Preparation and Characterization of Cardanol-Based Flame Retardant for Enhancing the Flame Retardancy of Epoxy Adhesives

Abstract

Epoxy resin has a versatile set of applications due to its excellent properties. However, its easily flammable property limits further applications. A bio-based flame retardant, cardanyl diphenylphosphate (CDPP), was successfully synthesized via condensation reaction between cardanol and diphenyl phosphoryl chloride. The chemical structure of CDPP was confirmed via 1H nuclear magnetic resonance and Fourier transform infrared spectroscopy. To overcome the flammable property of epoxy resin, different amounts of CDPP were incorporated into the epoxy resin. The thermal stability of epoxy resin with CDPP was reduced due to its phosphorus component, which had a relatively weak bond. Meanwhile, the measured char residue of epoxy resin with CDPP was increased compared to its calculated value, which indicated that CDPP promoted the formation of char residue. The limiting oxygen index of epoxy resin with CDPP was enhanced as the amount of CDPP increased from 22.1% for EP0 to 32.7% for EP10. The maximum value of the heat release rate per unit area and total heat release values of EP10 decreased by 23.23% and 12.02%, respectively, as compared to those of EP0. Additionally, single lap shear strength confirmed the improvement in the adhesion property of EP5. The lap shear strength increased to 7.19 MPa for EP5 compared to 6.27 MPa for EP0. This behavior might be due to the higher polarity of the phosphorus components. Based on the findings gathered in the present study, the incorporation of a bio-based flame retardant (CDPP) in epoxy resin has the potential for improving flame retardancy and adhesion property, which will be promising for the industrial area.

Enhanced Thermal and Mechanical Properties of Cardanol Epoxy/Clay-Based Nanocomposite through Girard’s Reagent

“…To address these concerns, natural biomass phenols have been selected as potential substitutes for BPA. Cardanol, an extract derived from cashew nutshell oil, has garnered attention as a green bio-based alternative for the synthesis of EPs [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Typically, epoxy resin undergoes a chemical reaction with a curing agent to form a robust and highly crosslinked network, resulting in impressive thermal and mechanical properties [ 22 , 23 ].…”

“…Typically, epoxy resin undergoes a chemical reaction with a curing agent to form a robust and highly crosslinked network, resulting in impressive thermal and mechanical properties [ 22 , 23 ]. Despite the promising applications of bio-based polymers, cardanol-based EPs exhibit certain limitations, such as inferior thermal and mechanical properties, which restrict their use in certain fields [ 12 , 13 , 14 , 15 , 16 , 24 ].…”

A Novel P/N/Si-Containing Vanillin-Based Compound for a Flame-Retardant, Tough Yet Strong Epoxy Thermoset

“…In recent years, people have paid more attention to carbon emissions and environmental pollution issues in the preparation of polymers [ 12 ]. Emerging as the times require, renewable bio-based materials such as vanillin [ 13 , 14 ], phytic acid [ 15 ], cardanol [ 16 ], and furfural [ 17 ] have gradually become a new choice for the design of flame retardants thanks to their multiple reaction sites and renewable advantages. Among these raw materials, vanillin has active phenolic hydroxyl and aldehyde groups, making it a favorite in industrial production and an ideal choice for building multifunctional bio-based flame retardants [ 13 ].…”