Cross-linked polymer content in polyamide

A simple and reliable procedure for the determination of cross-linked content in polyamides is introduced. The cross-linking, triggered e.g. chemically, by β-electron or γ-radiation, of thermoplastic materials such as polyethylene (PE), polyamides (PA) or certain thermoplastic elastomers (TPE) usually leads to an increase in the performance of these materials, e.g. creep resistance, heat resistance, wear behavior. The determination of the cross-linked content of polyethylene PE-X is an industrially frequently used method and is carried out according to ISO 10147. In this method, the soluble thermoplastic components are extracted from a small sample quantity (approx. 0.2 g) using boiling xylene as a solvent for 8 hours extraction time. The insoluble material is then determined gravimetrically. Methodically, the determination of the cross-linked content in polyamides PA6-X or PA66-X is not standardized. In publications or from suppliers of commercial raw materials, methods are based on the procedure described above, including the extraction with cold or boiling formic acid, cold or hot sulfuric acid, hexafluoroisopropanol or m-cresol. Most listed solvents are either highly toxic or corrosive. Therefore, in this application note, several polyamide 66 (PA66) samples are extracted with formic acid on the UniversalExtractor E-800 using the Hot extraction method. The cross-linked content is determined gravimetrically.

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