PIR Systems

Polyurethane is a polymer chain composed of urethane groups formed as a result of the reaction between polyol and isocyanate. These types of polymers are also classified as thermoset plastics. Due to their great diversity and the numerous advantages they provide, they are used in many areas of our daily lives, from automotive to white goods, furniture to the footwear sector.

Polyisocyanurate, on the other hand, is a molecule with an aromatic structure formed as a result of the reaction of isocyanates with one another.

In 2017, the global polyurethane market size was calculated at USD 60.5 billion. This figure corresponds to 9% of the global plastics market. 67% of polyurethane consumed is in foam form. The entire market size is expected to reach USD 79 billion by 2021. [1]

Today, rigid PU foam is used in many different applications including construction and the white goods sector due to its very significant advantages.

• • High thermal insulation properties (19-24 mW/mK), • Lightweight and easy to use, • Resistance and dimensional stability at low and high service temperatures (-40°C, +90°C), • Fire resistance adjustable.

The above properties make polyurethane and/or polyisocyanurate foams ideal filling material for sandwich panel production, particularly for the construction of industrial buildings. If comparison with other filling materials is needed, they can be simply classified in the table below. [2] Rigid polyurethane foam formation begins with the reaction of polyol and isocyanate. This reaction is exothermic. With the reaction, temperature can rise to 120-140°C. As temperature increases, the gas in the polyol transitions from liquid form back to gas phase and, upon being trapped within the cells, creates foam. The foam formed consists of approximately 97% of cell gases by volume. The insulation properties of rigid polyurethane foam stem from these low thermal conductivity gases contained within the cells.

The polymer matrix surrounding the gases determines the physical and chemical properties of the rigid foam.

Many various side reactions occur during foam formation. In addition to the polyol and isocyanate reaction, components such as isocyanate with water and isocyanate with isocyanate also react with themselves. [3] In rigid foam formation, appropriate catalysts must be used so that the desired reactions are more dominant. Catalysts lower the activation energy of the relevant reactions, allowing those reactions to be more predominant. For example, if we want the reaction between water and isocyanate to proceed more readily, a blowing catalyst or a gel catalyst can be used for urethane reaction. In PIR systems, since the reaction between isocyanate and isocyanate must occur, the most important catalysts are metal catalysts called isocyanurate or trimerization catalysts. Using appropriate and correct amounts of trimerization catalyst is very important to produce a high level of PIR molecules. Fire resistance of rigid polyurethane foam can be increased basically by two simple methods. The first method is adding flame retardant additives, either halogenated or halogen-free, to the foam. Such additives will increase the material's fire resistance and reduce flame spread and smoke emission. The second method increases the foam's inherent fire resistance through polyisocyanurate molecules in rigid polyurethane foam.

While polyurethane material can withstand temperatures up to 260°C, polyisocyanurate molecules can withstand up to 380°C.

In case of a fire, indoor temperature in a building can reach up to 1,000°C. PIR systems emit similarly to other materials. During combustion, primarily CO and CO2 are released along with some toxic gases. The table below shows details of gases emitted during fire by polyurethane and some other materials. [4] To measure the performance of structural elements used in fire against fire, two different tests are generally conducted. The first is the material's reaction to flame and the second is fire resistance. For these tests, different standards and test methods may be used depending on the market. Kimteks Polyurethane has developed PIR systems for sandwich panel production in the construction sector that can be used in 4 or 5-component lines for panel production. HC (n-pentane) is recommended as the blowing agent. Our developed PIR system is suitable for panel production in various thicknesses from 40mm to 200mm. With the special trimerization catalyst package in its formulation, maximum PIR molecules can be obtained. With its low viscosity, homogeneous mixture and pure raw materials, it is suitable for easy and stable production in summer and winter months.   Emrah Akbaş Research and Development Manager Kimteks Polyurethane Industry and Trade Inc.             References [1] Nuno V. G, A.Ferreira, A.B.Timmons (2018). Polyurethane Foams: Past, Present, and Future, 2, 2-35 [2] D. SCHUTZ, J. SEO (2015). COMPOSITE INSULATED PANELS (CIPS) OR INSULATED SANDWICH PANELS, 2,2-6 [3] Dr. M. Kapps (2004). The production of rigid polyurethane foam [4] Japan Urethane Industry Institute (2009). Q & A on Fire and Fire Prevention of Rigid Polyurethane Foam