Polyethylene microtomy

Ultra-high molecular weight polyethylene (UHMWPE) has been used in orthopaedic prosthetic surgery for many years due to its excellent mechanical properties and frictional resistance. A large number of studies on both retrieved prostheses and raw material have, however, been necessary in order to understand and prevent degradation of the prostheses. The shape of the prostheses and the compression moulded blocks from which they are cut is usually not suitable for examination. In a number of studies microtomy has therefore been used in order to produce pieces suitable for further studies [112, 113, 114, 115, 116, 117, 118, 119, 120]. However, very often when microtomy is used, it is without any consideration of the fact that the process... 

This method has been applied to experiments of multiple internal reflection infrared spectroscopy on thin films of commercial polyethylene [120]. It is known that optical microtomy can be achieved by changing the incidence angle of the incoming beam. Structural depth profiling has then be performed thus allowing to probe the ordered-disordered structure of such films (Figure 3-32). 

Microtomy is commonly used to expose the interior of samples. Diamond knives or freshly cleaved glass knives are required for the preparation of suitably smooth, undeformed faces. One of the problems associated with sample microtomy of polyethylene is the potential for destroying the features of interest by smearing the relatively soft surface. This problem is especially prevalent in samples with low crystallinity. To reduce surface deformation to a manageable degree it is necessary to cut samples at temperatures well below their glass transition temperature, i.e., below -120°C. 

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