Fire-Resistant KimRIGID PIR Systems

Today, as in the rest of the world, fires break out in our living spaces in our country as a result of preventable or unpreventable factors. Due to rapid population growth, unplanned urbanization and rapid industrialization in our country, the number of fires occurring and material losses caused by fires are increasing day by day. It is a clear fact that a single spark can destroy all our efforts and hopes within minutes. Many countries have developed various directives to protect against fire. Based on these directives, the materials used in our structures must be fire-resistant [1]. In modern architectural structures, the use of traditional materials is being abandoned due to economic reasons and difficulties encountered during the construction phase. For these reasons, sandwich panels are being used as building construction materials due to their ease of use and economic viability. Sandwich panels are generally building construction materials that provide thermal insulation and mechanical strength, containing filler material of different types and thicknesses between aluminum or galvanized sheets.

Internal filler materials used in sandwich panels generally include polyurethane foam (PUR), polyisocyanurate foam (PIR), expanded polystyrene foam (EPS), extruded polystyrene rigid foam (XPS), stone wool and glass wool [2].Figure 1. Sandwich panel systems as building materials

Polyurethane foams are copolymers bonded together with urethane groups, produced by diisocyanates containing two or more –NCO groups and diols containing two or more –OH groups, expanded by chemical or physical means [3,4]. Polyisocyanurate foams (PIR); with their low thermal conductivity coefficient, high compressive strength and high dimensional stability, are being presented as future fire-resistant building materials. Polyisocyanurate foams are a more specialized type of polyurethane foam.

Figure 2. Chemical representation of polyurethane foam and polyisocyanurate foam structures

The difference between polyurethane foam (PUR) and polyisocyanurate foam (PIR) is that diisocyanate and diols are in stoichiometrically different ratios during the foam formation reaction phase. While the (NCO/OH) ratio in polyurethane foams is close to 1 or slightly above 1, in polyisocyanurate foams (PIR) this ratio is larger than in polyurethane foams and closer to 2. In short, polyisocyanurate foams contain a larger amount of diisocyanate molecules in the environment than would completely react stoichiometrically with the diols. The excess –NCO groups present in the environment react with each other through various trimerization catalysts to form isocyanurate structures. The cyclic isocyanurate blocks in the foam structure improve the fire-retardant properties of the foam [5,6,7].

Figure 3. Index ratios in polyurethane foam (PUR) and polyisocyanurate foam (PIR)

Generally, polyisocyanurate foam formulation includes; polyester polyol blends (–OH component), polymeric MDI (–NCO component), additives, trimerization catalyst blends and blowing agents. The good fire-retardant properties of polyisocyanurate foams are due to the isocyanurate and aromatic polyester polyol structures.

Figure 4. Polyisocyanurate foam (PIR) panel systems

Table 1. Fire classes, densities and thermal conductivity coefficient values of insulation materials used in sandwich panels

As the Kimteks Polyurethane family, we are increasing our research and development efforts every day to prepare innovative, economical and environmentally friendly products. As products of our company, KimRIGID PIR systems provide excellent solutions for sandwich panel manufacturers. KimRIGID PIR systems are specialized structures that provide higher fire resistance compared to PUR systems. Thanks to isocyanurate structures, the foam's resistance to flame increases during a fire. KimRIGID PIR systems are products with compressive strength values in the range of 130-150 kPa, densities of 38-42 g/ml, thermal conductivity coefficient of 21 mW/mK and fire resistance at a minimum level of B s2 d0 according to the European standard SBI (Single Burning Item).

Table 2. Reaction profile analysis and physical characterization of foams for Kimteks Polyurethane KIMrigid PIR systems

Dr. Emre Baştürk Head of Research and Development Rigid Systems Kimteks Poliüretan San. ve Tic. A.Ş.  

References 1. Market study flame retardants, http://www.ceresana.com/en/market-studies/additives/flame-retardants, 26 May 2016. 2. Flame Retardants, Specialty Chemicals Update Program, https://ihsmarkit.com/products/chemical-flame-retardants-scup.html, September 2017. 3. D.K. Chattopadhyay, Dean C. Webster, Thermal stability and flame retardancy of polyurethanes, Progress in Polymer Science, Volume 34, Issue 10, October 2009, Pages 1068-1133 4. Yao Yuan, Chao Ma, Yongqian Shi, Lei Song, Yuan Hu, Weizhao Hu, Highly-efficient reinforcement and flame retardancy of rigid polyurethane foam with phosphorus-containing additive and nitrogen-containing compound, Materials Chemistry and Physics, Volume 211, 1 June 2018, Pages 42-53. 5. J. Xu, T. Wu, C. Peng, S. Adegbite, Influence of acid and alkali pre-treatments on thermal degradation behaviour of polyisocyanurate foam and its carbon morphology, Polymer Degradation and Stability, Volume 141, (2017) Pages 104-118. 6. M. Kuranska, A. Prociak, U. Cabulis, M. Kirpluks, J. Ryszkowska, M. Auguscik, Innovative porous polyurethane-polyisocyanurate foams based on rapeseed oil and modified with expandable graphite, Industrial Crops and Products, Volume 95, (2017) Pages 316-323. 7. Ming-Jun Chen, Xu Wang , Mei-Cen Tao, Xing-Ya Liu, Zhi-Guo Liu, Yan Zhang, Cheng-Shou Zhao , Jun-Sheng Wang, Full substitution of petroleum-based polyols by phosphorus containing soy-based polyols for fabricating highly flame-retardant polyisocyanurate foams, Polymer Degradation and Stability, Volume 154, (2018) Pages 312-322.