Micro Test Specimens for Compound Engineering with Minimum Material Needs

Abstract

The use of micro test specimens is a good way to characterize micro injection molding processes and the resulting material properties. The material properties of microparts may differ from standard injection molding parts, due to an overrepresentation of the surface layers with high fiber orientation and divergent morphology. In order to characterize the distribution and agglomeration of fibers and particles for the manufacturing of micro injection molding parts of functionalized polymer compounds, it is essential to manufacture the test specimens and the part using the same process. The distribution and size of these particles e.g. Carbon-Nano-Tubes (CNT) or piezo ceramic particles is dependent on the polymer plastication process during injection molding. Therefore the use of micro test specimens is a requirement for precise material selection and engineering.Due to the minimum material needs, micro test specimens are also useful for the comparison of the material properties of new polymers and compounds, which were produced in amounts of 20 g to 100 g. Another application is the testing of highly elastic and ductile materials with strains over 100%. By using micro test specimens it is possible to test high strains with low elongations in a short time.A new innovative micro test specimen has been developed at the Technische Universität Chemnitz in cooperation with the Kunststoff-Zentrum in Leipzig, that is especially designed for the testing and dimensioning of plastic microparts with weights less than 0.1 g. The main feature of the new specimen and testing process is the combined positive and force-fitted locking, which enables a precise positioning of the micro specimen and an even application of the clamping force. In order to achieve reproducible clamping, testing and handling of the sample, the clamping and testing process are spatially separated. The shape of the test specimen enables a parameter optimization for the micro injection molding process.

Polypropylene Based Piezo Ceramic Compounds for Micro Injection Molded Sensors

“…The mechanical properties (tensile modulus, tensile strength and mechanical strain) were determined in a tensile test of specimen type A using a special clamping and positioning device (Fig. 2) [10]. As mentioned above, the sensor effect requires a high filling level of PZT but is limited by processability.…”

“…The cycle time appoints for how long the melt lasts in the hot cylinder of the injection molding machine. This time span has a high influence on the thermal degradation of the plastic melt and the mechanical properties of the molded part [10]. The test results of the thermodynamic model show, that the Peltier element based tempering system is as fast as a conventional hybrid tempering system.…”

An adaptable flexural test fixture for miniaturised polymer specimens

“…Constraints of tensile and flexural microtesters and of mechanical analysers (e.g. dynamic and thermomechanical) include the requirements for specific specimen shapes, significant specimen gripping challenges, limited force and displacement range, and the need for specialised equipment accessories to test in different environmental conditions [2,3]. The literature summarised in Table 1 reports examples of different approaches to develop test fixtures and methods for simple geometries of miniature specimens of polymeric materials to investigate mechanical behaviour, using specimens with characteristic dimensions of �15 mm.…”