Component properties

Stress-crack failure is one of the most common causes of damage in plastic components. The failure life of plastic components can be significantly reduced due to the combined effects of stresses caused by external loads or internal stresses, as well as stress-crack-promoting media.

In addition to evaluating stress crack resistance according to standardized test procedures, we focus on predicting failure times using accelerated testing methods.

Focus on:

• Accelerated testing methods for slow crack growth in polyolefins such as polyethylene and polypropylene
• The influence of various media and operating conditions, including manufacturing-induced residual stresses, on stress crack failure
   

Contact: 
Britta Gerets | +49 931 4104-575 | b.gerets@skz.de
Dr. rer. nat. Mirko Wenzel | +49 931 4104-347 | m.wenzel@skz.de

Plastic products are subject to continuous aging during use, which can be triggered by various factors such as elevated temperatures, UV radiation, or contact with chemical media. The nature and rate of these aging processes depend not only on the plastic used (polymer type, stabilizer system) but also, to a significant extent, on the specific operating and environmental conditions of the component. Appropriate accelerated testing concepts are therefore necessary for a reliable estimation of the expected service life.

At SKZ, we investigate the aging behavior of a wide variety of plastic components under realistic stress conditions, such as under the influence of temperature, in chemical media, or under simulated weather conditions. In addition to service life estimation using accelerated aging tests, a particular focus is placed on the application and further development of testing methods that can specifically characterize the current state of aging and material-relevant damage mechanisms.

Focus on:

• Thermo-oxidative aging (temperature, oxygen/oxidizing agents)
• Weathering behavior (radiation, temperature, and humidity)
• Media resistance (e.g., hot water, cleaning agents, oils)
• Time-lapse testing methods for predicting aging behavior
   

Contact: 
Dr. rer. nat. Mirko Wenzel | +49 931 4104-347 | m.wenzel@skz.de
Britta Gerets | +49 931 4104-575 | b.gerets@skz.de

The properties of plastic components depend not only on the chemical molecular structure of the polymer, but also on its morphology and residual stress state. 

Depending on the processing method, various factors—including flow and cooling conditions—give rise to different

• crystalline structures (degree of crystallinity, crystal modifications, superstructures),
• orientation states (molecular and fiber orientations that lead to anisotropic properties)
• and residual stress states.

It is often necessary to determine these and classify them with regard to component- or application-specific issues. This can be done with the aim of avoiding negative effects or utilizing them in a targeted manner.

Focus on:

• Morphological analyses (amorphous or crystalline structures, molecular and fiber orientations, weld lines or flow lines, structures of additively manufactured parts, impurities, defects, etc.)
• Systematic examination of processing influences and process parameters

Contact: 
Britta Gerets | +49 931 4104-575 | b.gerets@skz.de
Dr.-Ing. Kurt Engelsing | +49 931 4104-147 | k.engelsing@skz.de

Plastic components are subject to increasingly stringent requirements regarding their service life, while at the same time the development cycles for new products are becoming ever shorter. This often presents manufacturers and users of plastic components with the challenge of having to make reliable predictions about the expected maximum service life of their products. In some cases, the required minimum service life can easily be 50 years or more (plastic pipes or plastic sealing membranes are examples here). Even extrapolations based on long-term tests (typically lasting several months) are no longer sufficient to derive reliable predictions over longer periods.

For this reason, accelerated testing methods based on physically and chemically grounded models are of great interest, as they allow for reliable conclusions about the long-term and aging behavior of plastics to be reached within a shorter time frame. It is of central importance that accelerating the test, e.g., by increasing the temperature, does not lead to a change in the failure mechanism that would not occur at all in practice (under operating conditions).

The application and further development of methods for accelerated testing and service life prediction of plastic components represent an important focus of our R&D activities.
We conduct investigations for you to assess the condition of aged plastic components and to predict the service life of plastic components in new condition or after many years of use.

Focus on:

• Condition assessment using innovative testing and analysis methods
• Accelerated testing methods tailored to the respective failure mechanism (e.g., creep or thermo-oxidative aging)
• Use of physicochemical predictive models for service life estimation (e.g., Arrhenius, WLF, or Eyring models—tailored to the material and failure mechanism)
   

Contact: 
Dr.-Ing. Kurt Engelsing | +49 931 4104-147 | k.engelsing@skz.de 
Dr. rer. nat. Mirko Wenzel | +49 931 4104-347 | m.wenzel@skz.de​​​​​​​ 

Computer-aided methods such as the finite element method (FEM) enable the efficient design and analysis of plastic and composite components. By appropriately modeling material and component behavior, time, material, and costs can be saved as early as the initial development phase.

A meaningful simulation requires the best possible understanding of real-world material behavior, which depends primarily on the operating conditions (loads, temperature, humidity/media, etc.). Thanks to our extensive testing capabilities and decades of experience in the field of plastics engineering, we are able to incorporate all influencing factors (anisotropy, type and duration of loading, temperature, environmental conditions, etc.) into suitable simulation models. We would be happy to support you with our expertise on your project.

To the area simulation