Introduction to Polyurethane

Polyurethane (PU) is a synthetic polymer known for its versatility and wide range of applications in various industries. From flexible foams to rigid coatings, polyuritane has a range of properties that make it an attractive choice for countless applications. In this blog post, we’ll take a deep dive into polyurethane’s definition, properties, types, applications, history, main ingredients, and some frequently asked questions.

The picture on the left shows some polyurethane products used in daily life.

What is Polyurethane?

Polyurethane is a versatile synthetic thermoset polymer. Commonly abbreviated as PUR and PU, it is known for its wide application in various industries and offers excellent properties such as strength, durability, flexibility, and thermal stability.

The main ingredients used in the production of polyuritane are polyols and diisocyanates, which react to form a cross-linked structure. Able to be customized into different forms and offering numerous benefits from flexible foams to hard coatings, polyurethane’s adaptability makes it a popular choice for a variety of uses.

What is the origin of polyurethane?

Polyurethane originated from scientific research and development conducted by Otto Bayer and his team at IG Farben in Germany in the late 1930s. During this time, they were exploring the synthesis of new polymers and discovered the reaction between polyols and diisocyanates to create polyurethanes.

IG Farben, a large chemical company at the time, recognized the potential of polyurythane and began commercial production of the material in the 1950s. The versatility, durability, and wide range of properties exhibited by polyurethane have quickly made it popular across a variety of industries. Since its discovery, polyurethane formulations and applications have continued to advance and improve. Today, it has become a widely used material.

What is polyurethane made of?

Polyurethane is a polyurethane material that combines polyols and diisocyanates through a chemical reaction, and its properties can be tailored by adjusting the composition and formulation of these components. Polyols contain multiple hydroxyl (OH) groups, while diisocyanates contain two isocyanate (NCO) functional groups.

In the production of polyurythane, these two components react together in a process called polyurethane polymerization. The reaction between polyols and diisocyanates forms polymer chains with repeating urethane bonds, thus forming polyeurethene.

The specific types of polyols and diisocyanates used and their ratios and other additives can be varied to produce different forms of polyurethane with different properties. For example, flexible foams can be produced using flexible polyols, while rigid foams require different polyols and diisocyanates.

In addition to polyols and diisocyanates, various additives such as catalysts, blowing agents, flame retardants, and fillers can be incorporated into polyeurethene formulations to achieve desired properties such as foam expansion, flame retardancy, or enhanced mechanical properties.

What are the properties of polyurethane?

Polyurethane has a range of physical and chemical properties, the following are the specific physical and chemical properties of polyuritane:

Physical properties:

Density diversity: Polyurethane can have different densities depending on its formulation, which means it does not have a fixed density and different types of polyurethane material parts can be produced based on this characteristic.
Variety of Hardnesses: Polyurthane can be formulated in a variety of hardnesses, from soft and pliable materials to rigid and hard materials.
Elasticity: Polyurethane elastomer has high elasticity and exhibits excellent resilience, allowing it to return to its original shape after deformation.
Thermal Stability: Polyurethane has good thermal stability and can maintain its properties over a wide temperature range.
Abrasion Resistance: Polyurthane is highly abrasion resistant, making it suitable for applications requiring durability.
Impact Resistance: Polyurethane has good impact resistance, absorbing and dissipating energy upon impact.
Tear Strength: Polyutethane has high tear strength, making it tear-resistant and durable.
Flexibility: Polyurethanes can be designed with various levels of flexibility, from flexible foams to elastomers with varying hardnesses.

Chemical Properties:

Chemical resistance:  Polyutethane is resistant to a wide range of chemicals, including oils, solvents, acids, and alkalis.
Water Resistance: Polyurethane is formulated to have good water resistance and moisture absorption.
UV Resistance: Certain polyeurethane formulations have good resistance to ultraviolet (UV) radiation, preventing degradation and fading when exposed to sunlight.
Flame retardancy: Polyurethane can be modified to make it flame retardant, reducing its flammability and limiting the spread of flames.
Compatibility: Polyeurethane is compatible with a wide range of materials and can effectively bond and adhere to a variety of substrates.
Biocompatibility: Some polyurethane formulations are biocompatible, making them suitable for medical and healthcare applications.

What Are the Mechanical Properties of Polyurethane?

