COMPARATIVE ANALYSIS OF INFRARED ABSORPTION PEAKS IN UNTREATED AND SILANE-TREATED GLASS FIBERS USING FOURIER TRANSFORM INFRARED SPECTROSCOPY

Abstract

Silane coupling agents are widely used to modify glass fiber surfaces to enhance chemical compatibility, bonding performance, and interfacial stability in composite materials. Fourier Transform Infrared Spectroscopy (FTIR) is a sensitive analytical method for detecting molecular-level changes following surface treatments.

Objective: This study aims to compare the infrared absorption characteristics of untreated and silane-treated glass fibers, with emphasis on identifying functional groups introduced or altered by silanization.

Methods: Glass fibers were divided into two groups: untreated controls and samples treated with a γ-methacryloxypropyltrimethoxysilane (γ-MPS) solution. FTIR spectra were collected in the range of 4000–400 cm⁻¹ using attenuated total reflectance (ATR). Characteristic peaks corresponding to silanol (Si–OH), siloxane (Si–O–Si), carbonyl (C=O), and methacrylate-related vibrations were analyzed comparatively.

Results: Untreated fibers showed prominent absorption bands associated with Si–O–Si stretching (~1100 cm⁻¹), Si–OH bending (~950 cm⁻¹), and O–H stretching (~3400 cm⁻¹). Silane-treated fibers demonstrated additional peaks and intensity changes indicative of successful surface modification. Notably, the appearance of a carbonyl stretching band around ~1715–1730 cm⁻¹, CH₂ asymmetric and symmetric vibrations (2920 cm⁻¹ and 2850 cm⁻¹), and enhanced Si–O–Si network peaks confirmed covalent silane layer formation. A reduction in free silanol-associated absorption also suggested condensation and crosslinking after treatment.

Conclusion: FTIR analysis revealed clear spectral differences between untreated and silane-treated glass fibers, confirming chemical bonding and formation of an organosilane layer..