Polyurethanes in Industrial Production: How to Choose the Right System Based on Mechanical and Chemical Requirements
Choosing a polyurethane system is not just about price – key factors include mechanical properties, chemical resistance, and processability. How to consider hardness, elasticity, resistance to oils or temperatures, and avoid common mistakes?
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Polyurethanes (PUR) are among the most versatile polymers in industry, but their wide range of properties can also present a challenge. While soft foams for mattresses require high elasticity and breathability, rigid PUR systems for insulation must withstand pressure and temperature fluctuations. In the automotive industry, resistance to oils and fuels is emphasized, whereas in packaging technology, low weight and dimensional stability are critical. How do you correctly define the requirements for a PUR system and choose a supplier that guarantees consistent quality and technical support? This article will help you navigate the key parameters and avoid costly mistakes when making your selection.
Basic Classification of Polyurethane Systems by Chemical Structure
Polyurethanes (PUR) are formed by the reaction of polyols with isocyanates in the presence of catalysts and additives. The basic classification of systems is based on the type of polyol and isocyanate used, which determines their mechanical and chemical properties. Polyester-based polyols provide PUR with higher strength, resistance to oils and solvents, but lower hydrolytic stability. In contrast, polyether polyols ensure flexibility, resistance to water and low temperatures, but with poorer resistance to chemicals. Among isocyanates, MDI (diphenylmethane diisocyanate) and TDI (toluene diisocyanate) dominate – MDI systems are suitable for hard and durable applications, while TDI is more commonly used for flexible foams and elastomers.
The choice between aromatic (MDI, TDI) and aliphatic isocyanates (e.g., HDI, IPDI) primarily affects resistance to UV radiation and color stability. Aromatic systems yellow and degrade in sunlight, whereas aliphatic systems retain transparency and mechanical properties even after long-term exposure to weathering. For industrial applications, it is crucial to consider not only the required properties but also processing parameters such as viscosity, pot life, and reaction temperature.
Mechanical Requirements: How to Choose PUR Based on Strength, Flexibility, and Durability
The mechanical properties of polyurethanes range from soft foams (hardness Shore A 10–30) to rigid composites (Shore D 80 and above). For applications requiring high tensile strength and abrasion resistance, such as conveyor belts or rollers, systems with a high content of rigid segments (e.g., MDI with short polyester polyols) are chosen. Conversely, for damping elements or seals, flexible PUR with a low modulus of elasticity and high elongation (up to 600%) is more suitable.
Another important parameter is resistance to dynamic loading. PUR systems with a higher polyether content better absorb energy and resist material fatigue, which is crucial for applications such as bumpers or flexible joints. For extreme conditions (e.g., high temperatures or aggressive environments), special additives such as antioxidants or UV stabilizers can be used to extend the product's lifespan. It is always necessary to test samples under real-world conditions, as laboratory results may not fully correspond to operational stresses.
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Chemical resistance: When to choose polyester and when polyether systems
The chemical resistance of PUR depends primarily on the type of polyol. Polyester systems excel in resistance to oils, fats, solvents (e.g., acetone, toluene), and many industrial chemicals. They are therefore ideal for applications in the petrochemical industry, mechanical engineering, or the production of seals for hydraulic systems. In contrast, polyether PURs are more sensitive to organic solvents but offer better resistance to water, acids, and alkalis, making them suitable for use in the food industry, medical applications, or outdoor environments.
For extreme chemical environments (e.g., strong acids or oxidizing agents), PUR with a modified structure, such as fluorinated polyols or special additives to enhance resistance, can be used. It is also important to consider the temperature range—polyester systems lose their mechanical properties at temperatures above 100 °C, while some polyether variants can withstand short-term exposure up to 130 °C. When selecting a system, it is essential to verify compatibility with specific chemicals using standard test methods, such as swelling tests or assessments of changes in mechanical properties after exposure.
