# Green Fiber-Reinforced Laminates: Styrene-Free UPe with VTES-Functionalized ZrO2 and Flax Fabrics

## TL;DR

This paper explores using natural fibers and modified zirconia nanoparticles to create safer, stronger composite materials.

## Contribution

A styrene-free unsaturated polyester matrix with silane-functionalized zirconia nanoparticles is introduced for improved mechanical performance in natural fiber composites.

## Key findings

- ZrO2-VS nanoparticles improved dispersion and interfacial adhesion in the UPe matrix.
- Flax-fabric laminates with ZrO2-VS/UPe achieved a tensile strength of 72.2 ± 3.6 MPa.
- DMA showed increased storage modulus with minimal changes in glass transition temperature.

## Abstract

Natural fiber-based composites are gaining attention as sustainable alternatives to synthetic fiber-reinforced materials. Herein, styrene-free unsaturated polyester (UPe) nanocomposites and flax-fabric laminates reinforced with vinyl-triethoxy-silane (VTES) functionalized zirconia nanoparticles (ZrO2-VS) were studied. Nanoparticles were dispersed by high-shear mixing, and ZrO2-VS was benchmarked against unmodified ZrO2 and neat UPe. Fourier-transform infrared spectroscopy (FTIR) tracked cure conversion; scanning electron microscopy (SEM/EDS), tensile testing, and dynamic mechanical analysis (DMA) evaluated structure-property relationships. ZrO2-VS improved dispersion and interfacial adhesion, yielding higher tensile strength and storage modulus compared with unmodified ZrO2. In flax-fabric laminates, ZrO2-VS/UPe achieved a tensile strength of 72.2 ± 3.6 MPa, exceeding both unmodified ZrO2/UPe and neat UPe controls. DMA showed pronounced increases in storage modulus across temperature with small, non-significant changes in Tg. These results highlight a low-styrene-hazard UPe matrix and natural fiber reinforcement pathway to improved mechanical performance via silane-mediated nanoparticle-matrix-fiber bridging.