Comparison between epoxy porcelain-like coatings and hand-applied elastomeric polyurethane coatings

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Epoxy porcelain-like coatings have a non-elastic structure; therefore, their flexibility is far inferior to that of hand-applied elastic polyurethane coatings. Under the impact of gravity, epoxy porcelain-like coatings all crack and flake off. Hand-applied elastic polyurethane coatings, due to their high-elastomer structure, do not experience such issues; as a result, they are more resistant to washing and impact when in use. Regarding the treatment of the surface to be painted, both imported coatings and epoxy porcelain-like coatings have high requirements. If imported coatings are to be applied to cement surfaces, acid treatment is required; epoxy porcelain-like coatings need two layers of base treatment. The surface of the steel plates must be descaled. The surface on which hand-applied elastic polyurethane coatings are applied does not require high standards – it only needs to be dry, free of loose layers, and free from oil stains. Only a layer of primer is required on the cement surface, while no strict rust removal is necessary for ordinary steel surfaces. In terms of application, it is simpler than other coatings. Hand-applied elastic polyurethane coatings are also highly effective waterproof coatings, whose technical performance meets or exceeds the requirements for first-class products as specified in the JC500—92 standard issued by the Ministry of Building Materials. Therefore, hand-applied elastic polyurethane coatings, when used in the upper and lower water tanks of buildings or in concrete pipes and channels, can effectively prevent leakage. Other coatings require a separate waterproofing layer, which increases the project costs and prolongs the construction time. Regarding the curing and drying of coatings, since the imported coatings are water-based, it is difficult for them to dry in the humid weather of March and April in southern China. Hand-applied elastic polyurethane coatings are reactive coatings that are not affected by air humidity; thus, they do not impede the construction process in humid environments. Epoxy porcelain-like coatings are two-component coatings; during application, improper mixing ratios or uneven mixing by the applicators can affect the quality of the coating. If the prepared paint is not used up, it cannot be reused, resulting in waste. Hand-applied elastic polyurethane coatings are single-component coatings; they do not suffer from the aforementioned problems, effectively ensuring construction quality without causing any waste of coating. Hand-applied elastic polyurethane coatings are highly resistant to low temperatures; their performance remains unaffected in environments ranging from -60 to -40°C. Moreover, the performance of many coatings becomes brittle in environments ranging from -60 to -40°C. Therefore, hand-applied elastic polyurethane coatings have a wider range of applications. Since most traditional coatings contain volatile solvents, and the evaporation of these solvents poses risks such as fire hazards, solvent poisoning, and solvent loss, the use of solvents without volatility has been a development trend in coatings over the past few decades. Hand-applied elastic polyurethane coatings have made a significant technical advancement in this direction. Hand-applied elastic polyurethane coatings also hold great potential in terms of technical applications; for example, it is possible to develop a range of high-performance ship coatings (including those designed to reduce drag and save energy on ship hulls), anti-corrosion coatings that can protect against rust, antimicrobial coatings for maintaining cleanliness, and low-temperature waterproof coatings for cold storage facilities. It is therefore a coating type with significant development potential. Due to the different end-capping groups used in hand-applied polyurethanes, most of the isocyanates are not esterified and instead remain as functional groups within the molecular structure. Their lack of freedom to be released makes such coatings non-toxic and harmless, fully meeting the **sanitary standards for coatings used in drinking water applications**. However, the presence of isocyanate functional groups exhibits strong biological sensitization in marine biological cells. Therefore, this type of coating has a special function of preventing the attachment of marine organisms when used on ship hulls.