Evaluation and Characterization of the Optical Properties of NBR Rubber/N220 Granular Carbon Black Composites

Abstract

This study investigates the optical and dielectric properties of nitrile butadiene rubber (NBR) reinforced with varying concentrations of N220 carbon black (CB). Ultraviolet (UV)–visible spectroscopy, in the range of 200–800 nm, was used. The optical spectrum showed a high absorption peak at approximately 220 nm, indicating that the material is suitable as a strong absorber of ultraviolet radiation. The direct optical band gap decreases slightly from 5.55 eV to 5.34 eV as CB content increases. The Urbach energy values, around 1.5 eV, suggest the formation of structural disorder and band tail states induced by CB–rubber interfacial interactions. The optical parameters such as extinction coefficient and refractive index exhibit characteristic variations around 220 nm, corresponding to strong absorption and high photon–carrier coupling. Dispersion behavior, interpreted through the Wemple–DiDomenico and Sellmeier models, reveals consistent variations in the effective oscillator energy, dispersion energy, and oscillator length strength. Dielectric analysis demonstrates that both the static and high-frequency dielectric constants are sensitive to CB loading, while the real part of the dielectric constant dominates over the imaginary component across the spectrum. Generally, the optical and dielectric findings demonstrate that the incorporation of N220 CB substantially modifies the energy band structure, optical dispersion, and charge carrier dynamics of NBR composites. These characteristics suggest their promising potential for optoelectronic and UV-sensing applications, where tunable optical absorption and dielectric response are critical.

Received: 24 August 2025 | Revised: 10 November 2025 | Accepted: 23 December 2025

Conflicts of Interest

The authors declare that they have no conflicts of interest to this work.

Data Availability Statement

Data are available from the corresponding author upon reasonable request.

Author Contribution Statement

K. Alfaramawi: Conceptualization, Formal analysis, Resources, Writing – review & editing. S. Abboudy: Formal analysis, Resources, Data curation, Writing – review & editing, Visualization, Supervision, Project administration. L. Abulnasr: Formal analysis, Investigation, Data curation, Writing – review & editing. S. Ebrahim: Investigation, Writing – review & editing. Ahlam K. Yousif: Methodology, Data curation, Writing – original draft.