Determination of extractable matter in polymers

A simple and reliable procedure for the determination of the extractable matter content in polymers is introduced. The characterisation, identification and quantification of solvent-soluble additives in polymers are of great importance in quality control as well as for identifying migratory components which are in contact with foods or the environment. Additives in polymers include stabilisers, plasticizers, lubricants and flame retardants with up to 50 % mass content. In the presented Application Note, several polyamide 66 (PA66) samples are extracted with the UniversalExtractor E-800 using the Soxhlet warm method. The polymers were mixed with different additives for electron beam cross-linking which increases toughness and durability and can therefore be used for example in heavily stressed gear wheels. To monitor the process, the polymers were extracted in different stages: 

• Untreated
• With additives
• With additives and after electron beam cross-linking

Untreated polymers may contain oligomers and stabilizer which need to be taken into account. Then, before electron beam cross-linking, the additives are not chemically bound and can therefore be extracted again. The cross-linking efficiency is examined by extracting the polymer after the electron beam treatment. Typical cross-linking aids are triallyl isocyanurate-based (TAIC-based) additives for example Taicros® or Taicros M® from Evonik, which are usually dosed in the range of 2 – 5%. The extractable matter content is determined gravimetrically. The procedure complies with the official method of ISO 6427.

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