Test MethodOptimization of the method of crosslinked portion determination in irradiated polyamide-6

Given the absence of a conventional determination method for polyamide-6 (PA-6) gels, the optimal conditions for gel content determination were investigated in crosslinked bulk PA-6 by dissolving the sample in 90% formic acid. The sample was wrapped in glass fabric and treated using three selected modes. Based on statistical testing of the results, a two-step procedure consisting of slowly stirring the sample immersed in solvent at room temperature in an orbital shaker for 48 h followed by solvent exchange after 24 h was chosen for extraction of the uncrosslinked, soluble portion. A correction was applied for the fraction of the glass fabric lubricant extractable by the solvent when calculating the crosslinked portion. Gel content of ∼70 wt.% was determined. The relative standard deviation was less than 5%.