Synthesis and performance of new modified reactive flame-retardant alkyd resin based on tetrabromophthalic anhydride as varnish for surface coatings

Abstract

There exist two distinct approaches to achieving flame retardancy in polymers, namely the additive type and the reactive type. In this case, new modified reactive flame-retardant (FR) alkyd resins (short, medium, and long oil alkyd) were produced by means of a condensation polymerization reaction between a linseed oil fatty acid and glycerol, to produce the monoglyceride as the ingredient source of the polyol used. This then reacted with phthalic anhydride, which was partially replaced with tetrabromophthalic anhydride (TBPA), as the ingredient source of the dibasic acid. The resulting resin was characterized using FTIR and 1H NMR spectral studies. The coatings of 50 ± 5 µm thickness were applied to the surface of wood, glass panels, and mild steel strips by means of a brush. The fire retardant capacity of the modified reactive FR alkyd resins was assessed using the limiting oxygen index (LOI) test. The physical, mechanical, and chemical properties were also examined to evaluate any drawbacks associated with the modification. The results of the LOI test indicate that the modified reactive FR alkyd resins exhibit an improved flame retardancy effect following an increase in the TBPA content within the alkyd resin backbone structure. Improvement to the mechanical properties of the modified resins was also observed, but chemical resistance was not significantly changed. Finally, the prepared reactive FR alkyd resins were observed to overcome a range of problems that weaken the attraction of additive FRs namely, poor compatibility, leaching, and the reduction in mechanical properties.