Characterization Of The Textile Fibers And The Blend Ratio By Pyrolysis-gas Chromatography/mass Spectrometer

Qualitative and quantitative analysis of textile fibers and their blends is important for the quality control of textile industry,textile markets and criminal investigation.In this paper,the characterization of textile fibers such as terylene,nylon,polyacrylonitrile and cotton,as well as analysis of the blend ratios of cotton with terylene were developed by the pyrolysis gas chromatography/mass spectrometry(Py-GC/MS).The decomposition mechanism of pyrolysis process for these textile fibers was also examined by Py-GC/MS.At first,the effect on the pyrolysis temperature and the chromatographic conditions were studied to optimize the experimental conditions.On the optimal conditions,the pyrogram of the textile fibers such as terylene,nylon,polyacrylonitrile and cotton are obtained.The results show that the pyrolysis products of different fiber has its own characteristic peaks,such as cotton containing levoglucosan,terylene containing benzoic acid,polyacrylonitrile containing 1,4-dicyano-2-butene and nylon containing caprolactam.Thus,the fibers can be distinguished from each other on the basis of these special pyrolysis products.Second,in order to investigate the repeatability of the pyrogram for the cotton fiber,five different origin and different forms of cotton fibers were analyzed by Py-GC/MS.The fact is that although the number of the peaks of pyrolysate obtained by samples with different form fiber was almost the same,their relative percentage of peak areas was quite different.The thermal decomposition mechanism for the textile fibers was examined by Py-GC/MS combined with thermogravimetric analysis.The results showed that the different of the relative percentage of peak areas was aroused via two thermal decomposition pathways.As we know that the structure of cellulose polymers basically consists of crystalline cellulose I,crystalline cellulose II and amorphous cellulose.The fact showed that different crystalline of cellulose may result in different thermal decomposition pathway.It is can be concluded that different forms of cotton fibers may have different crystalline.The thermal decomposition mechanism for three kind of synthetic fibers such as terylene,nylon,polyacrylonitrile were also be discussed.Lastly,a new solid sample preparation method for the determination of the blend ratio of cotton with terylene was developed.The sample was milled into powder with silica sands,and then a weighed 0.05 mg powder was introduced into the pyrolysis-gas chromatograph.Quantitative analysis is based on the peak area of the ethylene glycol dibenzoate,which is a characteristic pyrolysate of terylene.The calibration curves were linear(R2>0.998)over the range of 0.04-0.20 mg for terylene.The repeatability of the method was estimated from three consecutive injections of a standard cotton/terylene blend(80/20),with a relative sandard deviation(RSD)of 0.88%(n=3).An unknown cotton/terylene blend was also determined by the developed method,and the result is satisfactory.This study demonstrates the potential of Py-GC/MS for qualitative and quantitative analysis of the composition of textile fibers,in particular for the determination of the composition of the blend ratio of cotton/terylene textile samples.