Final answer:
Increasing irradiation doses on ultra-high molecular weight polyethylene tend to improve physical properties like wear and tear resistance, chemical resistance, and fatigue resistance due to increased cross-linking within the polymer structure.
Step-by-step explanation:
When ultra-high molecular weight polyethylene (UHMWPE) is exposed to increasing irradiation doses, the material undergoes a number of physical and chemical changes. This type of polyethylene has extremely long chains, with a molecular weight numbering in the millions, which affords it a unique set of properties. The radiation can lead to the breaking of bonds within the polymer structure, using mechanisms such as cross-linking, chain scission, or a combination thereof, which in turn affects its overall properties.
Irradiation typically leads to an increase in cross-linking between the polymer chains, making the material denser and more crystalline. This can often result in enhanced mechanical properties such as improved wear and tear resistance, and better chemical resistance. Notably, there is also often an improvement in the material's fatigue resistance, which is an important factor in many of its applications, such as in medical implants and high-performance engineering parts.