Abstract
Recent studies have indicated that the addition of a diluent significantly affect its mechanical properties and performance of a coating, but no works have been reported on the influence of diluent content on the Young’s modulus of a coating, and the evolution law between them is also not clear. To address the deficiency, polyurethane coatings (paint samples) with different diluent contents were prepared. Force-displacement curves and microscan images of the coatings were obtained by atomic force microscopy, and the Young’s modulus of the coatings was calculated on the basis of the indentation method, and positron annihilation lifetime spectroscopy was used to test the microstructure of the coatings. The results reveal that: (i) Young’s modulus of the coating initially increase and then decreases with diluent content increasing; (ii) the free-volume aperture size had a greater effect on Young’s modulus by grey correlation analysis.
Highlights
Saalah et al [11] studied the effect of the extent of OH in polyols on the mechanical properties of polyurethane coating, and the results showed that the Young’s modulus increased with an increase in the number of hydroxyl groups. is was attributed to the higher concentration of OH groups providing more cross-linking sites for the formation of hydrogen bonds on hard segment chains
E study described designed paint systems with different diluent contents and prepared corresponding polyurethane coatings by a spin-coating method. e forcedisplacement curve between the probe and the coating was measured by atomic force microscopy (AFM) [22]
Grey relation theory was applied to analyze the influence of microstructure indexes on the Young’s modulus. e method proposed in this paper can accurately calculate the Young’s modulus of the coating, and the test results of its microscan images have the same variation trend as those obtained by the method. e following conclusions can be reached: (i) Young’s modulus of polyurethane coating increases firstly and decreases with increasing diluent content
Summary
Among the many mechanical performance indexes of a coating, the Young’s modulus is one of the most critical and represents the relationship between elastic deformation and applied stress [6]. Saalah et al [11] studied the effect of the extent of OH in polyols on the mechanical properties of polyurethane coating, and the results showed that the Young’s modulus increased with an increase in the number of hydroxyl groups. Hwang et al [12] found that increasing the crosslinking density of polyurethane reduced the fluidity of the chain segment, providing improved resistance to external tensile force, increasing the elastic modulus of the coating, and reducing the deformation when subjected to an external load. The relationship between the free volume indexes and the Young’s modulus of each coating was quantitatively determined using grey relation theory
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