What are the methods for testing and evaluating the performance of color shifting pigments?

The methods for testing and evaluating the performance of color shifting pigments include the following aspects. These methods aim to comprehensively assess the performance of color shifting pigments to ensure they meet the expected outcomes in practical applications.

Evaluate the color difference between the pigment and standard samples using a professional color assessment system (such as the CIE*Lab system) or visual comparison.Determine the relative tinting strength by comparing the sample's absorption coefficient with that of a standard. This can be assessed based on the pigment's absorbance, either at the maximum absorption wavelength or across the entire visible spectrum.Typically defined as the area completely covered by a certain amount of pigment, or the minimum thickness required to cover a substrate layer. This is evaluated by measuring the thickness of the pigment coating and observing its covering effect.

Expose color samples to simulated sunlight or xenon lamps and observe the degree of color change. This is usually evaluated using a grading system (e.g., 1-8 scale), with grade 8 indicating the best lightfastness.Simulate the pigment's changes under different environmental conditions using accelerated climate aging tests, solar radiation aging tests, etc., and observe its color stability and changes in physical properties.

Expose color samples to high temperatures and observe color changes and physical property variations. For example, heat resistance can be evaluated by observing the color changes of samples after being left in an injection molding machine barrel.Mix the pigment with distilled water and observe the degree of color filtration in the filtrate. Water resistance is usually graded using a gray scale.Place the pigment in an oily medium and observe its dissolution or migration to assess oil resistance.Expose the pigment to solutions with different pH values and observe its color changes and chemical stability to evaluate its resistance to acids and alkalis.

Assess the pigment's migration by placing colored samples in contact with transparent materials (such as PVC) and observing the contamination of the transparent material after a certain period and temperature. This is usually evaluated using a grading system (e.g., 1-5 scale).Evaluate the pigment's color stability and changes in physical properties during processing and usage. Common testing methods include powder segregation tests and emulsion stability tests.

Prepare color panels by mixing the pigment with liquid resin or plastic and compare the color difference between the sample and standard samples visually or with a computer colorimeter.Use instruments to directly measure color values or sample numbers, such as using a photometer to measure tristimulus values or the CIE standard colorimetry system for evaluation.

These testing and evaluation methods cover various aspects, including basic performance, durability, solvent resistance, migration resistance, quality stability, hue comparison, and color measurement methods of color shifting pigments. By comprehensively applying these methods, the performance of color shifting pigments can be thoroughly evaluated, providing strong support for practical applications.