Effects of Zinc Borate, Aluminum Hydroxide, and Magnesium Hydroxide on Flame retardancy and Mechanical Properties of Fiberglass Reinforced Epoxy Composite Materials

Research Background and Experimental Design Fiber reinforced polymer composites are widely used in fields such as automotive, aerospace, and defense due to their excellent performance. In the automotive field, such materials have high requirements for flame retardancy, but the flame retardancy of traditional fiber-reinforced composite materials is often insufficient to meet higher fire safety requirements. Therefore, a study published in Fire and Materials systematically investigated the individual and synergistic effects of zinc borate (Z), aluminum hydroxide (A), and magnesium hydroxide (M) microparticles on the flame retardancy and mechanical properties of glass fiber reinforced epoxy composites. In addition to the single additive system, a multi-component mixture formulation containing Z, A, and M particles was developed to compare the efficacy of single component and multi-component systems. In the preparation process of composite materials, flame retardant additives are added to the epoxy matrix in different weight percentages and combinations, and then laminated using hand lay up molding method. Afterwards, the composite material samples were subjected to horizontal combustion testing, as well as bending and impact mechanics testing in accordance with international standards.

Mechanical properties and flame retardant test results

Mechanical tests show that unfilled (pure) composite materials have the highest bending strength and impact strength.

. As the content of additives increases, the agglomeration of particles caused by high surface energy forms stress concentration points, resulting in a slight decrease in mechanical properties. The flame retardant test showed the opposite trend: micron particle reinforcement significantly reduced the horizontal combustion rate. Specifically, the samples containing 20wt.% flame retardant additives (20A, 20Z, 20M, 10A10Z, and Hybrid2) showed a 41.97%, 47.68%, 12.95%, 35.02%, and 23.20% decrease in combustion rate compared to pure composite materials, respectively. Overall, the fire suppression efficiency of a single zinc borate formula (20Z) is superior to that of a mixed combination, providing a practical optimization path for fire safety automotive composite material structures.

Inspiration for the Polymer Additive Industry

Although this study focuses on epoxy composite materials, its data on the synergistic effects of zinc borate, aluminum hydroxide, and magnesium hydroxide have reference value for the design of flame retardant materials in the fields of construction and home decoration.

. In building materials such as PVC profiles, sealants, and architectural coatings, the interface compatibility between flame retardant fillers and matrix resins also affects the mechanical balance of the final product. Research suggests that a single zinc borate system may reduce the total amount of additives used to achieve similar flame retardant goals, thereby alleviating mechanical losses caused by particle aggregation. In addition, the horizontal combustion testing method used in this study and the mechanical evaluation conducted according to international standards provide a reference experimental framework for the screening of flame retardant formulations for building materials. For outdoor building materials that require a balance between weather stability and flame retardancy, the formulation design also needs to consider the interaction between antioxidants, light stabilizers, and flame retardant fillers to avoid performance degradation during long-term aging. Although the study did not involve weathering aging testing, its findings on particle agglomeration and stress concentration remind us to pay attention to the impact of filler dispersion process on the effectiveness of weathering stability system in PVC profiles and other products. The research conclusion is based on specific epoxy composite material systems and testing conditions, and caution should be exercised when extrapolating to other polymer matrices and building materials applications.

Information source:Effects of Zinc Borate, Aluminum Hydroxide, and Magnesium Hydroxide on the Flame‐Retardant Performance and Mechanical Properties of Glass Fiber‐Reinforced Epoxy Composites， Organized by Herun Chemical.