Dynamic mechanical multi-talent for visco-elastic properties

DMA 242 C - Dynamic mechanical Analyzer

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DMA 242 C - versatile applications

The influence of frequency is demonstrated with the example of an SBR rubber mixture. As expected, with increasing frequency, the T_g (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).

With a multi-frequency measurement, frequencies beyond the measurable range of the DMA can be achieved by using the superposition method. Employing the Williams-Landel-Ferry (WLF) equation, values such as E' and tanδ can be extrapolated to 100.000 Hz at a certain reference temperature (here -20°C).

A 30% glass fiber-reinforced PBT (parallel and perpendicular 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 the onset of the E'-decrease (43°C) are obtained for the parallel-oriented type (solid line). The tanδ values are accordingly lower. The tanδ peaks are at the same temperature.

The polyester fiber tested in the tension mode shows relaxations in the low-temperature range, which can be evaluated at E' onset, E'' peak or tanδ peak. Glass transition starts at 75°C. The storage modulus decreased from approx. 4,200 MPa to 200 MPa.

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