Study on application performance of oxidized polyethylene wax in powder coatings

Abstract

In this paper, powder coating was prepared by melt extrusion method with polyester resin and pigment filler used as raw materials, oxidized polyethylene wax (OPEW) as dispersant, triglycidyl isocyanurate (TGIC) as curing agent, monoalkoxy titanate (i-C3H7OTiX3, X stands for fatty acid group, phosphate group, pyrophosphate group, etc.) as coupling agent (Titanate coupling agent covers the surface of inorganic pigment filler in the state of single molecule, replacing the original adsorption of trace water and gas. Meanwhile, the hydrophobic X group of long carbon chain will combine with the base material physically and chemically, effectively improving the interface state between inorganic and organic matter.), leveling agent and benzoin as additives. The gelation time of the powder coating was tested by a gelation time meter. The gloss of the coating film was tested by a gloss meter. The influence of the OPEW on the gelation time and gloss of the powder coating was investigated. The structure changes of the powder coating before and after solidification were analyzed by Fourier transform infrared spectroscopy (FT-IR). Scanning electron microscopy (SEM) was used to observe the dispersibility of OPEW on pigments and to explore the effect of OPEW types and dosages on dispersibility. Differential Scanning Calorimetry (DSC) analysis and thermogravimetric analysis (TG) were used to analyze the effect of OPEW on the thermal properties of powder coatings. The influence of OPEW on the hardness, impact property and adhesion of solidified film of powder coating was analyzed by mechanical property test. The results show that the gelation time of powder coatings decreases with the increase of OPEW content. This is because OPEW has the function of extinction. Due to the extinction of OPEW, the glossiness of powder coatings decreases with the increase of OPEW content. OPEW promotes the dispersion of pigments and fillers in powder coatings, and when the content of OPEW is 8 wt%, the dispersion performance of pigments and fillers is the best. OPEW improves the hardness, impact performance and adhesion of the film. The relevant film has excellent mechanical properties: hardness can reach 6H + 1750 g, impact performance is 50 cm, adhesion is level 0. The torque of powder coatings containing OPEW is lower than that of powder coatings without OPEW, and the time of torque balance is shorter. OPEW could improve the Tg of the coating. Because OPEW improves the dispersion of pigments and fillers in the system, it makes the mixing of polyester resin, pigments and fillers more uniform, and increases the molecular attraction among them. OPEW can increase the initial decomposition temperature T0 and the maximum decomposition rate temperature of the coating film and increase the maximum use temperature. However, excessive addition of OPEW would affect the final stability, and the stability of the OPEW-2 wt% sample is best. OPEW-0 wt%, OPEW-2 wt% and OPEW-5 wt% powder coatings have the best water resistance.