Study On Identification And Determination Of PA6,PA66 Fibers Based On Pyrolysis Chromatography

Polyamide fibers,trade name for the nylon,refer to a class of synthetic fibers containing amide groups on the backbone of a molecule.They are widely used in apparel fabrics,carpets,belts,parachutes and so on.Polyamide fibers content has a great impact on the performance of its textile products and the price,related to the interests of producers,sellers and consumers.At present,the detection of polyamide fiber content is mainly based on national standards GB/T 2910.7-2009 "Quantitative Chemical Analysis of Textiles Part 7: Polyamide fiber and some other fiber mixture(formic acid method)".The method is based on the traditional chemical dissolution method.The whole processes are cumbersome,time-consuming,and require a large amount of samples and reagents.In this paper,a method for the rapid identification and determination of PA6 and PA66 fibers in blended fiber was established by pyrolysis gas chromatography-mass spectrometry(Py-GC/MS).According to the pyrolysis of PA6 and PA66 fibers,a mechanism of PA6 and PA66 fibers was proposed.Formic acid was used to dissolve PA6 and PA66 fibers,and performed thermal desorption and pyrolysis,studied the effect of pyrolysis temperature,desorption temperature and column flow on the pyrolysis results.The reproducibility of PA6 or PA66 fiber content in blended fiber was established by Py-GC/MS.The recovery rate of PA6 or PA66 fiber in the blended fiber samples was analyzed.The results showed that: the mainly pyrolytic products of PA6 and PA66 fibers were respectively caprolactam and cyclopentanone.PA6 and PA66 fibers could be identified by these two characteristic products.the cleavage of PA6 and PA66 occurred mainly between the amide bond and the carbon-nitrogen bond.PA6 produced caprolactam at the amide bond rupture,and at the carbon-nitrogen bond site,random cleavage produced cyano-containing dimer and multimeric derivatives of acrylamide;PA66 produced cyclopentanone,amine compounds,olefins and cyano-containing dimers and trimmers at the amide bond and carbon-nitrogen single bond.The Py-GC/MS analysis of PA6 and PA66 formic acid solution showed that the pyrolysis temperature had a great effect on PA6 and PA66 solution,the desorption temperature and Column flow is less affected.The content of PA6 and PA66 in mixed fibers was determined by Py-GC/MS.The recoveries of PA6 fibers were 81.8%-97.2%,and the PA66 fibers were 81.6%-109.6%.The deviation between the measured values of Py-GC/MS method and the national standard method was 1.2%%-9.1%,which indicated that this method was suitable for quantitative determination of PA6 and PA66 fibers.