Polyurethane Foam: Application, Production, Types and Composition

Polyurethane is a polymer composed of organic joints of carbamate (urethane). Polyurethane is generally produced from a wide range of materials known as monomers and thus it is known as a class of polymers. The physical properties are very different which leads to a wide variety and different applications. They are basically rigid and flexible foams. Foams are the largest single application comprising 67% of all polyurethane produced according to the study conducted in 2016.

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Compositions of Polyurethane Foam 

The first type of flexible polyurethane foam was developed in the early 1950s which was known as polyether foam which offers a wide range of properties. The formula of polyurethane foam is C₂₇H₃₆N₂O₁₀. The structure is as follows:

• PU foams are the reaction between an isocyanate prepolymer and polyol with an amine which acts as a catalyst acting as a blowing agent.
• Blowing agent is carbon dioxide which is formed as a byproduct of the reaction between water and isocyanate.
• PU Foams are mainly formed from polyol which are generally polyethylene oxide, or polyester based polyol.

The video below explains this:

Polyurethane Foam Detailed Video Explanation:

Read about: High Density Polyethylene

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Production of Polyurethane Foam

Polyurethanes are produced by mixing two or more liquid streams. The polymer stream contains catalysts, surfactants, and blowing agents. These components are referred to as polyurethane systems. The isocyanate is also known as ‘A side’ and the blend of polyols is referred to as ‘B side’. The mixture is called ‘resin’. Resin is used for blending additives which includes chain extenders, cross linkers, surfactants, blowing agents, pigments. Polyurethane is multipurpose and it can be made in a variety of densities and the hardness can vary due to different elements such as isocyanate, polyol or additives.

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Types of Polyurethane Foam

• Flexible Polyurethane Foam

Flexible polyurethane foam is light in weight, durable. They are used in everyday life today. PUR foams are categorized depending on their chemical structure and according to their production method. They are supportive and make it comfortable. The major use of this type of foam is in cushioning, making mattresses, furniture, interiors of automobiles and packaging.

• Rigid Polyurethane Foam 

They are the most economical and energy efficient and for saving energy. They are mostly used in roof and wall insulation, for insulating windows and doors. They help in maintaining temperature and for soundproofing the room. They are also used as an thermal insulator in refrigerators and freezers.

• Adhesives

They can enhance the appearance of the product and help in increasing the lifespan of the product. They help in increasing the shine to the surface of an object. They help in increasing the durability.

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Physical Properties of Polyurethane Foam 

• Resilience 

Resiliency leads to cushioning applications, particularly bedding. Between polyester and polyether foams , the difference is low resilience of polyester foams. Polyester foams have high tensile strength. Hence they are used in polishing foam applications. The lower resiliency and high energy absorbency makes them suitable for use in packaging applications.

• Solvent Resistance

Polyurethane foams are resistant to a wide variety of solvents. Polyester foams are superior especially in their resistance properties. Applications of this are mostly in manufacturing foams for textile laminates. Polyurethane foams degrade by aqueous acids, alkalis and steam. Polyether foams are generally more resistant to hydrolysis than polyester foams.

• Antibacterial Protection

Polyurethane foams have antibacterial and antifungal properties. They are also used in medicine. Several antimicrobial additives are available which can be introduced into the PU foam at the manufacturing.

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Chemical Properties of Polyurethane Foam

On the oxidation, polyurethane foam forms hydrazoic acid, carbon dioxide and water. The chemical reaction is as follows:

6C₂₇H₃₆N₂O₁₀ +185O₂ →162CO₂ + 106H₂O + 4HN₃

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Application of Polyurethane Foam 

1. Appliances 

Polyurethanes is a major component and is used in everyday life. It is used in major appliances such as refrigerators and freezer thermal insulation systems. The type of foam used is rigid as they are cost effective that can be used for meeting required energy ratings.

2. Automobiles 

Polyurethane is used throughout the cars. From making car seats to bumpers to interior to ceiling of the car and doors and windows. It also helps in increasing mileage because they are light in weight, increase in fuel economy, insulation and sound absorption.

3. Construction

Polyurethane is environment friendly and also helps in conserving natural resources. It is used in the house on floors such as carpets. Foam panels offer a wide variety of colors to walls and roofs .

4. Electronics

It is used in electrical and electrical industries to encapsulate, seal and insulate underwater cables and circuit boards. Polyurethane is formed to meet diverse demands of physical, thermal and electrical properties.

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Points to Remember 

• Polyurethane foam is a porous, cellular structured synthetic material made from the reaction of polyols and diisocyanates.
• There are two main types of foams- flexible polyurethane foam and rigid polyurethane foam.
• The properties and uses of the foam revolves around density and durability of the foam.
• Polyurethane foam contains polyol, diisocyanates, blowing agents, catalysts, surfactants, cross-linkers and extenders.

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