Service Life of External Thermal Insulation Systems and the Effect of Redispersible Polymer Powders on Impact Resistance

In our country, as is the case worldwide, energy demand is increasing daily due to population growth, rising urbanization rates, and industrial development, and it is becoming increasingly difficult for our energy resources to meet these needs. For this reason, methods of using energy efficiently and controlling energy consumption have become a necessity rather than a trend being followed. A large portion of energy consumption consists of heating and cooling energy use in industry and residential buildings. One of the most important methods followed to carry out this consumption efficiently, create a healthy and comfortable living space, reduce fuel consumption, and protect buildings from internal and external effects while extending their lifespan is the use of external facade thermal insulation systems in buildings. External facade cladding systems with thermal transmission coefficients suitable for their purpose of use, whose primary objective is to prevent the formation of thermal bridges and ensure continuity of insulation, rank at the top of the most widely used thermal insulation systems in our country and worldwide. For thermal insulation systems to provide a long-lasting solution, not only the quality and properties of the thermal insulation material used but also the performance of the entire system must be considered. In our country, cement-based materials are at the forefront of thermal insulation systems. One of the leading reasons for the use of cement-based products in adhesive mortar used for bonding insulation boards to mineral surfaces and in plasters applied over insulation material, as well as in final coat mineral plasters, is that they are more cost-effective compared to acrylic-based plasters. For cement-based materials used in thermal insulation systems and thus for the entire system to demonstrate high performance and long-lasting durability, the use of polymers in the adhesives and plasters applied has now become a necessity.

When polymer is used by selecting the correct type and correct ratio, it will impart the following properties to thermal insulation systems:

• Increased adhesive strength of the thermal insulation board adhesive mortar to both mineral surfaces and thermal insulation boards; reduced water absorption by the system through water repellency; increased impact resistance of the system by providing significant elasticity

One of the most important characteristics determining the service life of external facade cladding systems is their impact resistance against external effects. The impact resistance of building external facade coatings is important not only in terms of performance and longevity but also for maintaining aesthetic integrity. The most striking example of this can be understood from the damage to building external facades during the hailstorm that occurred in Istanbul last July.  

Figure 1: Appearance of Thermal Insulation Systems Without Impact Resistance Following the Hailstorm That Occurred on 27 July 2017 in Anatolian Istanbul (Source: www.ensonhaber.com)

We can say that, in addition to polymers' properties of increasing the adhesive strength of cement-based materials and water repellency, the greatest benefit they provide is increasing the system's impact resistance. Impact resistance, which is the greatest handicap of cement-based materials against systems not containing cement, can be significantly improved as the amount of polymer used in the material increases. To observe this effect most clearly, it will be sufficient to perform impact resistance testing on plasters prepared with variable polymer ratios.

Figure 2: EN 13499 Impact Resistance TestTEST METHOD AND RESULTS:

The plaster mortar formula mentioned above was applied 4 mm thick together with mesh onto a standard EPS thermal insulation board. After 24 hours, a standard primer and external facade paint were applied over the plaster. After the system was cured under normal conditions for 28 days, a 10 J impact resistance test was performed in accordance with EN 13497 standard (a steel ball weighing 1 kg was dropped freely from a height of 105 cm, striking the surface perpendicularly).

Figure 3: Results of Impact Resistance Tests of Plasters Figure 4: Close-Up Views of Impact Resistance Test Containing Polymer in Different Ratios Results

As can be clearly seen from the test results, as the amount of polymer used in cement-based thermal insulation mortars was increased, impact resistance clearly improved.

In conclusion, the most critical point here is that when a polymer with appropriate chemical properties is used in the correct ratios, it increases the elasticity of the material in which it is used, enabling it both to tolerate thermal expansion stresses resulting from temperature differences and to demonstrate resistance to physical impacts from external effects, thereby providing significant protection against cracks and fissures that would otherwise occur in the structure.

The fundamental reason thermal insulation systems have rapidly become popular in our country has been the reduction of energy expenditure. However, to fully achieve this goal, thermal insulation systems must be durable and long-lasting.

At this point, greater awareness among consumers in the market is imperative, and it is unavoidable that end users inquire about the polymer ratios of the mortars used in thermal insulation systems they purchase to ensure these systems are durable and long-lasting.

Tamer Tezel / Technical Solutions Manager / Construction Solutions / Organic Chemistry