Exposed polyurethane is widely used in scenarios requiring long-term outdoor exposure or harsh environments due to its excellent weather resistance, mechanical properties, and environmental adaptability. Below are its typical application areas and technical analysis: Roof waterproofing and refurbishment, outdoor water tank, footbridges, balconies, terraces, roof walkways, parking garages, and other outdoor waterproof projects with pedestrian and/or vehicular traffic.
What are the differences between aliphatic polyurethane and aromatic polyurethane?
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The core difference between aliphatic polyurethane and aromatic polyurethane originates from the presence or absence of aromatic groups (such as benzene rings) in their molecular structures. This structural disparity directly leads to significant differences in their properties and application scenarios. The typical raw materials for aliphatic PU are hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), etc. The typical raw materials fo aromatic PU are Toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), etc. Due to the absence of benzene rings, the molecular structure exhibits stronger stability against ultraviolet (UV) light, with excellent weather resistance. It is less prone to photo-oxidative degradation, maintaining color stability and resisting yellowing after long-term exposure to outdoor or light environments.
What factors affect the curing speed of polyurethane?
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Air temperature, humidity, mixing ratio, coating thickness, air circulation, substrate properties, and atmospheric pressure—all of these factors can affect the curing speed.
Can waterborne polyurethane be stored at temperatures below 0 degrees Celsius?
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No. Waterborne coatings use water as a solvent. When stored below 0 degrees Celsius, the water in the formulation freezes, causing physical damage to the coating. Freezing may form ice crystals, which disrupt the emulsion structure of the polyurethane, leading to irreversible separation, thickening, or gelation.
Can polyurethane coating be used for indoor construction
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Yes, the non-solvent polyurethane and water-based polyurethane can be used for indoor waterproofing applications. Non-solvent polyurethane is a high-solids, ultra-low VOC coating, especially suitable for areas with poor ventilation and sensitivity to odors or volatiles.
What are the differences between sag - resistant PU and levelling PU?
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Sag-resistant PU has rheological properties. Rheology is the study of the behavior of materials during "flow" or "deformation" processes. There are several common "rheological behaviors" from the molecular level:
1) Shear thinning,This is the most common type of non - Newtonian behavior. It means that when you apply a shear force to the material (such as stirring, scraping, extruding), the viscosity of the material will decrease. ;
2) Thixotropy: Thixotropy is an "upgraded version" of shear thinning, with an additional dimension:
time. Its definition is: During the continuous shearing process, the viscosity of the material will gradually decrease with time; after stopping shearing, it can gradually recover the original viscosity. This ability of "temporarily becoming thin + reversibly recovering" is exactly thixotropy. Materials with good thixotropy can "flow smoothly" during construction, but can quickly recover viscosity to avoid "collapse" and "sagging". For the sag-resistant coating, it is easy to scrape and apply during construction, and does not sag when left standing, ensuring the bonding thickness.
What is the difference between one-component polyurethane and two-component polyurethane?
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Firstly, the isocyanate group in one - component polyurethane reacts with moisture to form a membrane. Two - component polyurethane has two parts: one part is isocyanate, and the other part is polyol or polyamine, and these two components react with each other to form a membrane. Secondly, due to the difference in the reaction mechanism, the sensitivity to atmospheric conditions is also different. For one - component PU, high moisture and temperature can increase the reaction speed. In contrast, two - component PU has better storage stability, and its reaction speed is hardly affected by moisture.
What is the advantage for liquid applied membrane (coating)?
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It is suitable for various type of structures and substrates, it can form seamless membrane without joint (seams and joints are the most vulnerable to leakage), and is beneficial for complex structures. The liquid coatings has various functions, sucha as flexible, high strength, excellent abrasion resistance, high load bearing property, and breathable capability, etc.
