Dilatometry, volume-, length

The basic functions of state of TMA and dilatometry are length, volume, stress, and pressure, as pointed out in Figs. 2.16-2.17. For DMA, time must be added as explicit variable of the measurements. 

Dilatometry TD Length or volume change Creep, thermal expansion... 

This concludes the discussion of thermometry and dilatometry. The tools to measure temperature, length, and volume have now been analyzed. The tools for measurement of heat, the central theme of this book, will take the next three sections and deal with calorimetry, differential scanning calorimetry, and temperature-modulated calorimetry. The mechanical properties which involve dilatometry of systems exposed to different and changing forces, ate summarized in Sect. 4.5. The measurement of the final basic variable of state, mass, is treated in Sect. 4.6 which deals with thermogravimetry. 

The simplest volume recovery experiment performed is the down-jump. In this experiment, a material initially above Tg and at equilibrium is subjected to a temperature down-jump to an aging temperature Ta below Tg. The isothermal evolution of volume at T, as indicated by the downward arrow in Figure 1, is monitored with time via length or volume dilatometry. Figure 2 shows tjq)i-cal data replotted from Kovacs data (9) for a series of aging temperatures for poly(vinyl acetate). These curves, called intrinsic isotherms, are plotted as the relative departure from equilibrium 5 versus the logarithm of time, with S defined as... 

Three other thermal analysis techniques involve the basic measurement of length or volume and are called thermomechanical analysis (TMA) and dilatometry, respectively. Both techniques are described in Chapter 6, together with a brief survey of dynamic mechanical analysis (DMA). 

The connection between mass and volume, and thus also length, was the most difficult branch of metrology. Hundreds of units have been described, each pointing to a different method of dilatometry. Once one establishes the basic unit, which today is naturally the SI unit meter (see Fig. 2.16), measurement involves precise subdivision and comparison. 

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