Crosslinking and Sterilisation

As PE is a popular material for disposable medical devices, considerable effort has been applied to assess its response to radiation sterilisation. In experiments up to 75 and 200 kGy, it has been reported that most mechanical properties improve with radiation exposure. Slight discoloration due to phenolic-based antioxidants and particularly in combination with HAS was one detrimental aspect observed. Radiation resistance is measured by changes in properties. Bulk properties such as HDT and failure by yielding will be insensitive to surface degradation and will therefore imply high radiation resistance. Tensile properties are less sensitive to surface degradation than flexural ones. 

Sterilisation of disposable articles is generally carried out with a radiation dose of about 25 kj/kg or 25 kGy (2.5 Mrad). Due to the absence of tertiary carbon that initiates the degradation of the material and loss of mechanical properties, PE has a considerable radiation resistance. 

XPE is an important material for cable insulation in nuclear installations. In air, at 100 kGy of radiation at low dose rates, the strain at break (259%) of XPE is unaffected. Above a dose of 100 kGy, strain at break declines significantly and is sensitive to dose rate because of high oxygen permeability within XPE. 

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