The hiding power of carbon fiber primer is one of its core performance indicators, directly affecting the coating's coverage of the substrate color and the uniformity of the final appearance. Its strength is not determined by a single factor, but rather by the combined effects of pigment characteristics, formulation design, application techniques, and environmental conditions.
As the core carrier of hiding power, the type and particle size distribution of pigments play a decisive role in performance. Inorganic pigments, such as titanium dioxide, due to their high refractive index (approximately 2.7), create a significant difference in light scattering compared to paint, making them the preferred choice for enhancing hiding power, especially in white systems. Organic pigments, with a refractive index close to that of paint (approximately 1.5-1.7), have weaker hiding power and are mostly used for tinting or transparent coatings. Pigment particle size refinement is another key factor. Micron-sized particles (such as nano-titanium dioxide) significantly improve light scattering efficiency by increasing the number of scattering points per unit volume; however, excessive refinement may lead to agglomeration, which reduces hiding power. Furthermore, pigment concentration needs to strike a balance between hiding power and leveling properties; excessively high concentrations can easily cause coating cracking, while excessively low concentrations will fail to completely cover the substrate.
Formulation design optimizes hiding power through the synergistic effect of resins and additives. As the dispersion medium for pigments, the molecular structure of the resin directly affects the dispersion stability of the pigments. Highly polar resins (such as epoxy resins) enhance the interaction with pigments, preventing sedimentation and agglomeration, and ensuring uniform hiding power distribution. Solvent selection must balance evaporation rate and solubility. Fast-drying solvents can shorten the application cycle, but excessive evaporation may cause surface shrinkage and pinholes; slow-drying solvents, while improving leveling, may prolong drying time and increase the risk of dust adsorption. Dispersants in the additive system promote uniform dispersion by reducing pigment surface tension; leveling agents indirectly improve hiding power by adjusting coating surface tension, eliminating brush marks and orange peel.
The application process affects hiding power throughout the entire coating process. In carbon fiber primer spraying, high-pressure airless spraying offers superior hiding power compared to traditional air spraying due to uniform paint atomization and a denser coating; however, excessive pressure may cause paint rebound, resulting in localized thin coatings. The distance and speed of the spray gun must be strictly matched to the characteristics of the coating. Too much distance results in coating dispersion and reduced hiding power; too fast a movement leads to insufficient coating thickness and the substrate color showing through. Multi-layer thin-spraying avoids sagging and ensures progressively increasing hiding power by stacking layers, but the drying time of each layer must be strictly controlled; otherwise, insufficient interlayer adhesion may lead to peeling. Regarding the construction environment, excessively high temperatures accelerate solvent evaporation, causing the coating to cure before it is fully leveled, resulting in a rough surface; excessive humidity may cause the coating to whiten, reducing hiding power; poor ventilation can lead to solvent retention, affecting drying speed and coating performance.
The impact of substrate characteristics on hiding power is often overlooked. Due to differences in molding processes, carbon fiber surfaces may have microscopic defects such as pinholes and streaks. These defects can disrupt coating continuity, leading to localized reductions in hiding power. Therefore, before coating, surface defects must be eliminated through mechanical grinding or chemical treatment to increase roughness and enhance coating adhesion. Furthermore, the color depth of the substrate directly affects the required hiding power; dark substrates require higher pigment concentrations or more layers to achieve the same hiding power.
Optimizing the hiding power of carbon fiber primer requires a multi-dimensional approach, encompassing pigment selection, formulation design, application control, and substrate treatment. By selecting high-refractive-index inorganic pigments, optimizing the resin and additive system, strictly controlling application parameters, and pre-treating the substrate surface, hiding power can be significantly improved, ensuring uniform and durable coatings that meet the dual requirements of appearance and performance in high-end applications.
