Polyurethane Systems for Smooth Surface Quality

Polyurethane systems are materials that facilitate modern life and are now used extensively in many sectors and integrated into our living spaces. Footwear systems, coatings, construction chemicals, automotive, furniture and textiles are the sectors with the highest consumption of polyurethane raw materials. In this article, we will provide information about how polyurethanes with improved surface tension offer us advantages in end products and where they can be applied. The effect resulting from the surface layer of a substance exhibiting properties resembling a flexible layer is called "surface tension." To explain this effect, we can cite the example of certain insects walking on water. Based on this, we can say that a contact angle forms at the point where the liquid contacts the surface. The magnitude of this angle, called the contact angle, depends on the relative magnitude of the attractive forces between the liquid's own molecules (cohesive forces) and the attractive forces between the liquid and solid (adhesive forces). The greater the magnitude of cohesive forces compared to the magnitude of adhesive forces, the greater the contact angle between the liquid and solid. In other words, a large contact angle indicates weak liquid-solid attractive forces, while a small contact angle indicates strong attractive forces. If the contact angle is less than 90°C, the liquid wets the container; if greater, it does not. If the angle formed between a liquid in a capillary and the capillary walls is less than 90°C, the liquid wets the capillary surface and a concave meniscus forms on the liquid surface. If the contact angle is greater than 90°C, the liquid does not wet the capillary and a convex meniscus forms. We conducted research to apply this chemical property of chemistry to other areas of polyurethane systems. We developed polyesters with a narrower molecular weight distribution and certain structural properties in terms of process characteristics. This polyester with low polydispersity (PDI= Mw/ Mn) has a more stable structure. In addition to this property, the free glycol ratio at a very low level creates added value for the product both physically and chemically. This structural stability ensures standard quality in the products our customers manufacture. In light of these properties achieved in the raw material, we found the opportunity to develop products that will create value for our business partners in the end product. We formulated our obtained polyesters in elastomer applications, coating systems and shoe sole systems. In the studies we conducted, we attempted to improve surface tension properties with the additives we used. With the modifications we made to the structure of our polyester and together with the additives used, we obtained products with water-repellent properties and smooth, uniform skin structure in sole systems. Our sole systems obtained with the polyesters we developed in these systems have very good surface quality compared to competing products, and another property arising from this becomes apparent in mechanical tests. In physical tests of the product, the first stage of durability is always the surface. The smoothness and homogeneity in surface structure here helps achieve very good results in many tests. The mechanical tests in which skin strength stands out are: • Flex test, • Tensile test, • Abrasion test. Additionally, besides sole systems, we also observe similar properties in polyurethane elastomer systems thanks to the polyesters we produce. The chemical structure of polyurethane elastomers consists of three fundamental building blocks. Elastomer is formed by the reaction of polyol, chain extender and isocyanate under specified ratios and conditions. While the urethane bonds resulting from the reaction of polyol and chain extender with isocyanate form the hard segment, the long polyol chain forms the soft segment. The ratio of hard segment/soft segment and the manner of their phase separation largely determine the final properties of the elastomer. The important element here is not only the reaction of these raw materials at the correct ratio and conditions, but also the selection of the correct raw materials. In elastomers, the desired high tear and tensile strength depends on the chain structure of the molecule. In this chain, the linear properties of polyol as well as the linear structure of isocyanate, Mw (molecular weight) and PDI (polydispersity) play important roles. With the polyesters we developed, polyurethane elastomers also exhibit a smoother surface and consequently better physical values in end products. Especially for parts prominent in the elastomer group, surface smoothness is important both cosmetically and, depending on the application, smoothness in parts such as squeeze rollers is very important for product performance. As in sole systems, surface quality here also results in better performance in physical tests. According to the results obtained: • Extremely high abrasion and tear resistance, • Low permanent deformation have been achieved. [caption id="attachment_99833" align="aligncenter"] polyurethane[/caption] As Kobe Poliüretan, our main objective will be to solve production-related problems experienced by our business partners and to develop products that create differentiation, enabling them to achieve the growth they deserve in the market. Eren Güz / Research and Development and Quality Control Manager - Kobe Poliüretan References • Croll SG and Skaja AD (2002) Spestroskopic Adsorption and Effective Dosage in Accelerated Weathering of a Polyester-Urethane Coating, Journal of Materials Science, 37, 4889-4900. • ISO 7724(1984) Paints and Varnishes – Colorimetry, International Organization for Standardization. • Nzokou P, Kamdem DP and Temiz A (2011) Effect of Accelerated Weathering on Discoloration and Roughness of Finished Ash Wood Surfaces in Comporasion with Red Oak and Hard Maple, Progr. in Org. Coatings, 71, 350-354. • I.R. Clemitson, Castable Polyurethane Elastomer • Michael Szycher, Szycher's Handbook of Polyurethanes • www.nanoprotect.co.uk