There are different types of additives that can be added to this polyethylene to improve some of its properties, but regardless of the additive used, its main qualities—abrasion resistance and impact resistance—cannot be improved.
This type of polyethylene is purchased in powder form, which may contain pigments, UV absorbers, antistatic agents, cross-linking agents, flame retardants, fillers, or compounds to create electrically or thermally conductive grades.
Additives must be added before the powder is processed; for this reason, their particle size should be similar to that of the plastic to facilitate their dispersion.
Fillers and reinforcing agents such as wood flour, glass beads, graphite and aluminum powder, talc, carbonates, and silicates improve hardness and resistance to deformation under constant load; they also contribute to dimensional stability and help control thermal expansion.
These additives may be present in concentrations ranging from five to thirty percent. Cross-linking using 0.30 to 0.50% of the active ingredient peroxide improves wear resistance by up to thirty percent and reduces deformation under load. It is also possible to use this process for cross-linking with gamma or beta rays; however, antioxidants must be added to prevent degradation that causes molecular chains to break. This method, however, can be applied after the items have been molded.
Antistatic formulations contain between 5 and 6.5% conductive carbon black, exhibiting a surface resistivity of 10⁶ to 10⁹ ohms.
Protection against ultraviolet radiation is possible using absorbers such as 2.5% carbon black. If the application requires a color other than black, the formulation may contain 0.5% of other stabilizers, while maintaining its properties for five years.
Metal powders such as copper, aluminum, and bronze increase the thermal conductivity of this plastic. Levels of 30% aluminum or 10% graphite increase the thermal conductivity to 2.5 W/m-K.
The flammability of ultra-high-molecular-weight polyethylene is reduced by adding a mixture of a halogenating agent and antimony trioxide.