Flammability and mechanical behavior of cotton fiber polymeric composite laminate with polyurethane and alumina trihydrate

Abstract

This work aims to evaluate the mechanical and flammability behavior of the green laminate polymeric composite of polyurethane (PU) derived from vegetable oils with reinforcement of cotton fiber (CF) unidirectional fabrics and added alumina trihydrate (ATH). Specimens of PU and PU doped with different ATH contents (10%, 20%, and 30%) were manufactured by casting process and the CF/PU composites and CFs/PU composites with ATH by the vacuum bag process, with three different stacking sequences (fibers oriented on 0°, ± 45°, and 90°). Vertical and horizontal tests of flammability were performed, and the CFs/PU composite showed a higher burning rate than the pure polymer, the difference was a 50% higher speed. However, the addition of ATH to the composite showed an enhancement of its flammability, the smallest burning rate was exhibited. The PU/CFs laminate (0°) exhibited a tensile stiffness and strength twice that presented by the pure PU. Through the SEM (scanning electron microscopy) investigation, when, ATH was added to the composite, there was a decrease in the fiber-matrix interface quality, presence of voids, and larger occurrences of pull out, which explains, besides a smaller volumetric fraction of reinforcement exhibited, decrease in tensile strength.