Abstract
A novel reactive phosphorus and sulfur-containing monomer (bis(acryloxyethyldiphenylphosphate)sulfone, BADPS) was synthesized to enhance the comprehensive performance of unsaturated polyester resin (UPR), and corresponding flame-retardant unsaturated polyester resins (FR-UPRs) with various amounts of BADPS were prepared by radical bulk polymerization. The flame retardancy and thermal and mechanical properties of the UPR samples were investigated by limiting oxygen index (LOI) measurements, cone calorimetry, differential scanning calorimetry (DSC), a thermogravimetric analysis (TGA), and a tension test. The results showed that the introduction of BADPS remarkably enhanced the flame resistance and high-temperature stability, as well as the tensile performance of UPR. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and Raman spectroscopy studies revealed that BADPS can efficaciously promote the formation of UPR char residue with an improved microstructure and increased graphitization degree, which enhancedthe high-temperature stability and char yield of UPR. Additionally, a thermogravimetry-Fourier transform infrared (TG-FTIR) analysis corroborated that the evolution of combustible volatiles from UPR decomposition was substantially restrained by the incorporation of BADPS, which is beneficial for the suppression of fire hazards in UPR.
Highlights
As extensively utilized thermosetting materials, unsaturated polyester resins (UPRs) are distinguished by their remarkable mechanical properties, facile processability, excellent chemical resistance, and highly competitive cost
flame-retardant unsaturated polyester resins (FR-UPRs) exhibited a higher Tg, enhanced tensile strength, and better toughness as compared to those of the pure UPR. These improvements in UPR are attributed to the characteristic molecular structure of Bis (acryloxyethyl diphenyl phosphate) Sulfone (BADPS)
The thermogravimetric analysis (TGA) results suggested that the introduction of BADPS notably improved the high-temperature stability of UPR, demonstrating a higher char yield and much reduced maximum mass loss rate (MMLR)
Summary
As extensively utilized thermosetting materials, unsaturated polyester resins (UPRs) are distinguished by their remarkable mechanical properties, facile processability, excellent chemical resistance, and highly competitive cost. Polymers 2020, 12, 1441 matrix-additive interfacial relationship usually lead to dramatic reductions in the physical and mechanical properties of polymer materials [3,4,5] As a consequence, these trade-offs should be taken into adequate account in both academic research and industrial applications. It is worth noting that, in addition to the environmental friendliness, reactive phosphorus-containing flame retardants have demonstrated convincing flame resistance when bound to polymers, especially those with a high oxygen content, such as polyester and epoxy resin [8,9,10]. The phosphorus element was incorporated into sulfone-containing polymers for improved performance in terms of both flame resistance and thermal properties [6,18,19].these modified materials can be further used as flame-retardant additives [20,21]. The effects of BADPS on the char formation and thermal decomposition of UPR were discussed, shedding light on the flame-retardant mechanism of FR-UPR
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