Polyurethane is found in many products we use in our daily lives without even realizing it. From automobile seats to mattresses, refrigerator and cold room insulation to shoe soles, and construction chemicals to floor coatings, polyurethane appears in many different sectors.
So, what is polyurethane, and what are the properties that make this material usable in such a wide range of applications?
Polyurethane is essentially a polymer family formed as a result of the chemical reaction of raw materials containing polyol and isocyanate groups.
The polyurethane formed as a result of this reaction can exhibit completely different properties depending on the structure of the polyol used, the type of isocyanate, additives, catalysts, and formulation ratios.
One of the most important properties of polyurethane is that products with completely different physical properties can be obtained when the formulation is modified.
In other words, polyurethane can be considered a broad family of materials rather than a single material.
Polyurethane systems can be developed depending on the formulation, the structure of the polyol and isocyanate used, additives, catalysts, and process conditions.
• Rigid or flexible,
• Lightweight or dense,
• Elastic or rigid,
• Soft or high hardness,
• Open or closed-cell,
• Water and chemical resistant,
• Abrasion resistant,
• Providing thermal insulation
How is Polyurethane Produced?
At the core of polyurethane systems lies the reaction between polyol and isocyanate.
While the polyol side contains hydroxyl (OH) groups, the isocyanate side contains reactive NCO groups. When these two components come together in appropriate ratios, the reaction occurs and the polyurethane structure is formed. However, in practice, the process does not consist solely of mixing two raw materials together.
Depending on the target properties of the product, various additives can be added to the system, such as:
• Catalysts,
• Silicone surfactants,
• Chain extenders,
• Crosslinkers,
• Flame retardants,
• Fillers,
• Pigments,
• Plasticizers,
• Stabilizers
can be added.
Therefore, products with significantly different properties can be found under the same “polyurethane” definition.
What are the Types of Polyurethane?
One of the most important advantages of polyurethane technology is that it can be specially designed for different applications.
Polyurethane Rigid/Flexible Foams
Polyurethane foams are widely used, especially in thermal and acoustic insulation applications.
Rigid polyurethane foams are preferred in buildings, cold room panels, refrigerators, and various industrial insulation applications due to their low thermal conductivity.
Flexible polyurethane foams, on the other hand, are mostly used in areas such as furniture, mattresses, seating, automotive seats, and sponge applications.
Polyurethane Elastomers
Polyurethane elastomers stand out in applications where elasticity and mechanical strength are required together.
They can be used in technical parts where abrasion, impact, and tear resistance are important.
Wheels, rollers, vibration dampers, gaskets, and various elastomeric parts are some of the application areas for polyurethane elastomers.
Polyurethane Coatings
Polyurethane coatings are used to protect surfaces against environmental and mechanical effects.
Depending on the application, properties such as:
• High abrasion resistance,
• Flexibility,
• Water resistance,
• Chemical resistance,
• UV resistance,
• High adhesion
can be expected from the coating.
Therefore, polyurethane coatings can be used in construction, automotive, machinery, flooring, and industrial applications.
Polyurethane Adhesives
Polyurethane-based adhesives are used to ensure a strong bond between different materials.
What are the Advantages of Polyurethane?
The most important feature that distinguishes polyurethane from many other polymer systems is that its properties can be designed within a wide range.
Application-specific polyurethane systems can be developed with the right raw materials and the right formulation.
Its prominent advantages include:
High mechanical strength:
Systems with high tensile, tear, and impact resistance can be obtained with appropriate formulations.
Flexibility:
High elongation and elastic recovery can be achieved, especially in elastomeric polyurethanes.
Abrasion resistance:
The abrasion resistance of polyurethane elastomers is a significant advantage in applications with intense mechanical movement.
Adhesion performance:
Strong adhesion can be achieved on concrete, metal, wood, and various polymeric surfaces with the appropriate recipe and surface preparation.
Chemical resistance:
Depending on the formulation, systems resistant to oil, fuel, solvents, and various chemicals can be designed.
Thermal insulation:
Rigid polyurethane foams, in particular, are among the effective insulation materials due to their low thermal conductivity.
How to Choose the Right Polyurethane System?
When choosing a polyurethane system, making a decision based solely on price or the general name of the product may not yield the correct results.
First, the conditions under which the product will operate must be determined.
For example, questions such as:
• Which surface will the product be applied to?
• Should it be rigid or elastic?
• What should the tensile and tear strength be?
• Will it be constantly exposed to water?
• Will it be exposed to UV or high temperatures?
• Will it come into contact with chemicals?
• What is the application temperature?
• How long should the mixing and curing time be?
• At what thickness will the final product be used?
should be answered.
In line with this information, an application-specific polyurethane system can be designed by determining the appropriate combination of polyol, isocyanate, and additives.