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Contact angle measurements, using the dynamic contact angle and Washburn methods, were taken for 100% aramid and viscose fabrics, as well as for 50:50 aramid and viscose mixed fabrics of different structure. Based on the measurements of contact angles wetted with hexane, water and formamide, the fabric surface free energy was calculated by means of three (Owens-Wendt, Wu and van Oss-Chaudhury-Good) theoretical models. The aim of the study was to analyze the usefulness of the dynamic contact angle and Washburn methods for assessing surface properties of textile materials, using selected measurement liquids, and to relate the results to the further investigation of actual wetting and penetration of model fabrics designed to protect against hazardous or irritant liquids. It was found that both methods are useful for determining the fabric surface free energy values; the Washburn method is characterized by the high practical value in assessing surface properties of textile materials, regardless of their structure, whereas the dynamic contact angle method allows for more thorough observation of how the fabric structure of the same raw material composition exerts its effect on the wettability and surface free energy value.

Textiles are characterized by a diversified and relatively high susceptibility to sorption of volatile substances and may influence indoor air quality. The aim of this study was investigation the susceptibility of fibers to sorption of two environmental tobacco smoke (ETS) markers: nicotine and 3-ethenylpyridine (3-EP) and changes in concentrations of these substances in fibers under light exposure. For this purpose, we used non-colored, natural and synthetic fibers, which had not been subjected to any modification. It was observed that nicotine as pure or as one of the ingredients of ETS was adsorbed on the surface of all of the used fibers, and cotton and polypropylene fibers adsorbed it more than other fibers. 3-EP (in ETS) was adsorbed by synthetic fibers and when we used high concentrations of 3-EP in the air it was adsorbed on the surface of cotton fibers in the presence of synthetic fibers. The greatest susceptibility for simultaneous sorption of nicotine and 3-EP (in ETS) was observed for polypropylene fibers. Results show that nicotine is a better marker for ETS contamination of textile materials than 3-EP.

The linear viscoelastic limit of poly(methyl methacrylate) (PMMA) is established on the basis of the Reiner‐Weissenberg criterion of strength. The obtained limit is not simply a “strainlimit” or a “stress‐limit” but a function of both strain and stress, an energetical limit. In stress‐strain representation the limit is independent of time and temperature, which means that the linear or non‐linear behavior of the material depends only on the actual values of strain and stress. Some experimental data obtained on PMMA confirm the theory.

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