Dynamic mechanical analysis advantages

A convenient method for determining transition times and transition temperatures of polymeric materials is dynamic mechanical analysis. One type of instrument which is particularly suitable for polymeric solids is the freely oscillating torsion pendulum (TP). Advantages of the TP include its simplicity, sensitivity, relatively low frequency ( 1 Hz) which permits direct correlation of transition temperatures with static nonmechanical methods (e.g., dilatometry and calorimetry), and its high resolution of transitions A major disadvantage of the conventional TP is that test temperatures are limited by the inability of materials to support their own weight near load-limiting transition temperatures. 

Thermal analysis methods can be broadly defined as analytical techniques that study the behaviour of materials as a function of temperature [1]. These are rapidly expanding in both breadth (number of thermal analysis-associated techniques) and in depth (increased applications). Conventional thermal analysis techniques include DSC, DTA, TGA, thermomechanical analysis, and dynamic mechanical analysis (DMA). Thermal analysis of a material can be either destructive or non-destructive, but in almost all cases subtle and dramatic changes accompany the introduction of thermal energy. Thermal analysis can offer advantages over other analytical techniques including variability with respect to application of thermal energy (step-wise, cyclic, continuous, etc.), small sample size, the material can be in any solid form - gel, liquid, glass, solid, ease of variability and control of sample preparation, ease and variability of atmosphere, it is relatively rapid, and instrumentation is moderately priced. Most often, thermal analysis data are used in conjunction with results from other techniques. 

Dynamic mechanical analysis in polymeric multiphase systems in solid state, as part of rheology, is associated with oscillatory tests that are employed to investigate all kinds of viscoelastic material from the point of view of flow and deformation behavior. In particular, it evaluates the molecular mobility in polymers, the pattern of which may be an indication of phase-separated systems. Although there are certain preferred tools for visual examination of phenomena for these kinds of systems, dynamic mechanical analysis has the advantage of examination in dynamic conditions and of the prediction of properties. 

There are two main types of mechanical thermal analysis instruments, namely thermomechanical analysis and dynamic mechanical analysis, TMA and DMA respectively. The first is a simple technique that has been available for many years and simply records change of sample length as a function of changing temperature. Despite this simplicity it enables the measurement of phase transitions, glass transition temperature and coefficient of thermal expansion. It has the advantage of being simple to use and perhaps more importantly the interpretation of results is quite straightforward. 

Today, FTIR forms the mainstay of analytical infrared instrumentation [96], All of the spectra presented in this chapter were produced on FTIR instrumentation. However, the older traditional dispersive instruments are still adequate for most polymer applications. FTIR offers some unique advantages in terms of sample handling, and as such is more versatile for polymer analysis. Applications that take full advantage of the properties of FTIR, which extend the capabilities of infrared spectroscopy for polymer characterization, include infrared microscopy, GC-IR (in the form of pyrolysis GC-IR), GPC-IR (gel permeation chromatography-IR combination), TGA-IR (thermal gravimetric analysis-IR combination), and step scan, for dynamic-mechanical property measurements. 

The discussion of the mechanisms and models of the relaxation process given in Section 2.5 shows that the application of time-resolved methods produces substantial advantages in accessing dynamical information, but it does not allow the complete pattern of the dynamic process to be obtained. The analysis of the experimental results requires that a particular dynamic model be assumed. Information on the dynamics is obtained from studies of the dependence of emission intensity on two parameters the frequency (or the wavelength) of emission and on time. The function 7(vem, t) may be investigated by two types of potentially equivalent experiments ... 

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