Robust UV-curable polyurethane acrylate coating

During a new study, a UV-curable self-healing transparent polyurethane acrylate coating based on disulfide bonds and hardened the coating by modified nano-silica was designed.

A laboratory.
Both polyols and amphiphilic ionic liquids showed a sufficient plasticising effect.  Image source: FreeProd - Fotolia (symbol image).

UV-curable coatings have been widely used because of their environmental friendliness and low emission of volatile organic compounds (VOCs). However, the fast curing-speed of UV-curable coatings often leads to internal structural defects, which greatly restricts its application and development. The coating prepared in the recent study shows 93 % scratch repair efficiency under UV light at 50 °C, and the coating has high hardness (4H). In addition, the coating exhibits good transparency (85 % transmittance in the visible region), which means that the coating can meet the requirements of the applications of transparency protective coating.

Broadened application of UV-curable coatings

The defect that blending inorganic particles will hinder the movement of molecular chain was overcome owing to the modified nano-silica (SiO2-KH570) is not simply mixed with the other components but grafted onto the chain. Therefore, the addition of SiO2-KH570 not only harden the coating, but also can reduce the glass transition temperature of the coating which is helpful for self-healing of the coating. Additionally, it was proven that the introduction of disulfide reversible bonds is helpful to eliminate internal stress of UV-curing materials by preheating process, in which the mechanical properties of the coating with disulfide bonds significantly improved (increased by at most 209 %). As the developers point out, their study broadens the application of UV-curable coatings and is expected to address the problem of internal stress defects in UV-curable materials.

The study has been published in Progress in Organic Coatings, Volume 172, November 2022.

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