Dynamic load thermomechanical analysis

DSC helps in determining the glass-transition temperature, vulcanization, and oxidative stability. TG mainly is applied for the quantitative determination of major components of a polymer sample. TMA or DLTMA (dynamic load thermomechanical analysis) measures the elastic properties viz. modulus. 

Figure 11 Dynamic load thermomechanical analysis of a carbon fibre/epoxy resin beam measured in three point bending mode. The force steps between 0.5 and 1.5 N and hack every 12 s. Heating rate 5°C min in air...

As early as 1982, Riesen and Bartelst ] demonstrated the usefulness of dynamic load thermomechanical analysis (DLTMA) for the characterization of commercial joint sealants for building construction. They used DLTMA to study the viscoelastic behavior of four different sealant types polysulfide, polyurethane, silicone, and polyacrylate. The difference in viscoelastic behavior of the sealants can be seen from Fig. 8. 

Riesen, R., andBaitels, W., Rapid Quantitative Characterization of Elastomers by Dynamic Load Thermomechanical Analysis, in Proc. 7th Int. Conf. on Thermal Analysis, 2 1050-1056, John Wiley Sons, NY (1982)... 

Many physical and chemical processes are involved in the degradation of sealants and adhesives. Thermal analysis techniques have been used to characterize polymeric adhesives and sealant formulations and also to study the proeesses of degradation when they are exposed to natural elements. The applieation of techniques such as TG, DSC, DTG, Dynamic Mechanical Analysis, Dynamic Mechanical Thermal Analysis, Thermomechanical Analysis, and Dynamic Load Thermomechanical Analysis for such materials has been discussed in Ch. 14. 

Thermomechanical analysis (TMA) investigates the changes in the dimensions of a sample as a function of the temperature, for example shrinkage or extension of fibres." It is easier to work here with filaments than with staple fibres. Fibre composites and other materials are also analysed by dynamic loading. This dynamic mechanical analysis (DMA) enables, for example, the glass temperature of elastomers to be determined exactly. But in textile damage analysis TMA is seldom used. 

Half way between conventional thermomechanical analysis and dynamic mechanical analysis is the technique of dynamic force (or load) TMA. This method uses a standard TMA instrument but the force is changed between two values in a stepwise (or sometimes sinusoidal) fashion. The dimensional changes of the specimen are monitored as a function of time (and temperature) but no attempt is made to determine the modulus and damping properties of the material. 

A dilatometer (Latin dilatatio, an extension, and metmm, a measure) is an instrument to measure volume or length of a substance as a function of temperature. A summary description of the technique is given in Fig. 6.1. When one makes a volume or length measurement under tension or load, one applies the term thermomechanical analysis, abbreviated TMA, to the technique. Instrumentation and applications are described in Sects. 6.2-6.5. If the applied stress or the dimension of the substance varies as a function of time during measurement, the technique is caWeddynamicmadianicalanalysis, abbreviated DMA. Dynamic mechanical analysis has developed into such an important thermal analysis technique that a separate course of instruction is needed to do justice to the topic. Only a short summary is given in Sect. 6.6 to serve as an introduction to the field. 

Thermomechanical analysis (TMA) is a technique in which the deformation of a substance under a nonoscilla-tory load is measured as a function of temperature while the substance is subjected to a controlled temperature program. It is used extensively in polymer studies. The mode, as determined by the type of stress applied (compression, tension, flexture, or torsion), should always be noted. As already stated, dynamic mechanical analysis is a technique in which the viscoleastic response of a sample under an oscillatory stress is studied while the substance is subjected to a temperature regime. Torsional braid analysis is a particular case of dynamic thermomechanometry where the material is supported. 

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