Testing and analysis methods at the KAP

Microscopic techniques offer specific examination options for plastics analysis, not only as part of research and development activities but also in particular for damage analysis and quality assurance. They include:

• Determination of material properties
• Identification of processing defects for evaluating part quality
• Fractographic examinations
• 3D-visualised surface quantifications
• Description of internal stresses and orientations with a polarisation microscope
• Evaluation of the design characteristics of a component
• Quantification of the amount and distribution of fillers and reinforcing materials, pores and multi-phase systems
• Volume-based component measurements and structural examinations

The microscopic preparation and analysis processes available at IKV cover the entire range that is of relevance for plastics analysis, with a view to obtaining meaningful results quickly and reliably. Of key importance here is the preparation of the specimen. The Institute possesses a broad knowledge base for obtaining reliable test results within the shortest possible time due, not least, to its day-to-day involvement in public research projects and the time it spends dealing with wide-ranging questions from industry.

Mechanical testing is an important tool for product testing and quality assurance. To describe the mechanical properties of construction materials, testing methods such as tensile tests, notched flexural impact testing and hardness testing are fundamental and frequently used methods. The deployment of universal testing machines allows both standardised testing processes and individual component tests.

As examples, here are some of the test methods carried in our laboratories in the course of accelerated testing:

• Tensile, compression, flexural tests
• Torsion pendulum tests, shear tests
• Crack expansion tests, tear propagation tests
• Bonding strength tests
• Friction tests
• Determination of compression set

Additional external influences on the plastic such as climate and media have to be taken into account at the test planning stage and when preparing the specimens. The mechanical tests are frequently preceded by sample preparation, ageing by UV radiation and weathering in conditioning cabinets.

Furthermore, some areas of the laboratory are ideally equipped for various long-time and dynamic tests. Throughout the laboratory, testing is carried out on thermoplastics thermosets and fibre composites. 

Knowledge of the flow behaviour of plastic melts and rubber or silicone materials and information on the viscosity of resin systems is essential to be able to accurately design the processing processes. Apart from determining the actual viscosity, it is also possible to measure their elastic and viscous proportions. This yields, for example, important information on the extent to which a plastic melt reacts to shear loads through a rise in temperature. Since the viscosity of a plastic is the product of many individual properties (molecular weight distribution, degree of branching, additives), it is also possible with rheometric methods to detect batch fluctuations on a comparative basis.

The following properties can be described with the aid of rheometric tests:

• Viscosity as a function of temperature, shear rate and pressure
• Elastic / ideal viscous proportions of the viscosity
• Pseudoplasticity
• Determination of Carreau parameters
• Storage modulus and loss modulus as a function of temperature and shear rate
• Change in a molecular structure (e.g. through degradation or crosslinkage)
• Change in the additive content
• Gel point and/or pot life of a resin system

Especially oscillatory measurements offer a large number of possibilities for describing materials. For this, preliminary trials are necessary to find a suitable individual operating point of the interaction system between rheometer and material.