Stone Binder

Floor systems are a product category that continuously evolves with visual and technical requirements and that we walk on and come into contact with every day. In this article, we will discuss floor systems made with natural stone and the polyurethane binders used.

First, let us explain the floor system;

The system is obtained by mixing tumbled stones (generally 4-8 mm in diameter; stones of 1 mm or smaller are used in interior applications) with a binder, and then applying it to the ground using a trowel and guide. Whether the stones are tumbled or non-tumbled and the size of the stone diameter vary entirely according to preference. While visual designs come to the forefront in the preference for these floor systems, the most important reasons are the technical properties that the product provides. These properties are briefly as follows;

Provides high mechanical strength. (Image 1)

•It has higher mechanical strength compared to asphalt and similar systems, •Impact resistance is high, •It is resistant to heavy loads.

Image 1. Parking lot

It is a permeable system and does not retain water on the surface. (Image 2)

•Does not frost on the surface, •Ensures road safety, •Reduces salt use for de-icing, •Facilitates groundwater collection.

Image 2.

General Properties

• UV resistant depending on the binder, • Does not moss, • Does not retain mud, • Resistant to moisture and humidity, • Does not spread flame, • Compatible with both interior and exterior applications. (Image 3)

Image 3. Interior and exterior

Following the application areas briefly mentioned above, it is worthwhile to examine the binder materials used in this system. The purpose in these systems is to ensure that stones adhere to each other and do not separate under environmental conditions. Initially, two-component epoxy materials were used in these systems. Epoxy binders raised the need for different types of products due to the following problems: •Vulnerability to UV radiation and yellowing in light-colored stone systems, •Cracks in stone coatings due to hot-cold transitions or water freezing in winter. As in many other sectors, polyurethane materials are the best equivalent to epoxy materials. Polyurethane materials are products with desired hardness/elasticity designs, UV-resistant due to their aliphatic system/non-yellowing properties, and breathable due to their polymer structure. Let us explain why polyurethane materials should be preferred in this application area; There is no yellowing in aliphatic polyurethane materials; they are UV resistant. Our aliphatic products do not contain aromatic portions in their structure and are therefore not affected by UV radiation and do not yellow. The fundamental reason for yellowing is the interaction of aromatic structures with UV radiation and their transformation into a yellowing structure. Aromatic compounds are compounds composed of benzene and condensed benzene rings. In light of this information, when we look at epoxy and the well-known polyurethane isocyanate MDI compounds, we see that both structures contain aromatic portions. Therefore, for a non-yellowing structure, our raw materials must first not contain aromatic regions. In this sense, our basic polyurethane materials, polyol and isocyanate, being aliphatic in structure means. Considering that polyol groups are generally aliphatic in structure, aliphatic isocyanates are listed below.

Provides high mechanical strength.

Mechanical strength is one of the most important properties of polymer materials. Within the scope of our subject, we can explain it as follows. The greater the tensile strength of a product, the higher the strength with which the binder will hold the stones used. Epoxy materials can be rigid in structure, but they are not products with as high adhesion strength as polyurethanes. Single-component or two-component polyurethane materials have higher adhesion performance. The reason for this is that polyurethane materials bond to the surface and to each other with additional bonds. This bonding is characterized as hydrogen bonding. This bonding provides additional strength to the structure. This adhesion performance and mechanical strength in the final product prevent the ground from breaking during hot and cold transitions and when water trapped in stones freezes in winter. Better drainage capability. Stone floor systems, referred to as permeable floors, use their structural voids to allow water to pass to the bottom without retaining it on the surface. This system has enabled its use in areas with high water absorption, roads, and poolsides.

To design this system, stones of different sizes can be used or it can be achieved through polymer materials used as binders. The surface wetting capability of epoxy materials is not as good as polyurethane materials. Surface wetting capability directly affects adhesion.

The image above shows the contact angles of a liquid with a surface. If the angle between the liquid and the surface is less than 90°C (C), it wets the surface and explains better adhesion. If the contact angle is greater than 90°C (A), it does not wet the surface and indicates weaker adhesion. Because epoxy materials have less wetting capability, a minimum of 10% is used in the stone system to achieve adequate adhesion performance. In contrast, polyurethane materials are used at a rate of 4-5% due to their better wetting capability. Of course, these ratios are given for stones of similar size. This usage ratio provides both cost advantage and, due to less polymer material between stones in similar structures, allows for greater water drainage. With better water drainage, there will be no water accumulation on the surface. In this way, by preventing frosting on the surface, it will enable safer driving on roads. It reduces the use of salt and other substances for road frosting. High resistance to seawater and chemicals. Since the product contains no solvents, it can be easily used in interior spaces. As PURiN, based on our polyurethane expertise, we offer three different products for this application: aliphatic single-component, aliphatic two-component, and aromatic single-component. As a domestic manufacturer, while we reduce your costs to half that of epoxy in our aromatic product, we can offer you aliphatic (non-yellowing) systems equivalent to your epoxy costs. Our aim is to provide the polyurethane resins we produce to the domestic market with both price advantage and high quality, reducing dependence on foreign sources. Compared to products sourced from abroad, we provide advantages in price, delivery time (2-3 days), packaging options, your revision requests, and one-to-one technical support through our expertise in polyurethane. İbrahim Kecin Senior Chemist General Manager PURiN Polyurethane   Ayşenur Dede R&D Manager PURiN Polyurethane     Sources 1) Diisocyanates and Polyisocyanates," CEH Marketing Research Report (SRI), 2009