Thermodilatometry

The deformation of the analyte, under the influence of an externally applied mechanical stress, is followed as a function of temperature. When the deformation of the sample is followed in the absence of an external load, the technique is identified as thermodilatometry. 

Thermodilatometry is a particular case of thermomechanical analysis in which change in a dimension is monitored as a function of temperature under negligible load and, normally, measures the linear coefficient of expansion. It has become the most usual method and there is an ISO standard for plastics5. A British standard is identical, published as BS ISO 11359-2. ASTM has a TMA method for materials in general6 and also a formal procedure for the calibration of the analysers7. The absence of methods specifically for rubber reflects the relatively small interest in the property in the industry. 

In thermomechanical analysis (TMA) the deformation of the sample under stress is monitored against time or temperature while the temperature increases or decreases proportionally to time. Changes are detected by mechanical, optical, or electrical transducers. The stress may be a compression, penetration, tension, flexure, or torsion. Generally the instruments are also able to measure the sample dimensions, a technique called thermodilatometry. The stress F/A) expressed in N/m or Pa may be a normal tensile stress cr, a tangential shearing stress x, or a pressure change Ap the force applied is F and A is the area. 

The sintering effect to the properties of silica adsorbent has been studied using silica gels synthesized from tetraethoxysilane and impregnated with various amounts of Na+ ion and heated in various atmospheres [24]. Figs. 8, 9, 10 and 11 show the change of specific surface area with the samples loaded with various amounts of Na+ impurity, and atmosphere, the thermogravimetry and the thermodilatometry of the sample with the... 

Thermodilatometry, in which the sample is exposed to a range of temperatures and changes in the physical dimensions of the sample recorded. 

Simultaneous thermodilatometry-electrical conductivity measurements have been employed to determine the sintering or coalescence of powdered materials. An equation has been developed by Ramanan and Chaklader (62) that relates electrical conductance to density changes of powder compacts on sintering ... 

Fig. 34.15 shows the thermal expansion of the RT-cured adhesives under several pressures measured using the bellows vessel. The adhesives expanded greatly, even though they had been cured. The maximum volume expansion under atmospheric pressure was about four-fold at 90 °C. Above 100 °C, it seems that volume increased again. However, the volume expansion was caused by leaked gas it was confirmed that the gas leaked from the specimen by thermodilatometry with the glass syringe (Fig. 34.4). Since the microcapsules in the adhesive were expanded about eight-fold, only 1-2 MPa of hydrostatic pressure was apphed from the microcapsules to the matrix resin, as shown by the intersection in Fig. 34.14.

Dynamic mechanical thermal analysis measures damping and dynamic moduli and is covered in Chapter 21. Thermal mechanical analysis measures deformation of a test piece. such as the dimensional change due to thermal expansion (also called thermodilatometry) and indentation at the softening point of the material. 

If the applied stress is negligible then the technique becomes that of thermodilatometry. This technique is used to determine the coefficient of thermal expansion of the specimen from the relationship ... 

The joint use of several thermal techniques enables us to solve more complex problems, e.g. to correlate through the study of TG, DTA and thermomechanical analysis (TMA) dehydration traces of zeolite Linde A and some of its cation-exchanged forms, the single recorded thermal eflFect with the removal of water molecules from a specific structural site [11, 12], or to find, through TG, DTA and thermodilatometry (TD) measurements, the structural relationships between cymrite (BaAl2Si208.H20) and hexagonal barium feldspar [13]. 

Standard Test Method for Constant-temperature Stability of Chemical Materials Standard Test Method for Arrhenius Kinetic Constants for Thermal Un.stable Materials Standard Test Method for Rapid Thermal Degradation of Solid Electrical Insulating Materials by Thermogravimetric Method Standard Test Method for Autoignition Temperature of Liquid Chemicals Standard Test Method for Specific Heat of Aircraft Turbine Lubricants by Thermal Analysis Standard Test Method for Linear Thermal Expansion of Solid Materials by Thermodilatometry... 

---