A quantitative differentiation method for acrylic fibers by infrared spectroscopy

• Published in: Forensic science international 2005-07, Vol.151 (2), p.125-131
• Main Authors: Causin, Valerio, Marega, Carla, Schiavone, Sergio, Marigo, Antonio
• Format: Article
• Language: English
• Subjects: Acrylic fibers; Acrylics; Analysis; Biological and medical sciences; Chemical industry; Copolymers; Crystallinity; Crystallization; Fibers; Forensic medicine; Forensic science; Forensic sciences; Infrared spectroscopy; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Polyacrylonitrile; Public health. Hygiene; Public health. Hygiene-occupational medicine; Spectrum analysis; Studies; Textile fibers; X-ray diffraction
• ISSN: 0379-0738; 1872-6283
• DOI: 10.1016/j.forsciint.2005.02.004

Absorbance peak areas of nitrile (2240 cm −1), carbonyl (1730 cm −1) and C H (1370 cm −1) groups were obtained for 48 colorless acrylic fibers by infrared (IR) microspectroscopy. The carbonyl signal, related to the comonomers most commonly used in acrylic fibers, was ratioed against the nitrile and C H bands, pertaining to the backbone of the polymer chains. The ratios A 1730/ A 2240 and A 1730/ A 1370, a relative measure of the comonomer content in the fiber, were used to differentiate the samples. A decrease in the crystallinity of fibers has been noted with increasing comonomer content. Relative standard deviation (R.S.D.) of the ratios were 1 and 3% for repetitive analyses on the same location and along the length of the same single fiber, respectively. When different fibers of the same sample were examined, results were reproducible within 6%. This simple method can greatly enhance the evidential value of colorless acrylic fibers, being able to discriminate them and thus helping the Court to better assess their significance.