Total heat release reduction

Monomer Concentration Effect. In bulk polymerizations such as those conducted in the present study, the dependence of polymerization rate on monomer concentration can be determined only on the basis of the dependence of rate on the extent of reaction. Reduction of the rate vs. time DSC traces to digital data files permits computer calculation of reaction rate as a function of monomer conversion. A computer program which yields print-out of the rate and time at given fractions of the total heat release allows computation of the order of reaction with respect to carbon-carbon double bond concentration. Assuming -80.0 cal gm l represents the... 

Flammabihty studies using cone calorimetry at 50 kW m heat flux showed that incorporation of 5 wt% organoclay reduced peak heat release rate (PHRR) by 23-27% and total heat release (THR) values by 4—11%, depending on the clay modification. However, no simple correlation was observed between the FR efficiency and the degree of day exfoliation. The synergistic effect was observed for the combination of ammonium polyphosphate and 5 wt% amount of nanoday, which resulted in the total reduction of the PHRR of polyester resin in the range 60-70%. 

For instance, the effect of smoke reduction and flammability performance of zinc-based compounds (i.e. zinc borate and zinc hydroxystannate) in epoxy resin composites used in the aerospace and aeronautical industries have been analyzed (Formicola et al., 2011). The flammability performance of neat and loaded systems was analyzed by using micro-combustion calorimetry, while smoke generation, in terms of CO and CO2 production, was analyzed under dynamic conditions by using cone calorimetry. The experimental results have shown that the dispersion of zinc borate and zinc hydroxystannate within epoxy matrices leads to a significant variation in flame retardant properties in particular the total heat release is reduced by about 25% and 30%, respectively, and the heat release capacity by about 30% and 50%, respectively. The system containing zinc hydroxystannate shows an enhancement in all smoke reduction properties, and both compounds lead to a reduction of the CO2/CO ratio. 

The effect that silica gel/K2C03 has on the flammability of PS is shown in Table 5.5. The results are similar, but reduced in magnitude, to those for PP. Use of silica gel /K2CO3 additives causes the otherwise non-char-forming PS to produce a char yield of 6% (16% residue yield). The additives reduce the rate of heat release by 31%, reduce the total heat release by 11%, and similar to PP, had little effect on the CO yield and soot. The cone calorimeter results for PMMA are also shown in Table 5.5. PMMA is an inherently non-char-forming thermoplastic polymer however, using less than half the usual amount of additives, the reduction in flammability was comparable to PP and PS. Even at this low level... 

Very effective flame retardant data were obtained with styrene-butyl acrylate copolymer/graphite oxide (St-BA/GO) nanocomposites. "- The GO was prepared by oxidation of expandable graphite, and the St-BA/GO nanocomposites (GO content of up to 4% mass fraction) were synthesized by exfoliation- adsorption of monomer followed by in situ emulsion polymerization. The distribution of the GO particles was examined by XRD, TEM, and electron diffraction exfoliated GO layers in crystalline structures were observed. The thermo-gravimetric analysis (TGA) data show a slight increase in thermal stability (up to 15°C with a 3% mass fraction of GO). Significant reduction in heat release rate by increasing GO content has been reported all nanocomposites reduced about 40% of total heat released compared with that of St-BA, as shown in Figures 10.14 and 10.15. 

The mechanism of flammability reduction for polymer nanotube and nanofiber nanocomposites (Chapter 10) is similar to that for clays a nanofiUer-rich surface or barrier forms, which slows the rate of mass loss and therefore the rate of heat release. There is little reduction in the total heat release, indicating that the carbon nanoflbers and nanotubes only reduce the flammability of the... 

The heats of combustion of the volatile pyrolysis products released at various stages of volatilization were determined from untreated and chemically treated ponderosa pine (64). Fire-retardant treatments reduced the average heat of combustion for the volatile pyrolysis products released at the early stage of pyrolysis below the value associated with untreated wood at comparable stages of volatilization. At 40% volatilization, untreated wood had released 29% of its volatile products heat of combustion treated wood had only released 10-19% of its total heat. Of all the chemicals tested, only NaCl, which is known to be an ineffective fire retardant, did not reduce the heat content. This reduction in heat content of the volatiles was confirmed by using thermal evolution analysis (TEA) (55). 

Hapuarachchi [65] also measured the heat release rates (HRR) of PP and its different nanocomposites by cone calorimeter (Figure 12.24). The time to ignition was slightly anticipated probably due to an increased thermal conductivity induced by the presence of CNTs. Nevertheless, the peak of HRR experienced a reduction of 80%, from 1933 to 355kW/m2. The similar values of total smoke release (CO and CO2) suggested that the difference between... 

The principal effects observed in cone calorimeter tests are a marked reduction in peak and average rate of mass loss and in heat release. There appears to be little reduction in total heat of combustion or in smoke levels. The workers at NIST report that there seems to be little difference between intercalated and delaminated forms of nano-clay, despite evidence that polymer thermal stability can be more improved by the intercalated structure. 

The great improvements in flame retardancy caused by the organoclays also opened the possibility of decreasing the level of ATH within the EVA polymer matrix. The content of ATH needed to maintain 200 kW/m as a peak heat release rate could be decreased from 65 to 45 wt% by the presence of only 5 wt% organoclays within the EVA polymer matrix. Reduction in the total amount of these fillers resulted in improved mechanical and rheological properties of the EVA-based nanocomposite. 

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