Photoacoustic measurement of thermal diffusivity of polymer foils

Abstract

The photoacoustic measurement of polymer foils, typically 170--200 pm thick, is discussed. It is shown that the measurement based upon the phase lag between the front and rear illuminations is applicable only in a limited range offrequencies from 6 to 12 Hz. The dominant mechanism responsible for the photoacoustic signal, in almost the entire frequency range 10-100 Hz, is proven to be the thermoelastic bending of the foil samples. The thermal diffusivity is then obtained from the frequency dependence of the front~phase illumination data.

Photoacoustic Monitoring of Internal Plastification in Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Copolymers: Measurements of Thermal Parameters

“…The magnitude of thermal parameters (Table 1) were in the range with the values quoted in the literature for polymers 16,[17][18][19] . There was also a consistent trend, suggesting that the values of the thermal parameters increase as the 3HV content increases and these values were larger than thermal parameters for a sample without 3HV.…”

“…However, for a plate shaped sample, the contribution to the PA signal from the thermoelastic bending of the sample cannot be neglected, especially for thermally thick samples as has been demonstrated by many authors. This effect is essentially due to the temperature gradient inside the sample along the z-axis 17,18 . Owing to the existence of this temperature gradient parallel to the z-axis, thermal expansion depends on z.…”

Thermal lens scanning of the glass transition in polymers

“…[1][2][3][4][5] The photothermal techniques are essentially based upon sensing the temperature fluctuation of a given sample due to nonradiative deexcitation processes following the absorption of modulated or pulsed light. Apart from having been extensively used in the optical and thermal characterization of a wide spectrum of materials, ranging from semiconductors 6 to glasses 7,8 and biological specimens, 9,10 a growing number of applications of these photothermal techniques have been used for investigating the different physicochemical properties of polymers, [11][12][13] as well as how the processing conditions [14][15][16][17] of these materials affect their physical properties. Despite this growing interest and the importance of the applications of these techniques to the polymer research area, so far the photothermal measurements have been carried out mostly at near room-temperature conditions.…”

Determination of Thermal and Sorption Properties of Poly-3-Hydroxy Octanoate Using Photothermal Methods

“…This effect is essentially due to the temperature gradient inside the sample along the z-axis [15,16]. Owing to the existence of this temperature gradient parallel to the z-axis, thermal expansion depends on z.…”