Preparation of Polymers

Plastics and polymers are normally quite soft. Many different sectioning methods have been used. A sharp razor blade or scalpel, or even a pair of scissors, can be used. The precision saw produces excellent surfaces, while an abrasive cut-off saw yields a bit more damage and a rougher surface. Blades and wheels for sectioning polymers are available from the different manufacturers. Damage from sectioning is quite easy to remove.

Surface quality can be degraded by abrasion from the debris produced during grinding and polishing. Mounted specimens are much easier to prepare than nonmounted specimens. Castable resins are preferred as the heat from a mounting press may damage or alter the structure of the specimen. However, there may be a visibility problem if a transparent, clear polymeric specimen is mounted in a clear, transparent epoxy. In this case, color resin, with its deep red color, will produce excellent color contrast between specimen and mount in darkfield or polarized light. Always use practices that minimize the exotherm during polymerization.

Preparation of plastics and polymers for microstructural examination follows the same basic principles as for other materials. Rough grinding abrasives are unnecessary, even for the planar grinding step. Pressures should be lighter than used for most metals. Water is generally used as the coolant, although some plastics and polymers may react with water. In such cases, use a fluid that will not react with the particular plastic or polymer. Embedding can be a problem with plastics and polymers. ASTM E 2015 (Standard Guide for Preparation of Plastics and Polymeric Specimens for Microstructural Examination) describes additional procedures for preparing several types of plastics and polymers.

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