WACKER VINNEVA®: A Boost Effect for Bitumen Coatings

Bitumen serves as a binder in asphalt and is found almost everywhere. Bitumen also functions as a waterproofing material on roofs and walls. For this purpose, products modified with polymers that are more flexible and therefore more resistant to mechanical effects are frequently used.

With the VINNEVA® product, Munich-based chemical company WACKER is launching a new product group for polymer-modified bitumen emulsions this year. Polymers enable coatings to adhere to building materials with extraordinary quality for extended periods. They also strengthen the barrier effect against water infiltrating from basement walls or other parts of buildings. Bitumen obtained from crude oil through vacuum distillation in refineries worldwide is subsequently used, for example, in road construction or as a waterproofing material in buildings. In Europe and North America, these coatings are mostly polymer-modified, meaning they contain polymers that improve the property profile. In other parts of the world, they are predominantly used without polymer additives. However, the polymer-modified bitumen market is expanding: According to a study conducted by Global Market Insights, total sector sales amounted to approximately USD 9.5 billion in 2016. Market researchers forecast an average annual growth rate of 4 percent through 2024. WACKER has developed binders based on vinyl acetate-ethylene (VAE) copolymers specifically for bitumen emulsions. With the product group introduced under the VINNEVA® name at two leading trade shows this spring (Middle East Coatings Show and European Coatings Show 2019), WACKER aims to acquaint users of unmodified bitumen emulsions with the benefits provided by polymer additives. Polymers make coatings more flexible and more resistant to all types of mechanical stress. On the other hand, VINNEVA® bitumen emulsions have some additional advantages compared to polymers previously used in bitumen emulsions. These are predominantly rubber-like substances such as styrene-butadiene rubber (SBR) and polychloroprenes.

Excellent Adhesion to Building Materials

Used in very small percentages depending on the formulation, VINNEVA® increases bitumen performance tremendously and, so to speak, elevates it to the Champions League of waterproofing materials. Particularly in terms of tensile adhesion strength and barrier effect against water, the performance of formulations modified with VINNEVA® is far superior to other modified bitumen emulsions. Comprehensive testing conducted in WACKER laboratories shows that tensile adhesion strength is up to 60 percent higher compared to conventional bitumen emulsions. To test tensile adhesion strength, the bitumen emulsion is first applied to a concrete slab. After it dries, circular test surfaces are cut from the coated slab. A metal test specimen is bonded to each of these surfaces. The force required to pull the test specimen along with the attached bitumen coating from the concrete is then measured. The more difficult it becomes to remove the coatings from the building material and the better the coatings adhere, the greater the force required.

Higher Resistance to Water Pressure

The most important function of a bitumen coating is to protect basements, roofs, or entire buildings against water infiltration. To test how well a coating performs this function, technicians apply the coating to small concrete cubes and allow them to dry under specified climate conditions. The coated cubes are then exposed to adjustable water pressure in a special system, for example for 24 hours. After this period, they measure whether a "loss" has occurred, meaning water has entered the concrete cubes in the original amount used. In such tests, bitumen emulsions with VINNEVA® additives have been shown to withstand higher pressure compared to coatings modified with conventional polymers. In addition, VINNEVA®-modified bitumen emulsions have other properties. In one example formulation, drying took 3.5 hours. In an otherwise identical formulation where a different additive was used instead of the VINNEVA® component, the drying process took 4.5 hours. Furthermore, the new polymer-based drying coatings are less tacky than many other systems. Shorter drying time in most cases means increased efficiency for the end user and thus savings in application costs of the bitumen emulsion.

Two Pathways for Polymer Modification

It must always be borne in mind that the properties of a bitumen emulsion depend not only on the polymer used but also on the bitumen composition and the additives employed. Bitumen is a mixture composed of heterocyclic compounds, aromatic polycyclic and branched hydrocarbons of varying saturation. Depending on the source of the crude oil, the proportions of these compounds in the bitumen vary considerably. For coatings, bitumen emulsions containing additives are produced from hot bitumen and water in colloidal mills. There are two ways to modify bitumen coatings with a VINNEVA® polymer: The polymer can be added to the water jet before emulsion formation or added to the bitumen emulsion afterwards. For this reason, WACKER designs VINNEVA® polymers specifically for each customer according to the bitumen composition and additives. Experts at WACKER Technical Centers worldwide provide support in this regard. In this way, coatings can be formulated that are superior to other polymer-based products in terms of important properties such as elasticity, elongation at break, and water impermeability. VINNEVA® polymers are based not only on petroleum but also on natural gas. As a result, their prices show less long-term fluctuation compared to other polymers used in bitumen modification. Additionally, unlike some other additives, they do not contain chlorine.

Also Suitable for Two-Component Systems

VINNEVA® polymers also make it possible to improve fiber-reinforced or filled bitumen coatings. The polymers are also particularly suitable for optimizing two-component systems common in Europe. These systems consist of a liquid component (polymer-modified bitumen emulsion) and a powder formulation containing cement and fillers. They are particularly suitable for application in thick layers.

Conclusion

VINNEVA® polymers improve the properties of bitumen-based building coatings. Coatings adhere very well to concrete and walls especially thanks to the new polymers. Additionally, bitumen modified with VINNEVA® protects roofs or basements against water infiltration, for example.

Image 1. Connections: WACKER dispersion is added to conventional bitumen emulsion (Photo: Wacker Chemie AG) Right: In WACKER's application laboratory climate chamber, the flexibility of polymer-modified bitumen emulsion at low temperatures is tested (Photo: Wacker Chemie AG)

Image 2. Crack bridging test: Polymer-modified bitumen emulsion must resist cracking in concrete substrate under stress (Photo: Wacker Chemie AG)Image 3. Tensile adhesion strength test: Thanks to polymer modification, tensile adhesion strength has increased by 60 percent compared to conventional bitumen emulsions (Photo: Wacker Chemie AG)

Dr. Markus Busold Strategic Marketing Manager Consumer and Industrial Polymers WACKER