Equipment | materials testing
Testing equipment manufacturers are exploiting the benefits offered by the latest electronic advances to keep pace with developments in plastics materials testing and qualification, writes Peter Mapleston
Putting plastics to the test
As plastics continue to develop and move into previously uncharted application areas, new test methods are being developed to keep up with changing require- ments. Meanwhile, suppliers of already well proven test equipment for assessing properties such as tensile strength are also treating their products with face-lifts that benefit from the latest advances in electronics – very often with the aim of simplifying use and/or presenting results in a more digestible way. This article takes a look at some of the most recent developments. Thermal conductivity is one of the more challenging
plastics properties to measure. However, instrument maker C-Therm says the patented sensor technology used in its TCi Thermal Conductivity Analyzer makes the process simpler and more accessible. “With the C-Therm TCi there is no complex regression analysis necessary as with other transient methods,” the company says. “No special sample preparation is required and there is no need to measure additional sample material properties such as heat capacity.” The TCi is provided with one versatile sensor for
testing all types of materials, whether they be solids, liquids, powders and pastes. A second sensor can be added for increased capacity. The instrument employs what C-Therm calls the Modified Transient Plane Source (MTPS) technique. The one-sided, interfacial
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heat reflectance sensor applies a constant heat source to the sample and thermal conductivity and effusivity (heat penetration coefficient) are measured directly, providing a detailed overview of the thermal character- istics of the sample. During the test, a known current is applied to the
sensor’s spiral heating element, providing a small amount of heat. The sensor’s guard ring is simultane- ously fired, supporting a one-dimensional heat exchange between the primary sensor coil and the sample. The current applied to the coil results in a rise in temperature at the interface between the sensor and sample, which induces a change in the voltage drop of the sensor element. The increase in temperature is monitored with the
sensor’s voltage and is used to determine the thermo- physical properties of the sample. The thermal conductivity is inversely proportional to the rate of increase in the sensor voltage (or temperature in- crease). The voltage rise will be steeper for lower thermal conductivity materials (for example a foam) and flatter for higher thermal conductivity materials (such as metal). Results are reported in real-time making thermal conductivity measurement fast and easy, according to the company. C-Therm says the main advantage the technique
September 2016 | COMPOUNDING WORLD 45
Main image: Anton Paar’s Solid Rectan- gular Fixture (SRF) for
rheological
characterisa- tion of solid rectangular bars is
designed to
enable fast test changeovers
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