Two series of inorganic melamine salts containing a tungstate or molybdate were synthesized as a flame retardant and smoke suppressant for flexible PVC, and their flame retardancy and smoke suppression were studied by limiting oxygen index (LOI), smoke density rating (SDR) test, cone calorimeter, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). It can be found that the presence of melamine tungstate or melamine molybdate causes an obvious increase in LOI and a decrease in SDR. The cone calorimeter results reveal that melamine tungstate or melamine molybdate can clearly change the decomposition behavior of PVC and form a char layer on the surface of the composites, consequently resulting in efficient reduction of the flammability parameters, such as heat release rate, smoke production rate, total smoke production, and so on. The TGA and SEM results demonstrate that melamine tungstate can delay the degradation of PVC and improve the stability of the char residue. Moreover, melamine molybdate and the PVC matrix form a novel intumescent flame retardant and smoke suppression system, in which the PVC matrix acts as the carbonization agent and molybdate as the acid source (Lewis acid). Molybdate can catalyze the dehydrochlorination reaction and promote the cross-linking reaction of PVC effectively. Melamine (MA) and the released hydrogen chloride can act as the blowing agent, which enhance the intumescence of the char. POLYM. COMPOS., 00:000-000, 2016.
A laboratory study was carried to investigate the recycled asphalt performance of recycled asphalt mixture. The recycled asphalt mixture is from the Guaxing road in Gansu Province. By extraction tests and combustion method test on recycled asphalt mixture, the content of recovery asphalt, penetration, softening point and ductility were measured. The chemical composition testing and rheological testing were conducted on the recovery asphalt and new asphalt. Results indicate that the recovery asphalt contain the high proportion of asphaltenes and the low proportion of aromatics and resins. With temperature increasing, the decrease in the complex shear modulus (G*) of the recovery asphalt is much larger than that of the new asphalt,the increase in the phase angle of the recovery asphalt is much larger than that of the new asphalt, too. All these lead to the recovery asphalt harden, poor liquidity and plasticity.
The recycled asphalt mixture was analyzed by the microstructure, grading variability and agglomerate degree evaluation from the Guaxing road. The results showed that some aggregate was more in quantity and smaller in the variation for the 9.5mm to 0.6mm material of recycled aggregate; the fineness modulus ratio (FMR) was 0.89, so the agglomerate degree of recycled asphalt mixture is relatively small, which had a little effect on the strength of the cold recycled mixtures; the gradation and unconfined compressive strength test of cement stabilized wasted asphalt mixture were made at different blending ratios; the reasonable range of the cold recycled utilization was 20% to 40% for the recycled old materials in Guaxing road.
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