Polyurethanes Under the Microscope: 7 Unexpected Storage and Handling Mistakes That Cost Money
Even minor oversights in the storage or handling of polyurethanes can lead to raw material degradation, loss of properties, or safety risks. How can you prevent the most common mistakes and save time and costs?
Photo: Brayden Prato / Unsplash
Polyurethanes are among the most versatile polymers, but even experienced manufacturers often underestimate their sensitivity to external conditions. Moisture, temperature, improper mixing, or contamination can degrade raw materials worth tens of thousands of crowns within days. Yet, adhering to a few technical principles—from proper sealing of packaging to monitoring component expiration—can prevent this. In this article, we focus on specific mistakes that recur in practice and demonstrate how to avoid them with minimal costs for preventive measures.
1. Underestimating moisture: How water turns polyurethanes into unusable material
Polyurethanes are extremely sensitive to moisture. Even a small amount of water in the isocyanate component or polyol can trigger an undesirable reaction, leading to the formation of carbon dioxide and foaming of the mixture. The result is a material with inferior mechanical properties, bubbles, or even a completely unusable product. Typical symptoms include increased viscosity, cloudiness, or sediment formation at the bottom of the container. The problem is not limited to open packages – even sealed drums can absorb moisture through poorly sealing lids or damaged gaskets.
Prevention starts with storage conditions. The ideal temperature for storing polyols and isocyanates ranges between 15–25 °C, with relative air humidity not exceeding 60 %. Before opening the package, allow the material to acclimatize for at least 24 hours in a space with controlled humidity. Use dry tools and containers during handling – even residual condensate on the walls can cause issues. For long-term storage, hermetically sealed containers with an inert nitrogen cushion, which displaces airborne moisture, are suitable.
2. Temperature Shocks: Why Sudden Temperature Changes Destroy the Reactivity of PUR Systems
Polyurethanes are sensitive to temperature fluctuations, which can disrupt their chemical stability. Rapid heating or cooling causes component separation, viscosity changes, or even crystallization of certain additives. For example, isocyanates begin to solidify at temperatures below 10 °C, while at temperatures above 30 °C, their spontaneous polymerization accelerates. Polyols, in turn, lose fluidity at low temperatures, complicating dosing and mixing.
Proper storage requires gradual temperature adjustment. If the material is stored in a cold environment (e.g., in an unheated warehouse during winter), allow it to acclimate for at least 48 hours in a room with a temperature of 20–25 °C before use. During transport, use thermal boxes or isothermal containers to minimize temperature fluctuations. It is also important to monitor the expiration date – even properly stored polyurethanes lose reactivity after the shelf life has elapsed, which is typically between 6–12 months from the date of manufacture.
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3. Contamination with residues of other chemicals: How even a small amount can ruin an entire batch
Polyurethanes are highly reactive systems that can react even with trace residues of other chemicals. Contamination may occur when using the same tools for different materials, inadequate cleaning of containers, or even storage near aggressive substances. A typical example is residual catalyst from previous production, which accelerates unwanted reactions, or traces of acids that destabilize the isocyanate component. The result is often gelation of the mixture, color change, or loss of adhesive properties.
The foundation of prevention is strict separation of workspaces and tools. Use only containers and mixers designated exclusively for polyurethanes and thoroughly clean them after each use with a suitable solvent (e.g., acetone or special PUR cleaning agents). Store polyurethanes separately from acids, bases, alcohols, and other reactive substances. During handling, ensure that no foreign objects, such as metal shavings or dust, enter the containers, as these may catalyze unwanted reactions.
4. Incorrect Mixing: Why Even a Perfect Component Ratio Can Fail
Even if you maintain the exact ratio of polyol to isocyanate, incorrect mixing can completely ruin the final properties of the polyurethane. A common mistake is insufficient mixing, which leads to local concentrations of one component and thus a non-homogeneous material structure. Conversely, overly intensive mixing can introduce air bubbles, which weaken mechanical strength. Another issue is mixing at the wrong temperature – material that is too cold mixes poorly, while material that is too hot may react prematurely.
To achieve optimal results, use a mechanical stirrer with adjustable speed (ideally 300–600 rpm) and a mixing head suitable for viscous materials. Stir for 2–5 minutes until the mixture is completely homogeneous, but avoid excessive whipping. The mixture temperature should be in the range of 20–25 °C. For two-component systems, always thoroughly mix the polyol component first before adding the isocyanate. After mixing, let the mixture stand briefly to release any air bubbles, and only then apply it.
Photo: Atik sulianami / Unsplash
Want to be sure your PUR systems last as long as possible?
For every supplied raw material, we provide detailed technical and safety data sheets with recommendations for storage and handling. Our experts will be happy to advise you on selecting suitable conditions or solving specific problems in your production. Contact us – or browse our catalog of over 1,300 products right away.
