Unlike thermoplastics, metals, and rubbers, thermoset polyurethanes offer product designers the option to design what they envision without compromise. Through custom formulations, thermoset polyurethanes can have little to no water absorption compared to other known materials. To learn more about this high-strength material, click here, to download our Durethane ® technical data sheets. Durethane ® G provides longer component life and reduced maintenance requirements even in highly corrosive environments. For example, Durethane ® G has become a standard material for many mission-critical marine applications, due to its extremely low absorption rate and unique properties. By employing engineered thermoset polyurethanes, the rate of water absorption can be specified to fit the needs of your application. Product designers are now seeking alternative materials to avoid stiffness, durometer, and dimensional changes when exposed to water. Designing with Water AbsorptionĪlthough some thermoplastics, metal, rubber, and other natural materials can absorb water overtime - this can still be highly disadvantageous to many applications. Applications that are generally submerged in water or experience high humidity often require low water absorption to maintain the parts mechanical and physical properties. However, generally speaking, unlike metals, plastics, rubber and other natural materials - thermoset polyurethanes can be customized to repel most water without the effects of swelling, oxidizing or corroding. Water Absorption Compared to Other MaterialsĪs previously discussed, polyurethanes come in many forms including solids and foam, which display differing levels of water absorption. However, consistent results are often achieved utilizing the ASTM-Standard D570 test. Generally, results will vary depending on the type of polymer, additives, temperature, and length of exposure. This method typically consists of a week-long process, comparing wet weight to dry weight. Water absorption values are often measured by the percentage of weight gain. If you want to learn more about the adaptability of polyurethane foams, click here. For example, open cell foam has tiny, breathable air pockets which allow water to permeate the material, whereas the cellular structure of closed cell foam does not allow water to easily flow through. The more porous the material, the quicker the part will retain water. Water absorption is typically determined by the amount of water that penetrates a material. In this post, we will further explain water absorption is and how it can play a role in your product's design. Depending on the physical properties and material, thermoset polyurethanes can practically have zero water absorption compared to other known materials. There are several factors that make some polyurethanes more absorbent than others. Neither silicon nor fluorine hydrogen bonds with water molecules, and the treated fabric thus repels water.The short answer is yes, to a certain degree. Most treatments use silicon compounds, but the Scotchgard process uses fluorine chemicals. Fabrics are made waterproof by chemically blocking the hydroxyl groups so that they can no longer hydrogen bond. This is also why synthetic fibers dry much more quickly than cotton. Polyester, which has few hydroxyl groups, cannot hydrogen bond and so absorbs far less water. Although cotton doesn’t dissolve in water, it can hydrogen bond to water molecules and thus hold on to them tightly, removing them from your skin. Cotton is a naturally occurring polymer of cellulose which, like sugar, has many hydroxyl groups. Oil, in contrast, has none and cannot dissolve. Sugar molecules, for example, contain many hydroxyl groups that can hydrogen bond to water molecules, so it dissolves in water easily. It is essentially the same phenomenon that explains why oil and water don’t mix. Q: Why does a cotton towel absorb water better than one made of polyester or other synthetic fabrics?Ī: Cotton’s ability to absorb water has to do with a phenomenon called hydrogen bonding, according to chemists Kerry Karukstis and Gerald Van Hecke of Harvey Mudd College.
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