Novel Hybrid Organic-Inorganic Polymeric Coatings Containing Phosphonium or Acidic Groups for Improving Flame Retardancy of Wood

Flame-retardant polymeric coatings with high limiting oxygen index (LOI) were prepared by combining inorganic mineral huntite (H5) and polymeric additives synthesized in the present work into a polymeric formulation. In order to improve the dispersion of the Mg- (and Ca)-based H5 particles, additives containing phosphonium and acidic groups were employed to homogenize the inorganic fillers into the polymer matrix. Specific blend combinations of the commercial matrix Ecrovin (R) LV 340 eco with huntite and the additives poly(benzyltriphenylphosphonium-co-4-styrene sulfonic acid) P(SSH-co-SSBTPB60) and poly(hexadecyltributylphosphonium-co-4-styrene sulfonic acid) P(SSH-co-SSTBHDPB80), combining acidic and phosphonium groups, led to LOI values of 34.5% and 33.5%, respectively. The novel flame-retardant polymeric coatings inhibited the combustion of the coated wood substrates, which is attributed to the combination of acidic groups that promote the dispersion of inorganic filler in the polymer matrix and phosphonium groups that support the increase in LOI values.