Phenolics Thermogravimetric analysis

Fig. 16 Typical thermogravimetric analysis of sodium phenolate, illustrating the temperature resolution associated with the separate liberation of water and free phenol.

The thermal stability of these materials was examined by thermogravimetric analysis (TGA) and IR spectroscopy. As anticipated from their structures, the thermal properties of these polymers are far superior to those found in a typical diazoketone/phenolic resin resist. TGA (in air) of the material depicted in Scheme II shows that the polymer does not change in weight up to a temperature of 300°C. 

The mechanical properties of the C3, C6, and Cl2 nanocomposites were all significantly better than those of the neat phenolic resin, even if a very small amount of the silicate was used. Among the nanocomposites prepared, the organically modified MMT-resol systems showed better mechanical properties than those of the unmodified MMT-resol system. This improvement was attributed to the formation of an end-tethered structure due to the reaction of the carboxylic acid of the organic modifier with the methylol group of the phenolic resin. Thermogravimetric analysis reported by Byun and coworkers showed that the nanocomposite systems had similar thermal stability to that of the neat polymer. 

Weight Losses during Thermal Oxidative Degradation Showing Dependence on Temperature for Modified and Unmodified Phenolic Resins. Determined by Thermogravimetric Analysis. 

The thermogravimetric analysis (TGA) of solidified phenol-formaldehyde resins has shown that the ratio of the initial components influences the thermal stability of the polymers produced the most thermally resistant polymers were obtained with a phenohformaldehyde ratio of 0.5. 

The mechanisms for the pyrolysis of PSF were the same as those for the pyrolysis of PES, involving the sulfone, ether, and isopropylidene groups to produce sulfur dioxide, phenol, and l-methyl-4-phenoxybenzene as the major products. From the experimental results, it can be concluded that the thermal stability of the groups was in the following order sulfone < ether < isopropylidene. The relative stability of the ether group dominated the temperature of the maximum weight-loss rate in the thermogravimetric analysis. The mechanisms are shown in Equation 6.15. 

Thermal decompositions have been studied most effectively by mass spectroscopic thermal analysis, thermogravimetric analysis, and electrical conductivity. Several analytical characterizations of phenolic resins have recently been reported, making use of a variety of properties, including expansion coefficients, " specific heat capacity, ultrasonic properties, dipole moments, and laser light scattering. Recently, high-temperature properties of reinforced phenolic components have been studied by Goetzel. ... 

Fig. 21. Thermogravimetric analysis of phenolic resole resin, showing weight losses due to cure (30-300°C) and decomposition (400-650°C). 10°C/min in air. From Ref. 85.

Thermogravimetric analysis in conjunction with DSC has been used to measure Tg in phenol bark resins [3]. DTA has been used to measure Tg in bis(trichlorophenolate) di(pyridine) nickel(II) and bis(tribromophenolate) di(pyridine) nickel(II) complexes [12], PS [13], and various other polymers [14]. 

Proton NMR, differential thermal analysis (DTA), thermogravimetric analysis (TGA), and capacitance versus cure time have also been reviewed in connection with analyses of phenolic resins [27]. 

DSC studies on all the cured samples indicate incomplete cure with substantial exotherms still evident. Samples of the benzophenone and biphenyl monomeric moieties were cured at 500 F for 16 hours and their DSC s showed no evidence of exotherm in the 250 C region. An exotherm at 350 C (Figure 1) was related to the thermal decomposition of the materials. Thermogravimetric-mass spectral analysis was performed in vacuum on the benzophenone system at the same heating rate as the DSC scan. The ion intensity as a function of temperature is shown in Figure 2 and indicates that thermal decomposition starts at approximately 350 C with the evolution of phenol, biphenol, and water. 

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