DMA242 C - Wide-ranging Applications

log (Frequency/Hz) With a multi-frequency measurement, frequencies beyond the measurable range of the DMA can beachieved by using the superposition method. Employing the Williams-Landel-Ferry (WLF) equation, e.g. E’ and tan Î´ values at a certain referencetemperature (here -20°C) can be extrapolated to 100,000 Hz .The influence of frequency is demonstrated with theexample of an SBR rubber mixture. As expected, with increasing frequency, the Tg (evaluated at 1 Hz) is shifted to a higher temperature and higher E’ values are obtained (multi-frequency measurement in the dual cantilever bending at 2 K/min). 140°C, the stiffness valuesare of the same magnitude as those for aluminium. Glass transition starts at 154°C (extrapolated onset).The E’’ peak (174°C) and tan Î´ valuesare accordingly lower. The tan Î´ peak (196°C) arealso characteristic values for the glass transition temperature. A 30% glass fiber-reinforced PBT (parallel and per-pendicular to the fiber orientation) was measured in the 3-point bending mode at 1 Hz and 2 K/min. Considerably higher values for the stiffness and theonset of the E’decrease (43°C) are obtained for the parallel-oriented type (straight line).The tan Î´ peaks are at thesame temperature. The single cantilever mode with a special sample fixtu-re in combination with a free pushrod is preferable for the determination of the bending modulus of metals. Presented in this figure is the modulus series of sheet- metal strips of steel, titanium, aluminium and magne- sium at room temperature and 1 Hz.The polyester fiber tested in the tension mode showsrelaxations in the low-temperature range, which can be evaluated as E’ onset, E’’ peak or tan Î´ peak.Glass transition starts at 75°C. The storage modulus decreased from approx. 4,200 MPa to 200 MPa. A carbon fiber-reinforced epoxy resin was measuredin the 3-point bending mode at 1 Hz and 3 K/min. Even at a temperature of 7