Nanotechnology Adhesives: Water-Based Polyurethanes

Adhesives are used in many sectors including textiles, technical textiles, footwear, leather, foam, sandpaper and EVA. Adhesives are formed by dissolving polymer-based resins in a solvent or through polymeric material synthesis within a solvent. As the molecular weight (length of the polymer) of the active material contained in adhesives increases, performance in terms of flexibility and durability improves. An increase in a material's molecular weight means an increase in its viscosity. Therefore, in polymer production, molecular weight is monitored during the process (during manufacturing) by measuring viscosity, and predetermined viscosity values are targeted. Because after production, the molecular weight distribution of the same product with similar viscosity values (providing a distribution according to synthesis steps) is determined more precisely in special equipment such as GPC (Gel Permeation Chromatography). While molecular weight, or viscosity, holds such an important position, we tend to prefer products with higher molecular weight in terms of performance, but high viscosity creates serious difficulties in application. For this reason, adhesives are offered with high solvent ratios. But what if this solvent is harmful and ventilation and protective equipment are insufficient in an operation... This is where we need to think beyond just producing a product! This should be our employees' health. Ventilation, mask use and other operational measures certainly should be in place, but this is not a sustainable production process. For your sustainable production processes, we should focus on the solvent component in your adhesives. As solutions: 1- Two-component products where no solvent is used, 2- Single-component adhesives used in melt form, 3- Adhesives where water is used as the solvent. Two-component products will not integrate easily into your operations. For adhesives used in melt form, very serious machinery investments will be required. Adhesives where water is used as the solvent and provide the highest performance are "Water-Based Polyurethanes". The most important advantage of water-based polyurethane materials is that very high molecular weight polymers can be obtained at very low viscosity. This property allows us to use them at higher solids content and in all types of applications.

For example, when comparing solvent-based and water-based polyurethane resins with the same solids content; when resin synthesis is performed with DMF and water, which are the most polar solvents, the viscosity of the solvent-based resin is 100,000 mPas, while the viscosity of the resin produced with PUD technology is only 50 mPas.

When you consider that these two resins have the same performance, you will see that PUD products provide a significant advantage in terms of ease of application. Water-based polyurethanes can be synthesized at low viscosity because they are nanotechnology products. Due to the production process, polyurethane synthesis is carried out in water and is nano-sized. Through raw material selection, stoichiometric calculations or process modifications, it is possible to obtain products in the desired nano size. The nano-sized synthesis of polyurethane resin provides it with low viscosity. The particle size analysis results of our most frequently produced PUD 101 and PUD 201 coded PUD resins are 47.3 nm and 50.8 nm with quite good homogeneity at approximately 0.2 polydispersity. Water-based products are obtained at low viscosity and can be brought to the desired viscosity with thickeners added afterwards. Spray application, knife application and roller application are possible with necessary viscosity adjustments. The obtained PUD adhesives can be easily used in many applications such as felt-foam, foam-textile, paper-paper, sandpaper-abrasive sand and shoe insole bonding.

Water-based adhesive is brought to a viscosity suitable for spray application and is used in shoe insole production for foam-to-textile lamination and especially for leather lamination (*).

In conclusion, water-based polyurethane (PUD) technology is quite different from conventional production methods. This different technology brings it significant advantages both in terms of performance and environment. As PURIN Polyurethane, with the PUD resin production we started at the beginning of 2018, we have established our position in many different sectors and aim to increase the number of our sectors and applications. We supply PUD products domestically and internationally based on water-based polyurethane coatings and adhesives. We expect these products, which attract more interest in the foreign market, to take their deserved place in our country as well, and we are trying to clarify their necessities. Let us remember that; incorporating change into the present rather than leaving it for the future will provide the opportunity to be the one followed rather than the one following. Reference * Application images were taken at Akform Insole - Karabük facility.