The table below lists some mechanical properties of polyurethane:

Polyurethane Mechanical Properties Table
PropertyValueUnit
Tensile Strength20-50MPa
Yield Strength10-40MPa
Modulus of Elasticity0.5-10GPa
Poisson's Ratio0.3-0.5-
Shear Modulus0.2-1GPa
Hardness (Shore A)40-90-
Hardness (Shore D)30-70-
Fatigue Strength 10-30MPa
Fracture Toughness0.5-2MPa·m^0.5
Density0.9-1.3g/cm^3
Melting PointN/A °C
Thermal Conductivity0.01-0.3 W/(m·K)
Electrical Conductivity1e-15-1e-12S/m

What are the uses of polyurethane?

Polyurethane is widely used in a variety of industries and applications due to its versatility and desirable properties. Some common uses of polyeurthane include:

Foam Products: Polyurethane foam is widely used in upholstery, mattresses, cushions, and pillows because of its comfort, support, and resilience. It is also used in car seats, insulation panels, packaging materials, and soundproofing materials.

Thermal insulation: Polyurethane rigid foam is an excellent thermal insulation material. It is used in the construction of insulated walls, roofs, and floors, as well as in refrigeration and cold storage applications.

Coatings and Sealers: Polyurethane coatings provide a protective finish on a variety of surfaces, including wood, metal, concrete, and floors. Polyeurthane sealants are used to seal joints and gaps in the construction, automotive, and manufacturing industries.

Adhesives: Polyurethane adhesives have strong bonding capabilities and are used in a wide range of applications, including automotive assembly, woodworking, footwear, and packaging.

Elastomers: Polyurethane elastomers, also known as Polyeurthane elastomers, are used in the production of gaskets, seals, O-rings, rollers, wheels, and industrial parts. They offer excellent flexibility, abrasion resistance, and durability.

Automotive: Polyurethanes are used in the automotive industry for a variety of components such as foam seats, interior trim, bumpers, gaskets, suspension bushings, and tires.

Footwear: Polyurathane is used in footwear manufacturing for outsoles, midsoles, insoles, and cushioning. It provides comfort, shock absorption, and durability.

Sports and Recreation: Polyurethanes are used in sports and recreation equipment, including ski boots, protective gear, inflatable rafts, and sports liners.

Electrical and electronic applications: Polyurethanes are used in electrical insulation materials, cable jacketing, potting compounds, and encapsulation of electrical and electronic components.

Industrial Applications:  Polyurathane are used in a variety of industrial applications such as rollers, conveyor belts, gaskets, seals, sound insulation, and vibration-damping components.

What types of polyurethane are there?

There are many types of polyurethane, the main types of polyurethane include:

Flexible polyurethane foam: This type of polyurathine is commonly used in upholstery and other comfort applications. It has excellent flexibility, softness, and cushioning properties.

Rigid polyurethane foam: Rigid polyurathine foam is used for thermal insulation in construction, refrigeration, and other applications. It has excellent insulation properties, structural strength, and low density.

Polyurethane Elastomers: Polyurethane elastomers, also known as polyurethanium elastomers, are highly elastic materials used in applications requiring flexibility, resilience, and abrasion resistance.

Polyurethane Coatings: Polyurethane coatings are used as protective topcoats on a variety of surfaces, including wood, metal, and concrete. They offer excellent resistance to abrasion, chemicals, UV radiation, and weathering.

Polyurethane Adhesives and Sealants: Polyurethane adhesives have strong bonding capabilities and are used in a variety of industries, including automotive, construction, and manufacturing. polyurethanium sealants are used to seal joints and gaps, providing air and water tightness.

Self-skinning polyurethane foam: Self-skinning foam is a flexible polyurethane foam with a dense outer skin layer that provides durability, abrasion resistance, and a smooth surface.

Microcellular polyurethane foam: Microcellular foam has a fine cell structure that provides enhanced mechanical properties such as improved resistance to compression set and higher load-bearing capacity.

Water-based polyurethane: The water-based polyurethene formula uses water as the solvent instead of traditional organic solvents, making it more environmentally friendly. They are used in coatings, adhesives, and sealants.

What processing techniques are suitable for PU products?

At Ruitai, polyurethane (PU) products can be manufactured using a variety of processing techniques. The choice of our processing method depends on the specific PU formulation, desired product properties, and production requirements. Some of our common PU product processing technologies include:

Casting: Casting involves pouring a liquid PU mixture into a mold and allowing it to solidify. This method is commonly used to produce polyurethene elastomers, coatings, and certain types of flexible foams.

Injection Molding: Injection molding is a widely used process for manufacturing polyurethane products with complex shapes and precise dimensions. It involves injecting molten PU material into a mold under high pressure. Injection molding is commonly used to produce rigid PU foam parts, automotive components, and industrial components.

