Silicone rubber, thermal analysis

Jansen and co-workers [86] have evaluated temperature-controlled outgassing processes of plastics and rubbers using both off-line and on-line TD-GC-FTIR-MS. Decomposition of polyesterurethanes by means of TG-Tenax off-line sampling followed by TD-GC-FTIR-MS revealed C02, H20, tetrahydrofurane, cyclopentanone, dicarbonic acid, aliphatic diols and esters [86]. The same authors have also described the detection of polychlorinated biphenyls (PCB) in 2,4-dichlorobenzoylperoxide cured silicone rubbers after outgassing products of a rubber silicone part obtained after desorption for 10 minutes at 200 °C in the thermal desorption cold-trap and subsequent analysis by means of TD-GC-MS. Using a mass range of 290-294 Da the MS can be used as a selective detector for these substances. 

Songmin et al. reported the preparation of chitosan hydrochloric acid salt and the effect in improving the dispersion of carbon nanotubes in different solvents and silicone rubber. It was also found that treated carbon nanotubes could be dispersed in the silicone rubber homogeneously based on SEM and XRD analysis. The incorporation of carbon nanotubes enhanced the thermal stability of the silicone rubber. They also significantly improved the mechanical properties of the silicone rubber matrix. From the FTIR spectra, it was befieved that chitosan hydrochloric acid salt adsorbed on the surface of the carbon nanotube and then interacted with silicone rubber matrix, resulting in the enhancement of dispersion of carbon nanotubes, improving thermal and mechanical properties in the resulting nanocomposites [124]. 

The characteristics of silicone rubber vary with both the kind and amount of additives used and the mixing and vulcanization conditions. Various thermal properties of silicone rubber can be inspected by means of thermal analysis. 

Differential scanning calorimetric (DSC) analysis has been widely used in examining the effect of various fillers in SR on thermal transition such as glass transition (T, melting points (T ) and crystallization temperature (T ). According to Katihabwa et al. [179], T of pure silicone rubber (-71.87°C) increases in the presence of 1, 5,10, and 20 wt% of CNT loading to -68.67, -64.91, -63.21 and -63.57 C, respectively. This is due to the presence of dispersed CNT,... 

The effect of thermally conductive particles on the thermal properties of silicone rubber was studied. Different sized aluminum oxide was blended with addition cured silicone resin at various crosslink densities and filler loading levels. Thermal impedance of each sample was measured. Statistical analysis of the experimental data showed that hardness was not affected by filler type/size or filler amount however, the amount of crosslinker was statistically significant with respect to hardness. 

Gorman [971] has described thermal desorption of volatile additives from rubber. The quantitative analysis of 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) in natural rubber by means of TD-GC-MS has been reported [1018a]. Off-line TD-GC-MS at 180°C of a 75/25 SBR/BR vulcanisate showed t-butylamine, CS2 and benzothiazole, indicative of the vulcanisation accelerator Vulkacit NZ (TBBS) [1019]. Analysis of seals for hydrocarbons and silicon-containing components by means of direct thermal desorption outperforms previous methods based on cyclohexane extraction and headspace techniques [1020]. 

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