Polymer flammability characterization

Case Study 2. High Throughput Polymer Flammability Characterization Using... 

CASE STUDY 2. HIGH THROUGHPUT POLYMER FLAMMABILITY CHARACTERIZATION USING GRADIENT HEAT FLUX ENVIRONMENTS AND RAPID CONE CALORIMETRY ... 

Thermal analysis, in the form of TG, has been employed extensively in the area of polymer flammability to characterize polymer degradation. 

Gilman JW, Davis RD, Shields JR et al. (2004) Development of high-throughput methods for polymer flammability property characterization. International SAMPE Symposium and Exhibition 460-469... 

Xie, R.C. and Qu, B.J. 2001. Expandable graphite systems for halogen-free flame-retarding of polyolefins. I. Flammability characterization and synergistic effect. Journal of Applied Polymer Science 80(8) 1181—1189. 

E. M. Pearce, Y. P. Khanna, and R. Rancher, Thermal Analysis in Polymer Flammability in Thermal Characterization of Polymeric Materials, edited by E. Turi, Academic Press,... 

The above flame retardants, HMPN and TMP, along with another commercially available alkyl phosphate, triethyl phosphate (TEP), were systematically characterized by Xu et al. To quantify the flammability of the electrolytes so that the effectiveness of these flame retardants could be compared on a more reliable basis, these authors modified a standard test UL 94 HB, intended for solid polymer samples, and measured the self-extinguishing time (SET) instead of the universally used flame propagation rate. Compared with the UL 94 HB, this new quantity is more appropriate for the evaluation of the electrolytes of low flammability, since the electrolytes that are determined to be retarded or nonflammable by this method all showed zero flame propa-... 

Gilman JW, Bourbigot S, Shields JR et al. (2003) High throughput methods for polymer nanocomposites research extrusion, NMR characterization and flammability property screening. J Mat Sci 38 4451... 

This term varies significantly with the nature of the fuel. Liquid fuels are characterized by the presence of recirculation currents induced by buoyancy. These currents homogenize the temperature distributions, reducing in-depth conduction. Nevertheless, convective motion transfers heat to the interior of the pool leading to an additional term of in-depth convection. Convective heat transfer in polymer melts has a similar behavior and could potentially have an important effect on burning rates nevertheless, the impact of polymer melt rheology on the flammability of materials is still a matter of great controversy. 

S. Zhang, A.R. Horrocks, T.R. Hull, and B.K. Kandola, Flammability, degradation and structural characterization of fiber-forming polypropylene containing nanoclay-flame retardant combinations, Polym. Degrad. Stabil., 2006, 91 719-725. 

Another study demonstrating the importance of conducting multiflux flammability tests was conducted by Panagiotou and Quintiere [33], Quintiere used modeling of flame-spread to show that a polymer system can be accurately characterized only if the flammability is measured over a range of heat fluxes ignition time, flame spread, and HRR need to be measured at various fluxes. 

The leading mechanisms of flame retardance of polymers may be related to physical or chemical effects at any stage of the combustion. As a rule, the chemical influences (characterized by the rate constants of the respective reactions) are closely interrelated with the physical ones (characterized by heat- and mass-transfer parameters). Establishing the role of each factor and estimating its individual contribution to the overall effect is important for the development of ways of reducing the flammability of polymeric materials. 

The flammability of the three polyarylethers 7, 8, and 10 was measured using the UL-94 V test, and all three samples obtained a V-0 rating when mixed with 1 wt.%1 PTFE as an antidrip additive. It is important to note that the samples were tested without antidrip additive, and did not burn but dripped excessively, making characterization impossible. It was observed that while these polymers where subjected to prolonged exposure to the Bunsen burner flame, the fire never consumed them. The UL-94 sample results are shown in Table 3. 

The first application of a quartz crystal for use as a nonisothermal thermobalance was reported by Henderson ei al. (66). This was accomplished through the use of a minicomputer to characterize the temperature-frequency relationship for the crystal and to correct numerically the frequency-temperature-mass relationship to obtain the TG curve of the sample. One advantage of such a system is that very fast heating rates may be employed due to small sample size (t-40 jug typical) and high sensitivity. Thin films of sample exhibit rapid gas diffusion and thus permit thermal equilibrium to be maintained at heating rates of l00°C/min or greater. Applications of this thermobalance include the evaluation of thin films and coatings as well as various polymer studies of pyrolysis, flammability, and so on. 

R 131 J.W. Gilman, S. Bourbigot, J.R. Shields, M. Nyden, T. Kashiwagi, R.D. Davis, D,L. Vander Hart, W. Demory, C.A. Wilkie, A.B. Morgan, J. Harris and R.E. Lyon, High Throughput Methods for Polymer Nanocomposites Research Extrusion, NMR Characterization and Flammability Property Screening , p. 1459... 

The flammability of a flame-retarded polymer is usually characterized by the oxygen index. Flame-retardancy is defined as the increase in the oxygen index compared to that of the original polymer. 

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