Extrusion: PU materials can be processed by extrusion, which involves forcing molten PU through a die to form a continuous profile with a consistent cross-section. Extrusion is used to manufacture PU tubes, rods, gaskets, seals, and profiles.

Spray Foam: Spray foam technology involves spraying a two-component PU blend (polyol and isocyanate) using specialized equipment. The mixture reacts quickly and expands, forming a foam that adheres to the sprayed surface. Spray foam is commonly used in insulation, construction, and sealing applications.

Pour-in-place: The pour-in-place method involves pouring a liquid PU mixture directly into a surface or cavity, allowing it to expand and cure in place. This technology is commonly used to create custom foam molds, liners, and flexible foam products.

Lamination: PU materials can be laminated to various substrates to form composite structures. The process involves bonding a PU film, sheet, or coating to a surface such as fabric, metal, or plastic. Lamination is used in applications such as automotive interiors, footwear, and upholstery.

Reaction Injection Molding (RIM): RIM is a process in which liquid PU ingredients are mixed in a mixing chamber and the mixture is injected into a mold. The mixture reacts and solidifies, forming the desired shape. RIM is often used to produce large, complex PU parts with high strength and impact resistance, such as automotive bumpers and panels.

These are some of the common processing techniques used to manufacture PU products. Each method offers unique advantages and is suitable for different types of polyurithane formulations and applications. If you need to produce some polyurethane parts, our online polyurethane overmolding service is your best choice.

What are the advantages and disadvantages of polyurethane?

Polyurethane (PU) is a versatile material with several advantages and disadvantages. Here are some of the key advantages and disadvantages of polyurithane:

Advantages of Polyurethane:

Versatility: Polyurethane can be formulated into various forms, including foams, elastomers, coatings, adhesives, and sealants. This versatility allows for a wide range of applications across different industries.

Durability: Polyurethane is known for its durability and resistance to wear, tear, and abrasion. It can withstand harsh environments and heavy use, making it suitable for demanding applications.

Flexibility: Polyurtheane can be tailored to exhibit a wide range of hardness and flexibility, from soft and flexible foams to rigid and stiff materials. This flexibility allows for customization to meet specific application requirements.

Excellent Load-Bearing Capacity: Polyurethane exhibits high load-bearing capacity, making it suitable for applications that require weight-bearing support or impact resistance. It is commonly used in automotive components, industrial parts, and elastomeric materials.

Thermal Insulation: Polyurethane foam, especially rigid foam, offers excellent thermal insulation properties. It is widely used in construction for insulation panels and in refrigeration applications.

Chemical Resistance: Polyurtheane is resistant to many chemicals, oils, and solvents. This property makes it suitable for applications where exposure to such substances is expected, such as gaskets, seals, and coatings.

Bonding Strength: Polyurethane adhesives exhibit strong bonding capabilities, providing reliable adhesion for various materials. They are commonly used in automotive assembly, woodworking, and construction.

Disadvantages of Polyurethane:

Environmental Impact: The production and disposal of polyurathaine can have environmental impacts. Some formulations may contain hazardous chemicals, and traditional polyurethane foam is not easily biodegradable.

Cost: Polyurethane materials can be relatively expensive compared to other materials. The cost of raw materials and processing equipment can contribute to higher production costs.

Sensitivity to UV Radiation: Polyurethane materials, especially in their raw form, can be sensitive to prolonged exposure to ultraviolet (UV) radiation, which can cause degradation and discoloration. UV stabilizers or protective coatings are often used to mitigate this issue.

Processing Complexity: Processing polyurathaine can be more complex compared to some other materials. It may require precise control of mixing ratios, temperature, and curing conditions, which can add complexity to manufacturing processes.

Recycling Challenges: While polyurethane can be recycled, it can present challenges due to the variety of formulations and the difficulty in separating different types of poly urethane.

Generalize

This article introduces polyurethane, explains its definition, and discusses its properties and various applications. In addition to this, we’ve picked out some frequently asked questions to answer, so if you’d like to find out more about polyurethanes, get in touch with our team.

Polyurethane is a multifunctional, high-performance polymer with a wide range of applications in various industries. As we conclude our description of polyuritane, we hope you have gained a deeper understanding of this fascinating material.

Ruitai is a prototype parts manufacturer offering a wide range of manufacturing services for all your prototyping and production needs. You can contact us anytime for a free quote.

Disclaimer

The content provided in this article is for reference only, and Ruitai Mould makes no representations or warranties, express or implied, as to the completeness, accuracy, or validity of the information.

