**Preface to "Advanced Testing of Soft Polymer Materials"**

Manufacturers of soft polymer products, as well as suppliers and processors of polymers, raw materials, and compounds or blends are compelled to use predictive and advanced laboratory testing in their search for high-performance soft polymer materials for future applications. Ideally, predictive laboratory testing balances accuracy, relevance, instrument productivity and cost-effectiveness, while providing new mechanistic insights and opportunities for modelling the overall properties of materials and products. In this context, new concepts for soft polymer materials are of great importance, taking into account new trends in many modern technological fields. New advanced test methods and techniques will link to fundamental scientific principles, even showing how test results from individual pieces of uncured/cured elastomers or other soft polymers relate to real geometry and loading conditions of polymer parts, creating new opportunities to link laboratory test data from soft polymer materials to the real product performance. Furthermore, the rapid development of simulation tools offers great prospects for predicting the behaviour of soft polymer materials and their durability based on unique data sets obtained through new advanced testing methods, including the upcoming possibilities of artificial intelligence.

The collection of publications contained in this edition therefore presents different methods used to solve problems in the characterization of various phenomena in soft polymer materials.

This reprint presents recent research results (Lindemann et al.) on the evaluation of the effect of resin content on the glass transition of rubber compounds. Broadband dielectric spectroscopy (BDS) and fast differential scanning calorimetry (FDSC) are applied for the characterization of the dielectric and thermal relaxations as well as for the corresponding vitrification kinetics. The dielectric behaviour of rubber is currently receiving considerable scientific attention and effort. Therefore, the following two publications are devoted to this phenomenon. Aloui et al. experimentally investigated the effect of plasticizer polarity on the mechanical stability of the filler network using simultaneous mechanical and dielectric analysis, while Harea et al. studied the effect of local strain distribution on the effective electrical resistivity of carbon black-filled natural rubber, combining for the first time the digital image correlation (DIC) method with measurements of dielectric behavior under mechanical stress. The DIC method is a very effective tool for describing the strain fields or deformation of stressed bodies and Sotomayor-del-Moral et al. used this method very effectively to analyze the viscoelastic Poisson's ratio of different types of elastomers and also the thermal effect under creep loading. J-B. Le Cam presents a simple and fast approach to characterize the mechanical and energetic behavior of elastomers, i.e., how they consume the applied mechanical energy. The methodology consists of performing a single uniaxial cyclic tensile test with simultaneous temperature measurements, whereby the temperature measurements at the sample surface are processed using the thermal diffusion equation to reconstruct the heat source fields, which in effect amounts to surface calorimetry. The mechanical properties of elastomers are also the subject of research by Kyei-Manu et al. to study the effect of colloidal properties of carbon black on statically and dynamically loaded natural rubber. While standard test methods were used to characterize the properties under static loading, a torsion rheometer was used to describe the properties under dynamic cyclic loading. The effect of fillers on the various rubber properties is evident from the studies presented, where the basic filler is mainly carbon black. Their characteristics and properties have been studied in detail in many scientific papers. Carbon nanotubes are one of the very promising materials that have a significant positive effect on rubber properties. Therefore, Bakosov ˇ a and ´ Bakosov ˇ a studied the effect of reinforcement of rubber composites by carbon nanotubes, investigating ´ this phenomenon by atomic force microscopy (AFM), tensile tests, hardness tests and dynamic mechanical analysis (DMA). The mechanical properties of the rubber are achieved through the curing process, and therefore the process must be optimized to obtain a suitable rubber network. This topic has long been extensively addressed in the studies of Poschl et al., who presented two articles in the issue. The first publication deals with the rheometric evidence of the co-curing effect of bismaleimide in conjunction with accelerated sulphur on natural rubber and chloroprene rubber blends, both from a methodological and material point of view. The second publication deals with the identical topic, but in combination with different halogenated rubbers. Within both topics, rotational rheometers were used as a device to characterize the cure kinetics. Another type of curing is the effect of ultraviolet radiation. This issue is addressed in the study by Datta et al. and here the effect of ultraviolet radiation on rubber is characterized by determining basic mechanical properties, which are complemented by infrared spectroscopy, contact angle analysis and scanning electron microscopy analyses. Loos et al. investigated various elastomers in terms of their behaviour towards liquids such as moisture, fuels or fuel components. For this purpose, an analytical procedure using sorption experiments in combination with gas chromatography and mass spectrometry was presented, which is thus able to accurately analyse the swelling behaviour of the elastomers. Gejgus et al. introduced high-frequency ˇ dynamic stiffness measurements up to 3000 Hz on a newly developed test bench to characterize the rubber material in the context of the engine mounts.

Thus, the present volume provides a comprehensive overview of the recent developments in the field and will be of interest to both academic researchers and industrial professionals.

This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic—DKRVO (RP/CPS/2022/006).

> **Radek Stoˇcek, Gert Heinrich, and Reinhold Kipscholl** *Editors*
