Abstract-Ageing Condition Determination of Bonded Joints by Terahertz Spectroscopy

Jochen Taiber, Martin Kahlmeyer, Andreas Winkel, Eva-Maria Stübling, Fatima Taleb, Mikhail Mikerov, Stefan Sommer, Stefan Böhm, Martin Koch

https://www.springerprofessional.de/en/ageing-condition-determination-of-bonded-joints-by-terahertz-spe/18206724

The understanding of ageing processes in the field of adhesion technology is of utmost importance for long-term durable bonded joints. Environmental factors such as moisture, heat and UV radiation negatively affect the characteristics of adherends, adhesives and their interfaces and thus the overall bond performance over time. However, the evaluation of the precise ageing condition of adhesive joints remains challenging by means of well-established non-destructive testing (NDT) methods like shearography or thermography. Recently, it has been shown that terahertz (THz) time-domain spectroscopy is well suited as an NDT approach to study adhesive bonds. Specialized data extraction schemes enable the contact-free determination of the refractive index and the absorption coefficient from such measurements. The presented work wants to give an overview on the developments in the application of THz spectroscopy for the ageing condition determination of bonded joints, including the correlation between THz refractive index/absorption and the physical, chemical and mechanical property changes of adherends and adhesives due to ageing, the determination of THz specific values of adhesive joints by means of a reflection setup, the suitability of peak-to-peak amplitude evaluation, and THz imaging

Abstract-Terahertz Time-Domain Spectroscopy of Plasticized Poly(vinyl chloride)

Stefan Sommer, Martin Koch, Alina Adams,

https://pubs.acs.org/doi/abs/10.1021/acs.analchem.7b04548

Poly(vinyl chloride) (PVC) is today one of the most important commodity polymers. Its broad range of applications is due to the presence of plasticizers whose concentration largely impacts the microscopic and the macroscopic properties. Quantifying the concentration of plasticizer in PVC products is therefore of fundamental importance. Thus, in this paper, the applicability of terahertz (THz) time-domain spectroscopy for the characterization of plasticized PVC is for the first time evaluated in a systematic way. It could be demonstrated that the method is able to distinguish between PVC samples with different types and concentrations of plasticizers. Furthermore, a simple, fast, and efficient method is introduced to quantify the concentration of plasticizer in PVC samples of known plasticizer type but different thermal histories. The presented results are of key importance due to the need of reliable non-invasive and non-destructive analytical methods which can deliver onsite information about the remaining plasticizer concentration inside PVC products. Furthermore, it is expected that the proposed approach can be easily extended to other plasticized polymers.