The flammability of polypropylene (PP) and recycled PP composite systems was thoroughly investigated by using cone calorimetry and thermogravimetry techniques in order to quantify the effect of brominated and chlorinated fire‐retardant systems. In this study, the efficiency of the fire‐retarding systems was defined from the relation between the amount of fire retardants and the characteristic quantities in cone calorimetry (M‐HRR, THR, and M‐EHC) and the limited oxygen index. The brominated fire retardants showed fire‐retarding capability superior to that of the chlorinated systems, and the recycled polymer was thermo‐oxidatively stabler than the pristine PP systems seemingly because of the fillers and blended polymers. Comparing the degradation behaviors of the composite systems in nitrogen and air environments, the halogen compounds retarded the decomposition rates in both cases, deactivating the reactive radicals of the polymer and restricting the flammable gases from being diffused into the unreacted polymer. Overall, the optimal amounts of fire retardants in different polymeric systems could be evaluated and correlated with several fire indicators in a relatively simple manner.
We introduce a simple growth model which exhibits a first-order pinning-depinning (PD) transition in disordered media. In our model, a first-order PD transition is triggered by the local inertia force F(l)=pLv macro where p denotes a constant between 0 and 1, L is the system size, and v macro is the average velocity in a local region of the growing interface. If p
p(c), our model shows a first-order PD transition. We measure the critical exponents characterizing the dynamical behavior of our model and explain how a first-order PD transition can occur if p>p(c). Besides the PD transitions, our model exhibits another phase transition from a fluctuating to a nonfluctuating interface with a constant velocity.
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