Organo‐Phosphorus Flame Retardants for Poly(vinyl chloride)/Wood Flour Composite

A series of organo‐phosphorus flame retardants (FRs) were studied in order to investigate their flame retarding performances for poly(vinyl chloride)/wood flour (PVC‐WF) composite. The FRs used include diammonium hydrogen phosphate (DAP), aluminum hydrogen phosphonate (AHP), and triphenyl phosphate (TPP). The effects of incorporating different FRs into PVC‐WF were determined by UL‐94, TGA, FTIR, and field emission scanning electron microscope (FE‐SEM). The results revealed significantly improved flame retardancy and thermal stability of PVC‐WF in the presence of FR. V‐0 ratings can be obtained at loading of FR as low as 1 wt% for DAP and 1.5 wt% for TPP but the same rating is recorded for the mixture containing 20 wt% AHP. AHP mainly acted in condensed phase whereas TPP and DAP generated phosphorus volatiles and/or fuel dilution compounds. TGA analysis was utilized to calculate the kinetic parameters of PVC‐WF and PCV‐WF/FR as well as to study the interaction between FR and PVC‐WF. FE‐SEM and FTIR were used to examine the morphologies and chemical components of the residual char. The results showed that PVC‐WF/FR produced phosphorus‐containing moieties during decomposition, which could act as dehydration agents to form char layer to protect the mixture from further degradation. The flexural and impact properties of composite increased with addition of FR at low loading and decreased with high loading of FR. By the incorporation of TPP in PVC‐WF, the glass transition is decreased; however, the storage modulus in the low‐temperature glass state is increased. This effect is attributed to antiplasticizing ability of TPP for PVC‐WF system. POLYM. COMPOS., 39:961–970, 2018. © 2016 Society of Plastics Engineers