Mechanism of enhancement of intumescent fire retardancy by metal acetates in polypropylene
作者：Zhang Y, Li XN, Fang ZP, Hull TR, Kelarakis A, Stec AA
關(guān)鍵字：Fire; Intumescent flame retardant; Polypropylene; Metal acetate; Rheology; Mechanism
論文來源：期刊
具體來源：Polymer Degradation and Stability, 2017, 136: 139-145
發(fā)表時(shí)間：2017年
The effects of cobalt acetate (CoAc), manganese acetate (MnAc), nickel
acetate (NiAc) and zinc acetate (ZnAc) as fire retardant additive in
intumescent polypropylene (PP) formulations containing PP/ammonium
polyphosphate (APP)/pentaerythritol (PER) are reported. The limiting
oxygen index (LOI) and vertical burning (UL94) tests and cone
calorimetry were used to quantify the enhancement. Environmental chamber
rheometry, thermal gravimetric analysis and the morphology of the
residual char were used to investigate the mechanism of enhancement. The
incorporation of small quantities of metal acetates had a significant
influence on the fire behaviour. As an example, 0.7 wt% MnAc improved
the UL 94 rating of PP/APP + PER (mass ratio 100/25, with APP/PER = 3/1)
sample from V-2 to V-0, while 1 wt% MnAc reduced the peak heat release
rate and the total heat release by 18% and 12% in the cone calorimeter.
Rheological data, cone calorimetry, and photographs of the residual char
showed how the fire retardancy of the systems were affected by the melt
viscosity, which depended on the loading of metal acetate. During
thermal decomposition, the metal acetates promote the crosslinking of
the polymer and the fire retardant, reinforcing the protective
intumescent layer. While, the effect is most potent at the optimal metal
loadings. At higher MnAc loadings, the benefit of a stronger char is
overwhelmed by the adverse effect of crosslinking on the transition char
layer. Thus, this paper offers a new insight into the mechanism of the
intumescent fire retarded PP system.