DMA Measurements in Humid Atmospheres

In UserCom 36 we announced the acquisition of Triton Technology Ltd. (www.triton-technology.co.uk). This acquisition has allowed us to expand our range of instruments for dynamic mechanical analysis (DMA). The TT DMA and DMA 1 are excellent choices both for standard DMA applications and for quality control. In addition, they offer two new options. First, there is the possibility of performing measurements under conditions of controlled relative humidity by equipping the instruments with a humidity chamber and coupling it to a humidity generator. Second, there is the fluid bath option, which allows you to measure a sample immersed in a liquid.

Introduction

When a material is immersed in a liquid, it can soften, react (harden) or dissolve. The liquid can affect a material to such an extent that it breaks, deforms or can no longer be used for a particular application. Figure 1 shows the TT DMA with the fluid bath option in the open and closed position.

Figure 2 shows the effect of water on a polyamide sewing thread measured by DMA in the tension mode. The thread was 10 mm long and had a diameter of 0.15 mm. The measurement mode used was “Ratio tension” with a value of 1.5, which corresponds to 150%, and a displacement of 0.20 mm.

The elastic modulus (E') was first measured in air. The thread was then immersed in water at 20 °C at a time marked by the vertical dashed blue line in Figure 2.

The experiment was repeated at 40 °C using a new thread. The curves show that the thread softens in water and that the water temperature influences softening. The elastic modulus decreased from 4.5 GPa to less than 1.3 GPa...

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Summary

The effect of liquids or the relative humidity on the mechanical properties of materials can be now be investigated using the TT DMA equipped with the “fluid bath” or the “humidity” options.

This means that a material can be tested in its actual application environment, for example in salt water, gasoline, oil, or in humid atmospheres. Relative humidity affects the production, storage and applicability of materials.

DMA measurements under conditions of controlled relative humidity have many important applications in research and development in the pharmaceuticals, plastics, chemicals, foodstuffs and other industries.

DMA Measurements in Humid Atmospheres | Thermal Analysis Application No. UC366 | Application published in METTLER TOLEDO Thermal Analysis UserCom 36