The influence of coupling agents on the heat resistance, dispersion and reflection properties of pigments

To enhance the applicability of pigments in high-temperature coating industries, this study employed coating and coupling agent modification. After coating and modification with silane coupling agents (KH560/KH570), pigments exhibited minimal color deviation (Δ E < 3) and elevated thermal decomposition temperatures. After baking at 240°C, the Δ E was about 5. The solar and near-infrared reflectance of pigments after modification with KH560 and KH570 did not change significantly, and the near infrared reflection (NIR) reached about 70%, while the NIR value of pigments after modification with stearic acid, titanate and aluminate coupling agents decreased to 63%. The modified effect of KH570 was best. In the zeta potential test, after coating, the pH value corresponding to the isoelectric point of the pigment decreased from 3.23 to 2.66. The modification of coupling agents slightly increased the isoelectric point of the coated pigment, but it was still lower than that of iron oxide yellow pigment. The greater the difference between the pH of the pigment system and its isoelectric point, the better the stability of the pigment system. By coating and modifying with silane coupling agent KH570, the heat resistance and dispersibility of the pigment have been improved.