Resistance of Individual Polymers to Biological Media

PE-LD used for pipe lines or cable insulation is attacked by termites however, PE-HD is not attacked thanks to its toughness [32]. 

Polyethylene with a chloronaphthalene additive is very resistant to ants and termites, while polyethylene with 2% carbon black or 5% polyisobutylene is attacked [32]. 

In polyethylene, biological degradation is mostly found on additives caused by microorganisms and bacteria. In commercial polyethylene (in particular PE-HD), almost no biological degradation has been found. 

Degradation of starch weakens the polymer matrix. Degradation is also accelerated by the formation of peroxides that is caused by the addition of catalysts. This reduces molecular mass and in turn the degraded material is easier degradable by microorganisms. 

Polyethylene has been used in surgery since the 1950s. Experience shows that polyethylene cannot be used to replace soft tissue, but is a good substitute material for bone tissue (hip joint, pelvic bone). However, the first applications of PE-LD as bone tissue substitute resulted in high material wear. Subsequent developments in polymer synthesis led to a polyethylene with a higher molecular mass (PE-UHMW ultrahigh-molecular polyethylene (M, / = 4 10 g/mol)), that allowed wide application for pelvic prostheses. Table 5.129. 

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