Thermomechanical property measurement

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. 

Dynamic properties are more relevant than the more usual quasi-static stress-strain tests for any application where the dynamic response is important. For example, the dynamic modulus at low strain may not undergo the same proportionate change as the quasi-static tensile modulus. Dynamic properties are not measured as frequently as they should be simply because of high apparatus costs. However, the introduction of dynamic thermomechanical analysis (DMTA) has greatly widened the availability of dynamic property measurement. 

This article reviews recent developments in polymer thermomechanics both in theory and experiment. The first section is concerned with theories of thermomechanics of polymers both in rubbery and solid (glassy and crystalline) states with special emphasis on relationships following from the thermomechanical equations of state. In the second section, some of the methods of thermomechanical measurements are briefly described. The third section deals with the thermomechanics of molecular networks and rubberlike materials including such technically important materials as filled rubbers and block and graft copolymers. Some recent data on thermomechanical behaviour of bioelastomers are also described. In the fourth section, thermomechanics of solid polymers both in undrawn and drawn states are discussed with a special focus on the molecular and structural interpretation of thermomechanical experiments. The concluding remarks stress the progress in the understanding of the thermomechanical properties of polymers. 

Newly born, the scanning thermal microscopy derived from atomic force microscopy brings a revolution in the instrumentation for measuring thermophysical and thermomechanical properties of the matter, and the TA instrument was awarded at Pittsburg 1998. The instrument has been applied for the characterization of Ibuprofen compacts as model substance. ... 

Despite the disadvantages, the method has found general application with minor adjustments. In another variant, the specimens are heated under load to a certain holding temperature and deformation Is measured after removal from the furnace. Torsion methods are employed for more detailed investigation of the thermomechanical properties of refractories (e.g. Hennicke and Tomsu, 1970 Spicak, 1971 Staron, 1975). 

This chapter is the first in a series that will make the case that many of the important features of real materials are dictated in large measure by the presence of defects. Whether one s interest is the electronic and optical behavior of semiconductors or the creep resistance of alloys at high temperatures, it is largely the nature of the defects that populate the material that will determine both its subsequent temporal evolution and response to external stimuli of all sorts (e.g. stresses, electric fields, etc.). Eor the most part, we will not undertake an analysis of the widespread electronic implications of such defects. Rather, our primary charter will be to investigate the ways in which point, tine and wall defects impact the thermomechanical properties of materials. 

Based on the measured thermomechanical properties and the microstructure of the graded layer of TiC-NiaAl functionally graded material, using the analysis method, the interface residual thermal stress of TiC-NiyAl sphere in the sintering process was calculated. The relationship between the stress and the content of NiyAl was presented. The results show that the failure mechanics of TiC-NijAl composite may be different in different content of NiyAl. 

The theoretical stress levels for the three molding compounds A, B, and C are compared in Figure 3 based on the measurement of their thermomechanical properties and the calculation of the curvature for the bilayer beam structure. The low stress material C has the lowest calculated stress levels, while material A has stress levels that are comparable to those of material B. 

Since bilayer beam experiments after any number of THSK cycles were impossible, a comparison between strain gauge experiments and these bilayer beam experiments is only possible after molding. Based on the results presented above it can be concluded that strain gauge experiments correlate well with bilayer beam experiments, showing that low stress molding compounds can be characterized as such based on measurement of the fundamental thermomechanical properties that determine residual stresses. 

This discussion demonstrates how a logical rehnement of acceptable chemical formulation parameters against measured thermomechanical properties of the dried preparations will aid in the development of stable products. Thus, the often-repeated dictum, even by those who should know better, that acceptable products can only be obtained by trial-and-error methods is outdated and should be discarded. 

Properties relating to performance of completely cured adhesive were determined by mechanical spectroscopy and thermomechanical analysis. Measurement of glass transition temperature and coefficient of thermal expansion was obtained from temperature scanning. 

In addition, the thermomechanical properties of this region are not known, nor are they easily measured. The following questions still remain to be answered ... 

