Detailed introduction of polyurethane sealing materials

Polyurethane (PU for short) is a polymer material. Due to its excellent elasticity, wear resistance, toughness and wide applicability, it is widely used in seals, especially sealing strips, sealing rings and other industrial and daily necessities. This article will give a detailed introduction to the composition, characteristics, classification, production process, application fields and advantages of polyurethane.

1. Composition of polyurethane

Polyurethane is a polymer generated by chemical reaction of isocyanate (such as diisocyanate) and polyol. In the actual production process, various additives such as catalysts, chain extenders, fillers, antioxidants, flame retardants, etc. are often added according to different performance requirements to optimize the mechanical properties, heat resistance, chemical corrosion resistance, etc. of the material.

Isocyanate: mainly provides the hard segment of polyurethane material, affecting the rigidity and heat resistance of the material.

Polyol: mainly provides the soft segment of polyurethane material, affecting the elasticity and flexibility of the material.

Additives: according to different needs, different additives are added to improve the specific properties of the material, such as UV resistance, aging resistance, flame retardancy, etc.

2. Characteristics of polyurethane sealing materials

The reason why polyurethane sealing materials are widely used in various seals is mainly due to their unique material properties:

High wear resistance: The wear resistance of polyurethane is several times that of rubber, and even in some extreme working conditions, its wear resistance exceeds that of metal materials.

Good elasticity: Polyurethane materials have excellent elasticity and can quickly recover to their original state after being subjected to external forces to maintain sealing performance.

High strength and toughness: Polyurethane materials have high tear strength and impact resistance, and are suitable for high load and frequent movement occasions.

Oil resistance and chemical corrosion resistance: Polyurethane has good tolerance to oil, aliphatic hydrocarbons, salt water, etc., and is not easily corroded or swollen.

Adjustable hardness: By adjusting the ratio of isocyanate and polyol, polyurethane materials of different hardness can be produced to meet different application requirements.

Low temperature resistance: Polyurethane materials can still maintain good elasticity and flexibility in low temperature environments and are not easy to become brittle.

Good anti-aging performance: In ultraviolet rays, ozone and other environments, polyurethane materials have good anti-aging performance.

3. Classification of polyurethane sealing materials

Polyurethane materials can be divided into the following categories according to their different characteristics and application occasions:

Thermoplastic polyurethane (TPU):

Features: It has good elasticity and toughness and can be processed multiple times by heating. Suitable for occasions requiring high elasticity and wear resistance.

Application: Used to manufacture sealing strips, sealing rings, hoses, etc.

Casting polyurethane (CPU):

Features: It has excellent mechanical properties and high wear resistance. It is produced by casting molding process and is suitable for seals of large size and complex shape.

Application: Used to manufacture industrial equipment seals, heavy machinery seals, large hydraulic cylinder seals, etc.

Thermosetting polyurethane (TSU):

Features: It has excellent heat resistance and chemical corrosion resistance. It is cured and molded by chemical reaction. It cannot be heated and melted again after molding.

Application: Used to manufacture seals under high temperature and high pressure environment.

Foamed polyurethane:

Features: It has a porous structure and has excellent sound absorption, heat insulation and buffering properties.

Application: Used to manufacture cushions, heat insulation sealing strips, etc.

4. Production process of polyurethane sealing materials

The production process of polyurethane sealing materials mainly includes the following steps:

Raw material preparation: According to the product performance requirements, select appropriate isocyanate, polyol and additives, and mix and proportion them.

Reaction synthesis: Chemically react isocyanate and polyol to generate polyurethane prepolymer.

Molding process: According to the different forms and requirements of the product, different molding processes are adopted, such as casting molding, injection molding, extrusion molding, etc.

Post-processing:

Curing: According to the type of polyurethane, complete the necessary curing treatment. For thermosetting polyurethane, it can be cured under certain temperature and time conditions to achieve the required hardness and performance.

Surface treatment: Surface treatment of the cured polyurethane material, such as polishing, coating or spraying, to improve its surface performance and appearance quality.

Inspection: Carry out product performance testing and quality control, such as tensile strength, hardness, wear resistance, compression strength, etc., to ensure that the product meets the technical standards.

5. Application fields of polyurethane sealing materials

Polyurethane sealing materials are widely used in many fields, mainly including:

Automotive industry:

Used in sealing parts of automobile generators, transmissions, suspension systems and window seals, providing effective water and dust resistance.

Construction engineering:

Applied to the sealing of windows, thresholds and walls to prevent water and air leakage and improve energy saving.

Industrial equipment:

Widely used in seals of pumps, compressors, hydraulic cylinders, pneumatic equipment, etc. to ensure the normal operation of equipment and reduce the risk of leakage.

Household appliances:

Used in the sealing of washing machines, refrigerators, air conditioners and other equipment to prevent energy loss and moisture penetration.

Medical and food industry:

In food processing machinery and pharmaceutical equipment, polyurethane seals are widely used due to their good cleaning and corrosion resistance.

Electronic products:

Applied to the sealing of electronic components and sensors to protect internal circuits from moisture and other environmental factors.

6. Advantages of polyurethane sealing materials

Superior performance:

The high wear resistance, high elasticity and good chemical corrosion resistance of polyurethane sealing materials make them perform well under a variety of harsh working conditions.

Long service life:

Due to the anti-aging and UV resistance of polyurethane materials, their service life is generally longer than that of traditional rubber seals.

Strong environmental adaptability:

Polyurethane materials can maintain stable performance in low and high temperature environments, are not prone to brittleness or aging, and are ideal for high temperature, high pressure and extreme environments.

Processing flexibility:

Polyurethane materials can be manufactured into seals of various shapes and sizes through different processes (such as casting, injection molding, extrusion) to meet diverse application needs.

Green and environmental protection:

Modern polyurethane materials can achieve low VOC (volatile organic compound) design to a certain extent, which is environmentally friendly and meets the environmental protection requirements of today's society.

VII. Summary

Polyurethane sealing materials have become an indispensable sealing material in modern industry and daily life with their excellent performance, wide range of application fields and excellent environmental adaptability. With the development of technology, the performance of polyurethane materials will continue to improve, providing more reliable and durable solutions for all walks of life. When selecting polyurethane sealing materials, their use, environment and performance requirements should be comprehensively considered to achieve the best application effect.

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