Characterisation of oligomers and additives from polymeric materials

A multi-stage scheme was developed for the separation of vinyl chloride (VC) oligomers. A low molecular weight fraction was isolated from poly(vinyl chloride) by Soxhlet extraction. The presence of VC oligomers up to decamer was demonstrated by high-performance size exclusion chromatography (HPSEC). Removal of polar impurities was accomplished by preparative adsorption liquid chromatography of the low molecular weight fraction. Recycle HPSEC with repeated injections permitted the accumulation of fractions of VC pentamer oligomers which were resolved into their isomers by high-performance liquid chromatography (HPLC) offline. These results were duplicated utilising a coupled column system comprising of recycle HPSEC connected on-line to HPLC. This coupled technique was then applied to the hexamer and heptamer oligomers which were resolved into their constituent isomers. Multi-stage schemes were then developed for the extraction, characterisation and quantification of low molecular weight compounds from nitrile (NBR), ethylene-propylene-diene monomer (EPDM) and silicone elastomers. Low molecular weight fractions were isolated from these elastomers by Soxhlet extraction. HPLC and SEC analysis was performed on these extracts followed by gas chromatography-mass spectrometry (GC-MS). Extracts from these elastomers were shown to contain various phthalates, diamines, phenols, hydrocarbons and thiazoles. In addition, analysis of the low molecular weight extract from the silicone elastomer disclosed the presence of a number of cyclic and linear silicone oligomers.