Optimization of Mechanical Activation Modes for UHMWPE Dry Mixed Powders and Nanomodificators in the Planetary Ball Mill Pulverisette 7

Abstract

Introduction. Currently, in various technology areas, bronze, cast iron and other antifriction metals are replaced by polymer composites, which extend significantly service life of tribocoupling. An advanced antifriction polymer is ultra-high-molecular-weight polyethylene. The study deals with determining the optimal specific energy consumption for the mechanical activation of the polymer dry mixed powders and nanomodifiers in the planetary ball mill Pulverisette 7, which ensure the best complex of physico-mechanical and rheological properties of nanocomposites. Materials and Methods. In this work, we used GUR 4120 Ticona ultra-high-molecular-weight polyethylene with a molecular weight of 5 million, a Tuball Matrix Beta concentrate of activated carbon nanotubes at a concentration of 0.1%, calculated with reference to carbon nanotubes, and hydrophobic nanocrystalline silicon dioxide with a dispersion of 20 nm at the same concentration. Mechanical co-activation of polymer powders and nanomodifiers, when varying the specific energy consumption, was carried out in the planetary ball mill Pulverisette 7. The production of films from powders, for studying the elastic-strength and rheological characteristics of nanocomposites, was carried out with the use of the hydraulic press Gibitre. Tests were carried out respectively on the tensile testing machine UAI-7000 M and the rheometer Haake MARS III. Results. It has been established that the best physico-mechanical and rheological properties of nanocomposites are with specific energy consumption for mechanical activation of 3,000‒3,200 J/g that allows us to consider them optimal. The mechanical activation of ultra-high molecular weight polyethylene powder, reducing slightly the elasticity modulus and tensile strength of thermally pressed samples, does not affect the dynamic viscosity of melts at an energy consumption of 650‒4,550 J/g. Discussion and Conclusion. The use of carbon nanotubes and nanocrystalline silicon dioxide at a concentration of 0.1% can significantly improve the physical-mechanical and rheological properties of the polymer with energy costs of 3,000‒3,200 J/g for mechanical activation in planetary ball mills. Nanocrystalline silicon dioxide is a more effective modifier that can be explained by its better dispersion in the polymer matrix due to the lower tendency of nanoparticles to agglomerate.