# Development of Sustainable Red Algae–Sisal Fiber Composite Films via Doctor Blading

## TL;DR

This study creates sustainable composite films using red algae and sisal fibers, showing improved strength and thermal stability for biodegradable plastic alternatives.

## Contribution

A novel doctor-blading method is used to produce red algae-sisal fiber composites with enhanced mechanical and thermal properties.

## Key findings

- Thermal stability peaked at 30 wt% sisal fiber loading before slightly decreasing at 45 wt%.
- Mechanical strength increased by 37% at 30 wt% sisal fiber compared to pure red algae films.
- Sulfur content decreased while carbon content increased with higher fiber incorporation.

## Abstract

This study investigated the properties of red algae (RA) biocomposite films reinforced with natural sisal fibers and plasticized with glycerol. The polymer was extracted from locally sourced red seaweed and combined sisal fibers at varying fiber loadings (0–45 wt%) using the doctor blading technique. Composite films were analyzed using a variety of methods to evaluate the chemical composition, thermal behavior and mechanical performance. Infrared spectroscopy confirmed the presence of kappa-carrageenan as the dominant polysaccharide in the RA matrix, whereas elemental analysis verified the dilution of sulfur content and enrichment of carbon with increasing fiber incorporation. Thermal stability increased with fiber loading, peaking at 30 wt% sisal fiber before decreasing slightly at 45 wt% due to poor fiber dispersion. Mechanical testing demonstrated an optimal balance between strength and flexibility at 30 wt% sisal fiber, with a 37% increase in strength compared to the pure RA film. Overall, the findings demonstrate that sisal fiber reinforcement enhances the structural integrity and stability of RA-based films, supporting their potential as biodegradable alternatives to petroleum-based plastics.