Water-Based Polyurethane Dispersion (PUD) - Waterproofing Membranes

Polyurethane dispersions (PUD) consist of polyurethane particles dispersed in water with the aid of a dispersing agent added between the polymer chains. They are preferred in the automotive, construction, textile, packaging, recording and many other sectors because they are high-performance and environmentally friendly products. Their use is increasing day by day both nationally and internationally. This increase is a preference driven by performance considerations and legal requirements stemming from human and environmental health concerns. We will briefly clarify performance and cost issues related to PUD products and examine the resin and membrane products we offer for the construction sector.

Performance Approach

Polyurethane dispersion products first provide information about their performance through the raw materials used in the polymer chain. The choice of polyol type and isocyanate type is of great importance. The raw materials to be used impart different properties to PUD products, such as mechanical and chemical resistance. According to the types of polyols used, some properties of PUD products are shown in simplified form in the table below. In addition to the polymer structure, additional performance-enhancing additives are added to PUD systems. Various cross-linkers, adhesion promoters, surface modifiers, flame-retardant materials and touch-enhancing additives are some of these. Generally, PUD systems are evaluated in this manner within themselves. When compared to conventional polyurethanes, there are serious differences in terms of performance. The basic reason for this is that the product is synthesized at the nano scale. Water-based polyurethane systems generally have a particle size below 150 nm.

Cost Approach

As mentioned above, PUD systems are very important for manufacturers due to high performance and environmental factors, but their higher costs compared to conventional acrylic emulsions limit their use. For more economical costs and performance, use together with acrylics is preferred. This is done in two ways: 1) Physical mixing of PUD resins and acrylics by formulators or PUD resin manufacturers, 2) Incorporation of acrylics into the polymer chain during synthesis by PUD resin manufacturers. Through these and similar processes, PUD-based formulations can be made more economical with additional additives up to the level where price-performance is optimal. Of course, they will not have the same performance as pure PUD resins. With these processes carried out in many sectors, PUD usage is increasing. In areas where acrylic and other polymers alone are insufficient, PUD creates space for itself with its superior quality. At PURIN, with our investments in Turkey, we produce water-based polyurethanes using PUD technology and offer them to our customers at competitive prices. With these competitive prices, our customers can produce high-performance products without having to add other polymers to reduce costs.

Water Isolation Membranes

Water isolation work is the most critical issue determining the lifespan of a structure. The skeleton that holds structures upright is reinforced steel. Steel will rust where water is present and its performance will deteriorate. This weakening of the steel causes our buildings to collapse over time. For this reason, water isolation is the most performed work to extend the lifespan of buildings. Water isolation work is performed through certain water-repellent additives thrown into concrete, polyurethane injections used in cracks inside concrete, and liquid membranes applied by coating. In water isolation membranes, bitumen derivatives, acrylics and polyurethanes are mostly used. In terms of performance, polyurethane materials are far superior to other products. When examining polyurethane products, most commonly used are single-component, air-drying reactive polyurethane prepolymer-based filled materials. The reactive nature of these products brings both advantages and disadvantages. The most important advantage is the very high adhesion due to the ionic bonding it makes with the surface.

The disadvantages of polyurethane prepolymer-based isolation membranes are;

• Short shelf life, • Cannot be applied to damp surfaces, • Limited UV resistance, • Production difficulty for manufacturers, • Solvent content in the system. PURIN has been producing and supplying high-performance polyurethane prepolymer resins for water isolation membranes since its establishment in 2015. However, with our innovative approach and strong R&D experience, we have been producing water-based polyurethane dispersion (PUD) products using PUD technology since the beginning of 2018. We produce two different resins for flexible filled systems for water isolation and for hard transparent ceramic surfaces.

1) Flexible Water Isolation Membrane Resin:

This product is a polyether-based polyurethane dispersion resin. With its aliphatic structure, which can be converted into a membrane product through fillers and other additives added to the resin, it is a non-yellowing, flexible product. You can find some test results defining the resin below.

2) Hard Water Isolation Membrane:

Our other product is a transparent material for ceramic surfaces that we describe as hard elastic. Structurally it is a polycarbonate polyol-based aliphatic polyurethane dispersion. Unlike the previous one, this product is not intended for filler systems but is ready for direct use. With its transparent property, it preserves the visual appearance of ceramic and other surfaces applied to it. You can find some test results defining the product below.

We can summarize the advantages of water-based polyurethane dispersion isolation products over others as follows;

• High Mechanical Performance: It has much higher mechanical performance compared to non-polyurethane products. It has similar performance to polyurethane prepolymers, • High Chemical Performance: Very high hydrolysis resistance, does not decompose in aqueous environments, • Can Be Applied to Damp Surfaces: Polyurethane prepolymer-based systems are very sensitive to ground moisture. Application cannot be made to damp surfaces, but PUD membranes already contain water in their structure. For this reason, they can be easily applied to any type of damp or even wet surfaces, • UV Non-Yellowing: Most polyurethane prepolymer-based products are aromatic and UV-strengthening additives are used to delay yellowing, but yellowing will occur after a certain period. PUD membrane systems, on the other hand, are manufactured as aliphatic by their nature. For this reason, there is no yellowing problem, • Environmentally Friendly Product: Polyurethane prepolymer-based products contain flammable and volatile solvents. They present risks to the environment and human health. PUD membranes, being water-based systems, do not pose risks related to human and environmental health. • Production Ease: Production of polyurethane prepolymer-based products involves risks. Interaction of the product with moisture, increase in temperature and increase in reactivity, packaging, solvent-based system nature, shelf life and the stock costs of special additives required for production and their high costs are parameters that complicate production. In PUD membranes, the resin is water-based and non-reactive. For this reason, none of the above risks apply. Production is as easy as making a paint formula. • Long Shelf Life: Polyurethane prepolymer materials continue to react with moisture. When you add filler material into the prepolymer, the moisture coming from the filler must be eliminated. For this you need to use special chemicals. Despite this, the viscosity of reactive products increases over time in packaging and may even solidify in the package in cases where the necessary additives are not used. For this reason, since the resin in PUD membrane systems is not reactive, a long shelf life of 12-24 months can be obtained without requiring special additives. • Cost Advantage: Polyurethane prepolymer-based membrane products are generally aromatic and UV reinforcers are used. Considering the cost of this system and the stock costs of the special additives used, the cost of PUD membranes to manufacturers is in similar figures. Of course, the fact that PUD membranes are aliphatic presents a major advantage. When you use an aliphatic resin based on polyurethane prepolymers, PUD membrane costs will definitely be at a lower cost. In conclusion, PURIN continues to produce new and specialized products with polyurethane PUD technology. Sometimes designed by our technical team, sometimes developed according to the demands of our customers, our products add differentiation to the market. We design sustainable processes with our high-performance products with our sensitive approach to the environment and human health and providing cost advantage to our customers. With our national and international certifications, we offer our PUD products to Turkey and the countries of the region. Ibrahim Kecin Senior Chemist, M. Sc. General Manager PURIN Polyurethane Ayşenur Dede R&D Manager PURIN Polyurethane