Torsion-braid analyzer n. An instrument which permits the measurement of thermomechanical properties of polymers that are undergoing structural changes during cure. Shah V (1998) Handbook of plastics testing technology. John Wiley and Sons, New York. 

A comprehensive thermodynamic investigation of ED/W mixtures was made recently by Huot et al. [44] but these authors performed measurements in a limited range of temperature (5 < t/°C 45) and, unfortunately, they overlooked some simple and informative thermomechanic properties, such as static relative permittivity e [46] and kinematic viscosity [11]. 

Vicat penetration is much more influenced by PLA crystallinity. In the case of PDLLA and amorphous PLLA, Vicat penetration values of 52-53°C and 59-60°C, respectively, were reported. Also these values are very near to the Tg of the polymers. On the other hand, crystalline PLLA presents a very different behavior, with values of 157-165°C. This marked difference in Vicat penetration measurements is related to the contribution of crystallinity to thermomechanical properties of this material at a microscopic level [2,7]. 

The thermal and thermomechanical properties of the polymer/HAp composites (glass transition temperature, melting and crystallization behaviour, thermal stability, crosslinking effects, phase composition, modulus, etc.) can be evaluated by thermal analysis methods, like TG, DSC and DMA. Recently, a modulated temperature DSC (MTDSC) technique has been developed that offers extended temperature profile capabilities by, for example, a sinusoidal wave superimposed on the normal linear temperature ramp [326]. The new capabilities of the MTDSC method in comparison with conventional DSC include separation of reversible and non-reversible thermal events, improved resolution of closely occurring and overlapping transitions, and increased sensitivity ofheat capacity measurements [92,327]. 

Polyurethane and UPR-hybrid IPN networks were studied by several authors [86-88]. The thermomechanical properties of the networks were investigated. Influence of hard domains on mechanical properties was the main factor studied [86]. DSC measurements were applied to evaluate the... 

This paper concerns the preparation and the thermomechanical properties of environmentally compatible polymers derived from saccharides and lignins at our laboratory. The above research results have been obtained over the last several years. The environmentally compatible polymers include polyurethane (PU) and poly(8-caprolactone) (PCL) derivatives. PU derivatives were prepared from saccharides and lignins. PCL derivatives were synthesized from lignins, saccharides, cellulose and cellulose acetate. The thermal properties of the above polymers were studied by differential scanning calorimetry (DSC), thermogravimetry (TG) and TG-Fourier transform-infrared spectrometry (FTIR). Mechanical properties were measured by mechanical testing. 

Polyurethane thermoplastic elastomers, like other segmented polyurethanes, are characterized by microphase separation into hard-segment microdomains and a soft-segment microphase, which is the cause for their versatile physical and thermomechanical properties. Considerable work has been devoted to introduce quantitative measures of the degree of microphase separation in... 

In a series of our studies, the presence of the microphase-separated structure in PAS film is effectively estimated from the EPMA measurement [10], the thermomechanical properties [14], the gas permeabilities [14] of PAS, and cell adhesion onto a PAS surface [15]. In addition, the results of the XPS and contact angle measurements suggest that PDMS components fully cover the outermost surface of the PAS film [10]. The appearance of the periodicity of the microphase-separated structures of PAS film, however, are still unclear. In this section, to clarify the bulk and surface structures visually, we observed the appearance of the microdomains of the bulk and that near the surface for the multiblock copolymer by means of transmission electron microscopy (TEM). 

Thermomechanical properties, such as tensile modulus and tan5, of photo-cured NOA 63 for various curing times were measured by DMA. The results are shown in Figure 3. DMA measurements were consistent... 

Thermal analysis helps in measuring the various physical properties of the polymers. In this technique, a polymer sample is subjected to a controlled temperature program in a specific atmosphere and properties are measured as a function of temperature. The controlled temperature program may involve either isothermal or linear rise or fall of temperature. The most common thermoanalytical techniques are (1) differential scanning analysis (DSC), (2) thermomechanical analysis (TMA), and (3) thermogravimetry (TG). 

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