There are different types of additives that can be added to this polyethylene to improve some of its properties, but regardless of the additive added, the main qualities that cannot be improved are abrasion and impact resistance.
This type of polyethylene is purchased in powder form which may contain pigments, ultraviolet absorbers, antistatic agents, crosslinking agents, flame retardants, fillers or compounds to create electrically or thermally conductive grades.
The additives should be added prior to powder processing and for this reason, the particle size should be similar to those of the plastic to facilitate dispersion.
Fillers and reinforcements such as wood flour, glass spheres, graphite and aluminum powder, talc, carbonates and silicates improve hardness and resistance to deformation under constant load, as well as aiding dimensional stability and modifying thermal expansion.
These additives can be present in concentrations between five and thirty percent. Crosslinking by means of 0.30 to 0.50% peroxide active ingredient improves wear resistance and reduces deformation under load by up to thirty percent. It is also feasible to apply the process for crosslinking with energetic gamma or beta rays, but the addition of antioxidants is required to avoid the degradation that causes the rupture of the molecular chains; however, this method can be applied after the molding of the articles.
Antistatic formulations contain between 5 and 6.5% conductive carbon black, exhibiting a surface resistivity of 10ˆ6 to 10ˆ9 ohms.
Protection against ultraviolet radiation is possible with absorbers such as carbon black at 2.5%. If the application requires another coloration to black, the formulation can contain 0.5% of other stabilizers, maintaining its qualities 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 conductivity to 2.5 W/m-K.
The flammability of Ultra High Molecular Mass Polyethylene is reduced by the addition of a mixture of halogenating compound and antimony trioxide.