Interfacial flame retardant unsaturated polyester composites with simultaneously improved fire safety and mechanical properties

Abstract The low flame retardant efficiency and poor interfacial property are the main problems that confine the wide application of glass-fiber reinforced unsaturated resin (GUPR) composites. Herein, these problems are effectively solved by grafting modified silane coupling agent on the surface of glass fiber and adding multi-element hybrid flame retardant to matrix. Firstly, phosphorus-containing flame retardant interface modifier (PKH550) and Sulfur-containing flame retardant (PCH3-S) were synthesized, and the structures were confirmed by Nuclear Magnetic Resonance spectroscopy (NMR) of 1H and 31P. Then PKH550 was successfully grafted on the surface of glass-fiber. Notably, compared with PGF/UPR 20% which had no rating in UL-94 test, the use of PKH550 modified glass-fiber made MGF/UPR 20% reached the V0 rating, and the limiting oxygen index (LOI) value was as high as 38%. In addition, with the increase addition of PCH3-S, the flame retardant properties of GUPR composites were gradually improved. Finally, the mechanical properties of GUPR composites had been improved further by the plasma method. Compared with the 296.93 MPa tensile strength of PGF/UPR, the tensile strength of P-PGF/UPR prepared after plasma treatment of glass-fiber increased to 319.27 MPa. This work provides a new angle to simultaneously improve the fire safety performance and mechanical properties of materials, which will not only be limited to the application of unsaturated resins, but can also have a rather good application prospects in other flame-retardant materials.