Principles of accelerated ageing

Polymers that are suitable to be implanted in the body should not deteriorate unacceptably during their shelf-life or while in vivo, in addition, neither they nor any packaging materials should deteriorate before implantation (Hukins et al., 2008). One method that can be used to study the material s ageing properties is from retrieval studies in the human body (Dole el et al., 1989a), where implants are retrieved, after many years inside the human body, and the properties of their constituent materials investigated, or to implant it 

1 A common approach used to express the rate of ageing of polymers 

A method that ean be used to determine whether deterioration is likely to occur over long timescales, is to subject materials to elevated temperatures, a process known as accelerated ageing (Hemmerich, 1998 Hukins et al., 2008 Mahomed et al., 2010a). This is particularly useful to study the ageing of materials that are regarded as potential implant material. 

A common approach is to assume that the rate of ageing is increased by a factor of (ASTM-WK4863, 2005 Hemmerich, 1998 Hukins et al., 2008)  

Hukins et al. (2008) show that, substituting/ = 2 and AT = 10 °C (the 10-degree rule), into equation [8.4], gives an activation energy of 107 /loge2, which if substituted into equation [8.3] yields a value for/that is identical to the predictions of/with the empirical 10-degree rule. 

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