What is Polyurethane (PU)? Where is Polyurethane Material Used?

The chemistry of urethane began to be discovered in 1849. During those years, Wurtz and Hoffman discovered a reaction involving isocyanate and hydroxyl compounds. In 1937, Dr. Otto Bayer adapted this reaction for commercial use. And before this process, nylon, which was preferred for use in the industrial world, gradually began to give way to polyester-based urethane polymers. With the start of World War II, the decreased use of basic materials such as rubber due to resource limitations enabled the development of polyurethane material for fibers, foams, and coatings.

Today, polyurethanes, which are used in the production of many products in our living spaces and constitute one of the most important polymer classes, form a polymer group containing diisocyanate and diol groups in various proportions and combinations in their structures. The reason why polyurethane material is the most preferred polymer group is that it is obtained from liquid monomers through an easy process requiring low energy. Additionally, it forms a wide range of products from soft, linear elastomers to rigid thermoset foams.

What is Polyurethane (PU)?

Polyurethane material is formed by reacting a polyol with a diisocyanate in the presence of appropriate catalysts and additives.

Component A: Polyol Component B: Isocyanate

Polyol: It is a mixture of polyether or polyester-based polyols, along with catalysts, silicone, colorants, blowing agents, and other chemicals added in appropriate proportions. These mixtures carry free hydroxyl (OH) groups.

Isocyanate: These are chemicals that carry free NCO and undergo an exothermic reaction when mixed with the polyol system. Isocyanates are recognized and named according to the number of NCO they carry.

What is Polyurethane (PU) Foam, Why is it Used?

Polyurethane foam is obtained by mixing polyurethane systems in specific proportions. This material is used to provide high levels of thermal, sound, or water insulation.

What are the Types of Polyurethane Foam?

There are many different types of polyurethane foams according to properties such as hardness, flexibility, and surface texture. Its ability to be produced in desired forms and dimensions has enabled it to have a very wide application area. Polyurethane foams are structurally divided into rigid polyurethane foams, flexible polyurethane foams, semi-rigid polyurethane foams, elastomeric polyurethane foams, spray polyurethane foams, etc.

Where is Polyurethane Used in Different Sectors?

Construction and Insulation Sector

Polyurethane is mainly used in buildings and structures to provide thermal insulation. Thanks to its thermal insulation and air impermeability properties, it traps heat in the environment. It is produced as sheets, sandwich panels, and pipe sections, or used as spray polyurethane foam by spraying method at the construction site.

Furniture Sector

Polyurethane is frequently preferred in the furniture sector thanks to its properties such as longevity, easy formability, paintability, lightness, and ease of application. While HR (High Resilience) polyurethane foams from the flexible polyurethane foam family are used in office chair production, visco (memory) polyurethane foams are used in mattress and pillow production, and rigid polyurethane foams are used in the production of wood imitation decoration products.

Automotive Sector

The main reasons for the increasing share of polyurethane use in the automotive sector are: low-cost part production and assembly, lightweight, impact resistance, ability to produce with different properties according to application location, flexibility property, and corrosion resistance. Especially integral polyurethane foams from the polyurethane foam family are used in the production of steering wheels, armrests, consoles, bumpers, etc.

Heating and Cooling Sector

Polyurethane is used in boilers and solar energy panels in the heating sector; and in industrial and domestic refrigerators (freezers), cold rooms, and refrigerated cases in the cooling sector to provide thermal insulation.

General Properties of Polyurethane

Impact Resistance

Polyurethane’s impact resistance is exceptional even at low temperatures, thus offering resistance against cracking, tearing, breaking, and swelling.

Temperature Resistance

Polyurethanes can withstand a wide range of temperatures and thus maintain their original shape and physical properties even in the most challenging conditions. Standard thermoset polyurethanes can withstand temperatures from -26°C to 93°C.

Thermal Conductivity Value

Thermal conductivity refers to a material’s ability to transfer or conduct heat. The thermal conductivity value, also known as the lambda value, defines a product’s insulation capacity based on the material’s heat permeability level.

Water Vapor Diffusion Resistance

The water vapor diffusion resistance factor is the ratio of air’s water vapor permeability to the sample’s water vapor permeability.

Dimensional Stability

Polyurethane exhibits excellent dimensional stability due to its thermoset structure. The dimensional stability of polyurethane varies according to the temperature environment.

Fire Resistance

Polyurethanes have the ability to offer enhanced fire resistance through special formulations. Thanks to their unique chemical structures, polyurethanes can meet the most challenging flame resistance requirements.

Applications of Polyurethane

• Flexible foam form: Most commonly used in home furnishings such as furniture, bedding, and carpet underlayment
• Rigid foam form: Used in thermal insulation, heating, and cooling sectors
• Footwear sector: Used extensively in soles and insoles
• Construction: Used in insulation, coating, adhesives, and sealants
• Automotive: Used in various car parts and components
• Medical and Healthcare Products: Used in medical equipment production
• Packaging Technology: Used in packaging sensitive or fragile items
• Marine Industry: Used for thermal and sound insulation in boats and ships
• Defense Industry: Used in impact cushions, tactical helmets, and combat boot soles
• Aircraft Industry: Used in airplane seats and cabin components

Chemical and Physical Properties

• High mechanical strength and durability
• Excellent chemical resistance
• Versatile formulation possibilities
• Low density and lightweight characteristics
• Superior insulation properties
• High abrasion resistance
• Excellent flexibility and elasticity
• Good dimensional stability
• Resistance to environmental factors
• Customizable hardness and flexibility
• High load-bearing capacity
• Good adhesion properties