Citation: Kowalski, M.; Salerno-Kochan, R.; Kami ´ nska, I.; Cie´ slak, M. Quality and Quantity Assessment of the Water Repellent Properties of Functional Clothing Materials after Washing. Materials 2022, 15, 3825. https://doi.org/ 10.3390/ma15113825 Academic Editor: Jan Broda Received: 26 April 2022 Accepted: 24 May 2022 Published: 27 May 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article Quality and Quantity Assessment of the Water Repellent Properties of Functional Clothing Materials after Washing Mateusz Kowalski 1, * , Renata Salerno-Kochan 1 , Irena Kami ´ nska 2 and Malgorzata Cie´ slak 2 1 Department of Non-Food Product Quality and Safety, Cracow University of Economics, Rakowicka 27, 31-510 Cracow, Poland; salernor@uek.krakow.pl 2 Department of Chemical Textile Technologies, Lukasiewicz Research Network—Textile Research Institute, Brzezi ´ nska 5/15, 92-103 Lodz, Poland; irena.kaminska@iw.lukasiewicz.gov.pl (I.K.); malgorzata.cieslak@iw.lukasiewicz.gov.pl (M.C.) * Correspondence: kowalskm@uek.krakow.pl Abstract: The aim of the research was to evaluate the changes in the surface properties of five functional clothing materials with water-repellent finishes (including PFC-free finish) after 1, 5, and 10 washes with three detergents. A new approach to the interpretation of the water-repellent properties of textile materials is presented, based on two techniques, i.e., the spray test method and contact angle measurements. The results showed that washing materials with hydrophobic finishes can cause significant changes in their properties, which are mainly dependent on the composition and structure of the material, as well as the type of hydrophobic finish. The PFC-free finish is the least resistant to washing. For all materials with PFC finishes, the water repellency depends on the fluorine content on the surface and fabric topography. It was also found that increasing washing frequency resulted in a gradual decrease in water repellency. The loss of water repellency below an acceptable level (Grade 3) occurred after the fifth washing for all materials. Significant differences in the interpretation of the results of the spray test and contact angle measurements were observed. Using these methods separately provides information on the changes in the surface properties of the tested materials; however, their parallel application allows for obtaining complementary data, which is important for the proper interpretation of results. Keywords: hydrophobic textiles; spray test; water repellency; surface properties 1. Introduction One of the most important properties of the multifunctional textiles used in outerwear is water repellency. Along with resistance to water penetration (waterproofness) and water vapour permeability (breathability), it has a direct impact on the wearer’s comfort [1,2]. It is responsible for protecting against water soaking into the fabric, which, as demonstrated by Rengasamy [3], can lead to reduced breathability and deterioration of the garment’s thermal properties, causing an acceleration of the heat transfer process and, consequently, heat stress and severe discomfort for the garment wearer [4]. According to Lomax [5], wet clothing in contact with the skin can cause up to 25 times faster heat loss by conduction; so, the proper protection of outerwear against the effects of precipitation water is essential for providing the wearer with the desired physiological comfort. Water repellency properties in textiles can be achieved in a number of ways, using hydrophobic fibers, dense fabric structure, and chemical and/or physical surface modifica- tions [6,7]. In functional outerwear made of multilayer materials, the most widely used finishes are durable water repellents (DWR), whose role is to lower the surface free energy of the material and achieve water-repellent properties. The low surface energy of the mate- rial, which is lower than the surface tension of water, causes droplets to undergo a pearling phenomenon and be “repelled” from the surface [8,9]. Starting in the mid-20th century, Materials 2022, 15, 3825. https://doi.org/10.3390/ma15113825 https://www.mdpi.com/journal/materials