°C, 200°C or 220°C) under 20 MPa for 30 min. Finally, when the powders were melted, the pressure was kept to 20 MPa, and temperature control was canceled for crystallization (Zhang et al , 2020a, 2020b; Deplancke et al , 2013). The manufacturing workflow is shown in Figure 2.…”

Bioactive Composite Nonwoven Surgical Dressing based on Cellulose Coated with Nanofiber Membrane using the layer-by-layer technique

“…While that the lowest color response K/S (1.34) was found with cotton material, this is related to mainly the density and weight of the available cotton nonwoven fabric. The increase in color properties can be explained generally because of the destruction of crystalline regions during swelling that leads to changes in microstructure and morphology of nonwoven samples [49,50].…”