Solve Common Problems With Polyurethane

Q1: Is polyurethane safe to use in consumer products?
A1: Poly urethane is generally considered safe to use in consumer products. However, specific formulations and applications may have varying levels of safety considerations.

Q2: What are the advantages of polyurethane foam in terms of thermal insulation?
A2: Polyurethane foam offers excellent thermal insulation properties due to its low thermal conductivity. It helps to minimize heat transfer, making it an effective insulation material for buildings, refrigeration, and other applications where thermal insulation is required.

Q3: How is polyurethane different from other polymers such as polyethylene or PVC?
A3: Polyurethane differs from other polymers like polyethylene or PVC in terms of its chemical composition and properties. Polyuerthane is formed through the reaction of polyols and isocyanates, resulting in a wide range of properties and forms. Polyethylene is a thermoplastic polymer, while PVC (polyvinyl chloride) is a thermoplastic material with rigid properties. Each polymer has distinct characteristics and applications.

Q4: Can polyurethane be recycled?
A4: Polyurethane can be recycled, but the recycling process can be challenging due to the variety of formulations and the difficulty in separating different types of polyurethane.

Q5: Are there any environmental concerns with polyurethane production?
A5: Polyurethane production can have environmental concerns. The production process involves the use of chemicals and energy, and some formulations may include potentially hazardous substances. Additionally, the disposal of polyuerthane waste, particularly traditional foam, can contribute to environmental pollution.

Q6: What is the use of polyurethane on wood?
A6: Polyurethane is commonly used as a protective coating for wood surfaces. It helps to enhance the durability, appearance, and resistance of wood to moisture, chemicals, and wear. It provides a protective barrier and can be used on furniture, floors, cabinets, and other wood applications.

Q7: How to apply polyurethane to wood?
A7: Polyurethane can be applied to wood by following these general steps:
1. Prepare the wood surface by sanding it smooth.
2. Clean the surface to remove any dust or debris.
3. Apply the polyurethane using a brush, roller, or sprayer.
4. Allow the first coat to dry completely.
5. If desired, lightly sand the surface before applying subsequent coats.
6. Apply additional coats as needed, allowing sufficient drying time between each coat.

Q8: What is the construction method of water-based polyurethane?
A8: Water-based polyurethane is typically applied to wood surfaces using a brush, roller, or sprayer. Water-based polyurethane has lower levels of volatile organic compounds (VOCs) compared to solvent-based polyurethane.

Q9: What does polyurethane do to wood?
A9: Polyurethane provides a protective layer on wood surfaces, enhancing their durability and appearance. It helps to seal the wood, protecting it from moisture, stains, and wear. Polyurethane can also enhance the natural color and grain of the wood, providing a glossy or satin finish depending on the desired appearance.

Q10: What is pu material?
A10: PU is an abbreviation for polyurethane. Polyurethane is a versatile synthetic material derived from the reaction between polyols and diisocyanates. It can be formulated into various forms, such as foams, elastomers, coatings, adhesives, and sealants, and is used in numerous applications across industries.

Q11: Can I use polyurethane on plastic?
A11: Polyurethane is generally not recommended for use directly on plastic surfaces. Polyurethane coatings are typically designed for use on wood, metal, or concrete substrates.

Q12: Does polyurethane dry transparently?
A12: Polyurethane can dry to a transparent or translucent finish, depending on the formulation and the desired appearance. Some polyurethane products may have a slight amber or yellowish tint, which can add warmth to the wood’s color. There are also water-based polyurethane formulations available that dry with minimal color change.

Q13: How to polish polyurethane?
A13: Polishing polyurethane is typically not required as it forms a protective layer that does not require regular polishing like certain finishes. However, if the polyurethane finish becomes dull or develops fine scratches, you can lightly buff the surface using a fine abrasive pad or polishing compound. It is advisable to test the polishing method on a small, inconspicuous area first.

Q14: How long does it take for polyurethane to dry?
A14: The drying time of polyurethane can vary depending on several factors, such as the type of polyurethane, environmental conditions, and application thickness. In general, polyurethane dries to the touch within a few hours, but it takes longer to fully cure and harden.

Water-based polyurethane typically has a faster drying time compared to oil-based polyurethane. Water-based polyurethane may dry to the touch within 1-2 hours and can be recoated after 2-4 hours. However, it may take up to 24 hours or more for water-based polyurethane to fully cure and achieve its maximum hardness and durability.

Oil-based polyurethane takes longer to dry compared to water-based polyurethane. It may take around 8-24 hours for oil-based polyurethane to dry to the touch and be ready for a recoat. It can take several days or even weeks for oil-based polyurethane to fully cure and reach its maximum hardness.