BS ISO 6721-11:2019 pdf download – Plastics – Determination of dynamic mechanical properties- Part 11: Glass transition temperature.
The test procedure described minimizes errors of the specimen temperature through due to the thermal lag, which varies with the heating rate used, assuming that the specimen temperature is given by the measured oven temperature. NOTE 1 The temperature of the peak in the loss modulus curve correlates quite well with the midpoint of the storage modulus curve drawn in linear scale. For many thermoplastic materials, this temperature measured at a frequency of 1 Hz correlates well with the glass transition temperature determined as midpoint of step changes obtained in DSC curves measured at 20 K/min[3]. NOTE 2 The temperature of the inflection point in the storage modulus curve depends on the numeric representation of the storage modulus. Using a linear scale results in inflection points that are similar to glass transition temperatures obtained by DSC while plotting the storage modulus in logarithmic scale yields significantly higher values. NOTE3 The temperature of the peak in the curve of loss factor (tan delta) is influenced by the decrease of the storage modulus and thus usually higher than that of the peak in the loss modulus curve[3]. NOTE 4 In addition to the three methods above, the onset temperatures as defined by the intercept of the tangents below Tg and the slopes in the curves of loss modulus or loss factor (tan delta) or the decrease in the storage modulus, respectively, are also used[4].
5 Apparatus 5.1 Test equipment The test equipment shall be capable of heating at rates from 1 K/min to 10 K/min over the required temperature range and mechanically oscillating the specimen at the reference frequency of 1 Hz or 10 Hz, respectively. The heating rate accuracy shall be +5 % or better. The instrument shall continuously monitor and record the sinusoidal load applied to the specimen, the corresponding sinusoidal displacement, and the phase angle as a function of the measured temperature, in order to determine the storage modulus, loss modulus and loss factor. The load and displacement capabilities of the equipment shall be sufficient for the specimens tested. The temperature sensor should be positioned in the instrument as closely as possible to the sample under test, but ensuring it is not touching it. The equipment shall be calibrated regularly, or when the testing mode or atmosphere is changed or when the temperature sensor is moved or changed. 5.2 Devices for measuring test specimen dimensions These shall be in accordance with ISO 6721-1.