# Development of Bio-Based Benzoxazine V-fa/PEG/Carbon Black Composites: Thermal and Mechanical Properties

## TL;DR

This study develops flexible, thermally stable composites using bio-based benzoxazine, PEG, and carbon black for engineering applications.

## Contribution

The novel composite formulation achieves enhanced mechanical and thermal properties through optimized PEG and carbon black content.

## Key findings

- Adding 20 phr carbon black increased melting temperature from 70 to 83 °C and thermal stability up to 416 °C.
- Flexural modulus improved from 117.18 MPa to 456 MPa with 10 phr carbon black.
- SEM images showed uniform morphology and good filler dispersion in the composites.

## Abstract

In this study, the blends of bio-based polybenzoxazine (V-fa type) and poly(ethylene glycol) (PEG) with PEG contents from 50 to 95 wt% and different molecular weights were developed to improve the flexibility of thermosetting polymers. Of these blends, PEG 8k at 80 wt%, which exhibited the best processability, was selected for further development via compositing with carbon black (CB) from 0 to 20 phr. Differential Scanning Calorimetry (DSC) analysis revealed that the melting temperature (Tm) increased from 70 to 83 °C and glass transition temperatures (Tg) increased from –53 to –48 °C at 20 phr. Thermogravimetric Analysis (TGA) demonstrated high thermal stability, with Tdmax (for all CB contents) presented at ca. 416 °C. Moreover, char yield was increased from 10% (without CB) to 28% (20 phr), reflecting improved decomposition resistance. Mechanical properties demonstrated that CB significantly reinforced the composites. The flexural modulus and flexural strength were increased from 117.18 MPa (without CB) to 456 MPa (10 phr) and from 2.42 MPa (without CB) to 3.94 MPa (2.5 phr), respectively. The SEM images confirmed uniform morphology and good filler dispersion. Conclusively, the composites of 8k PEG 80 wt% filled with 2.5 phr of CB provided an optimal balance of mechanical and thermal stability and engineering polymer applications.