A quantitative differentiation method for acrylic fibers by infrared spectroscopy

Area of Science:

• Forensic Science
• Polymer Chemistry
• Analytical Chemistry

Background:

• Acrylic fibers are common in forensic investigations.
• Differentiating similar fibers is crucial for evidence analysis.
• Existing methods may lack sufficient discriminatory power for acrylic fibers.

Purpose of the Study:

• To develop a simple and effective method for differentiating colorless acrylic fibers.
• To quantify comonomer content in acrylic fibers using infrared microspectroscopy.
• To assess the evidential value of infrared microspectroscopy for acrylic fiber analysis.

Main Methods:

• Infrared (IR) microspectroscopy was used to analyze 48 colorless acrylic fibers.
• Absorbance peak areas of nitrile, carbonyl, and CH groups were measured.
• Ratios of carbonyl to nitrile (A1730/A2240) and carbonyl to CH (A1730/A1370) bands were calculated to determine comonomer content.

Main Results:

• Comonomer content was successfully determined using the calculated absorbance ratios.
• A decrease in fiber crystallinity correlated with increased comonomer content.
• The method demonstrated high reproducibility with relative standard deviations of 1-3% for repetitive analyses and within 6% for different fibers.

Conclusions:

• The developed IR microspectroscopy method provides a reliable way to differentiate acrylic fibers.
• Quantifying comonomer content enhances the evidential value of acrylic fibers in forensic science.
• This technique offers a valuable tool for forensic laboratories to discriminate between similar fiber samples.