Flexible Polyurethane Foam for High Comfort

Flexible polyurethane (PUR) foams are open-cell copolymers bonded together with urethane groups, produced from diisocyanates containing two or more –NCO groups and diols containing two or more –OH groups, foamed through chemical or physical methods. [1] Flexible polyurethane foam synthesis was first carried out in the laboratory in 1941, with serial production beginning in 1954 in Germany. The first flexible PUR foam production utilized aromatic isocyanates (TDI&MDI) with polyester polyols. However, the synthesized foams exhibited low resistance to temperature and humidity conditions, frequently encountering problems such as crumbling and degradation. In 1957, the shift to polyether polyol use began to produce higher-performance foams. The use of polyether polyol provided the foam with higher hydrolysis resistance, greater comfort, and longer service life. In 1958, the use of new-generation catalysts and surfactants together with polyether polyols enabled both discontinuous production of flexible PUR foams and substantially improved their mechanical properties. [2] These developments led to the emergence of "high resillient" (HR) PUR foams, which recover quickly.

Figure 1. Index values in flexible polyurethane (PUR) foam

The comfort, ergonomics and other functions provided by HR PUR foams due to their high mechanical properties have made them unrivaled in many applications and widely used.

Figure 2. Applications of flexible PUR foams [2]

Two fundamental reactions exist in PUR foam synthesis: 1- Blowing Reaction

Figure 3. Chemical representation of blowing reaction [2]

The blowing reaction produces CO_2(g) and urea structures. CO_2(g) provides foam expansion, while urea structures play a role in the foam acquiring mechanical properties. [2]

Figure 4. Schematic representation of urea structures [2]

2- Polymerization Reaction

Figure 5. Chemical representation of polymerization reaction [2]

The polymerization reaction produces urethane groups and gives the foam its primary character.

Figure 6. Two and three-dimensional representations of flexible polyurethane foam structure [2]

Figure 7. Appearance of HR PUR foam structure under microscope [2]

The blowing reaction begins before the polymerization reaction but proceeds simultaneously. The relative rate of these two reactions is critical for obtaining a foam with desired properties. If the relative rate of these two reactions is not adjusted correctly, problems such as foam shrinkage and collapse are encountered. [2]

Figure 8. Polymer modulus over time graph [2]

HR PUR foams possess low permanent deformation, high elongation percentage and tensile strength along with high tear resistance values, making them one of the most comfortable, ergonomic and durable products.

Figure 9. Automotive seat produced with HR PUR foam [3]

As the Kimteks Poliüretan family, our R&D activities are increasing day by day to prepare innovative, economical and environmentally friendly products. Our company's MDI-based two-component KIMflex FC – Izokim FC HR PUR foam systems provide excellent solutions for the market. Our products serve the automotive seat and parts, office chair, sound insulation and medical product markets. When designing our products, we operate with a tailor-made approach, taking into account the conditions of the relevant markets, the conditions of the relevant geographies and the requirements of relevant certifications. In this context, for example, while designing freeze-resistant prepolymer systems for geographies with harsh climate conditions, we designed polyol blends without phase separation for customers without mixers. In addition, product certification is highly important in today's market. In this regard, all of our products used especially in the automotive sector are certified according to product specifications. In this regard, our products' certifications are as follows:

Table 1. Certifications held by KIMflex FC – Izokim FC systems serving the Kimteks Poliüretan automotive market [4,5]

The KIMflex FC 046 – Izokim FC 015 system, the latest member of the Kimteks Poliüretan HR PUR foam family, has been introduced to the market with a wide working ratio range (P/I, 100/55 – 100/75), early cure characteristics, high mechanical and flow properties, seamless operation under demanding process conditions, glossy finish and exceptional feel. The ability to operate in a wide ratio range enables the achievement of required hardness and permanent deformation values critical for office chair, automotive seat and medical product markets.

Table 2. Reaction profile analysis and physical characterization of foam for Kimteks Poliüretan KIMflex FC 046- Izokim FC 015 system

Ümit Ünal R&D Manager Flexible Foam Systems-Case Kimteks Poliüretan San. ve Tic. A.Ş.

References [1] 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 [2] Ron Herrington, Kathy Hock vd., Flexible Polyurethane Foams (The Dow Chemical Company,1997) [3] http://www.atssynthetic.com.pk/products/chemical-division/pakthane-polyurethane/polyurethane-automotive-industry/ [4] http://gcs-lab.com/tr/flammability_tests.html [5] http://www.sercovam.com/liste-essai.html#Renault D423109