Thermal evolution analysis

TEA (1) Thermal evolution analysis (2) Thermoelectric analysis (3) Thermal energy analyser... 

These studies fall into two groups,"dynamic" and"static heat treatments,In the dynamic heat treatment,samples are heated using a broad temperature range/20 to 300°C/ for a short time,Such tests include the Thermal Evolution Analysis/TEA/ and pyrolysis thin-layer chromatography /TAS/ /3,4/,... 

The normal degradation of cellulose to the flammable tar, levoglucosan, is reduced and the charring of this compound is promoted. Shafizadeh and coworkers used thermogravimetric (TG) and thermal evolution analysis (TEA) data, to confirm two different mechanisms involved in flameproofing cellulosic materials ... 

Figure 27. Block diagram of the thermal evolution analysis system coupled to a reaction coulometer detector.

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). 

THE CHEMISTRY OF SOLID WOOD Table VI. Effect of Inorganic Additives on Thermal Evolution Analysis ... 

Vo saturated vapor pressure of TEA thermal evolution analysis... 

Names rejected by the ICTA committee were effluent gas detection, effluent gas analysis, thermovaporimetric analysis, and thermohygrometric analysis. Also, terms such as mass spectrometric thermal analysis (MTA) and mass spectrometric differential thermal analysis (MDTA) should be avoided. Unfortunately, new names for the techniques are constantly being created, such as thermal evolution analysis (TEA). The technique of TEA, according to Chiu (18), includes all techniques that monitor continuously the amount of volatiles thermally evolved from the sample upon programmed heating. 

Hassel [103] has compared DSC, TG, thermal evolution analysis, TMA and DMA in evaluating flame retardant textiles based on different polyester fibres. Also the thermoanalytical analysis (DSC, TGA) of a sisal reinforced flame retardant poly-ester/(DBDPO, Sb203) formulation has been described [104]. Larcey et al. [105] have reported use of a simultaneous TG-DSC system (STA) to investigate the suitability of using magnesium hydroxide as a flame retardant and smoke suppressant in PP formulations. 

Fig. 2.42. Definition of thermal evolution analysis. After Chiu and Palermo [42]. Reproduced from Analytica Chim-ica Acta 81, J. Chiu and E.P. Palermo, 1-19 (1976), with permission from Elsevier.

Fig. 2.43. Thermal evolution analysis of antioxidant in polyethylene. After Gill [923]. Reproduced by permission of Du Pont.

Thermal evolution analysis is an excellent tool for polymer studies complementary to other thermal techniques such as DTA, TG and pyrolysis. Its applications include thermal degradation studies, determination of additives and contaminants, polymer composition and structure identifications. With small variations, the apparatus can also be used for vapour pressure measurements, and for determination of odorous materials in polymer systems. Coupling of TEA to GC for the identification of effluents is practicable and useful. TEA-CT-GC was used for the analysis of volatiles from ABS 10 ppb of styrene but negligible acrylonitrile was detected in the headspace of a typical ABS resin [42]. 

Low levels of antioxidants, such as 2,6-di-f-butyl-/ -cresol in /xg amounts of PE, have been determined by the first commercial thermal evolution analysis equipment based on the design by Eg-gertsen et al. [906] with flame ionisation detection (Fig. 2.43) [923]. The high sensitivity of FID can also be utilised for vapour pressure measurements... 

Fig. 2.44. Vapour pressure of di(2-ethylhexyl)phthalate by thermal evolution analysis. After Blaine [924]. Reproduced by permission of the author.

Chances for successful identification and quantification are considerably enhanced when analytes are separated. For solutions, chromatography is the supreme tool, whereas for solids some form of thermal treatment may achieve fractionation of matter according to volatility. Vapour evolution from polymers may be controlled and studied by various means, such as sublimation, thermal distillation, vacuum TG-MS, thermal evolution analysis (TEA) including TVA, headspace techniques or thermal desorption. It is obviously desirable that evaporation of the additives takes place below the decomposition temperature of the polymer. In principle, this can also be realised in thermal-programmed pyrolysis (dry distillation in vacuum). Desorption processes are controlled by diffusion. 

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