How to Choose a PUR Systems Supplier: Certifications, Technical Support, and Flexibility
When selecting a supplier of polyurethane systems, it is crucial to verify their ability to provide technical support and flexibility in deliveries. A quality supplier should have certified systems in accordance with REACH and CLP, ensuring safety and compliance with European legislation. It is also important whether they offer the possibility to customize formulations to meet specific customer requirements—for example, adjusting hardness, processing time, or adding functional additives (e.g., flame retardants, antistatic agents).
Technical support should include not only advice on system selection but also assistance in resolving production issues such as insufficient curing, bubbles in the structure, or inadequate adhesion to the substrate. The supplier should be able to provide samples for testing and supply detailed technical data sheets with information on mechanical, chemical, and processing properties. For long-term cooperation, it is advantageous to choose a partner with a broad product portfolio that can cover various applications and thus minimize the need for multiple suppliers.
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Temperature stability and resistance of polyurethanes: A key factor for extreme conditions
Polyurethanes in industrial applications often encounter temperature fluctuations, whether high operating temperatures in mechanical engineering or low temperatures in cooling systems. Selecting the right PUR system must therefore consider its temperature stability. Polyether polyurethanes generally exhibit better resistance to low temperatures (down to -40 °C) due to the flexible structure of polyether chains, which prevents material embrittlement. Conversely, polyester systems tolerate higher temperatures (up to 120 °C) better thanks to stronger ester bonds that resist thermal degradation.
For applications with cyclic temperature loads, such as seals in engines or insulation elements in energy sectors, hybrid systems combining the advantages of both types are suitable. It is also important to consider the processing temperature – some PUR systems require preheating components to 40–60 °C to achieve optimal viscosity and mixture homogeneity. When selecting a supplier, ask about certified temperature resistance tests, which should include standard method tests, such as long-term exposure to elevated temperatures followed by measurement of mechanical properties.
The Impact of Additives on Polyurethane Properties: How to Optimise Performance for Specific Applications
Basic PUR systems can be significantly enhanced with additives that tailor their properties to specific requirements. To increase abrasion resistance, fillers such as microspheres or glass fibres are used to reinforce the material structure. For applications requiring reduced flammability, flame retardants, such as those based on phosphorus or halogens, are key, though they must be selected with regard to ecological regulations (e.g., REACH).
Another group of additives are plasticizers, which increase the flexibility of PUR systems for applications such as sealants or flexible coatings. To improve adhesion to substrates, silane or titanate coupling agents are added. When selecting a supplier, it is important to verify whether they offer the possibility of customizing PUR systems with additives – ideally with technical support that helps choose the right combination for a given application. Also, do not forget about the compatibility of additives with other system components to avoid undesirable reactions or deterioration of mechanical properties.
Ecological and Safety Aspects of Working with PUR Systems: What You Need to Know
Working with polyurethanes is subject to strict safety and environmental regulations that must be followed from the raw material selection stage. According to the REACH regulation, all components of PUR systems must be registered and classified under CLP/GHS, which includes hazard labeling and safety data sheets. Isocyanates, a key component of PUR, are classified as respiratory sensitizers and require special protective measures during handling, such as extraction systems or respirators.
The ecological aspect concerns not only safety during processing but also the durability and recyclability of the final product. Polyether PUR systems are generally more biologically resistant and less prone to hydrolysis, which extends their lifespan in demanding conditions. For applications requiring a reduced environmental impact, PUR systems based on renewable raw materials, such as polyols from vegetable oils, are available. When selecting a supplier, ask about the availability of certifications such as ISO 14001 or EPD (Environmental Product Declaration), which confirm compliance with environmental standards throughout the entire production chain.
Need help choosing a polyurethane system?
Every PUR system requires an individual approach – from raw material selection to processing optimization. GCG Group provides detailed technical data sheets, safety data sheets (SDS), and consulting for specific applications with the supplied polyols and isocyanates. Contact us with your requirements and get a tailor-made solution. Get in touch – or browse our catalog of over 1,300 products right away.
