Flame-Retardant Glass Fiber-Reinforced Epoxy Resins with Phosphorus-Containing Bio-Based Benzoxazines and Graphene

Area of Science:

• Materials Science
• Polymer Chemistry
• Fire Safety Engineering

Background:

• Glass fiber-reinforced epoxy resin (GFRER) is widely used but faces challenges with flammability.
• Developing effective flame-retardant materials is crucial for safety and performance.
• Novel additives like benzoxazine monomers and graphene offer potential solutions.

Purpose of the Study:

• To investigate the impact of cardanol-based phosphorus-containing benzoxazine monomer (CBz) and graphene on the flammability and thermal decomposition of GFRER.
• To evaluate the combined effects of CBz and graphene on material properties.
• To understand the mechanisms of flame retardancy and thermal degradation.

Main Methods:

• Preparation of GFRER composites with varying CBz and graphene content (up to 20 wt.%).
• Flammability testing including Limiting Oxygen Index (LOI) and UL-94 HB tests.
• Tensile mechanical property testing.
• Differential mass-spectrometric thermal analysis (DMSTA) to analyze thermal decomposition products.

Main Results:

• Addition of CBz, alone or with graphene, increased LOI and achieved self-extinguishing properties (UL-94 HB).
• Flame-retardant GFRER samples exhibited improved tensile mechanical properties.
• CBz promoted condensed-phase decomposition of high-molecular-weight products and reduced gas-phase release of low-molecular-weight products.
• Graphene addition increased relative intensities of high-molecular-mass peaks in thermal decomposition.

Conclusions:

• CBz and graphene are effective flame retardants for GFRER, enhancing both safety and mechanical performance.
• The additives modify the thermal decomposition pathway, contributing to reduced flammability.
• Combinations of CBz and graphene show synergistic effects in improving material properties.