The whitening effect of fluorescent whitening agents
The effect of whitening agents is commonly expressed in terms of whiteness, which is not only related to the amount of fluorescent whitening agent added, but also to the compatibility of the resin and the light resistance of the plastic. Fluorescent whitening agents with good compatibility have good and long-lasting whitening effects. The most direct and effective method to test the whitening effect of fluorescent whitening agents is to conduct small sample experiments.
The dosage of fluorescent whitening agent
The amount of fluorescent whitening agent is commonly expressed as a percentage relative to the mass of the plastic. The dosage of fluorescent whitening agents in plastics is related to their chemical structure, dispersion, and the properties of plasticizers or other additives in the plastic formula. The dosage of fluorescent whitening agent is generally between 0.01% and 0.05%. The appropriate dosage should be determined through small sample tests, based on the principle of meeting application requirements. It is not necessarily the case that the more fluorescent whitening agent used, the better the whitening effect. Instead, there is a certain concentration limit beyond which there will be no whitening effect and even yellowing. Excessive amount of fluorescent whitening agent will cause immiscibility, migration and degradation of anti-aging performance.
Using two or more different whitening agents in combination, if chosen appropriately, will widen the fluorescence spectrum, enhance its fluorescence intensity, achieve the goal of increasing efficiency, and improve its application performance.
The influence of pigments in plastic formulas on whitening effect
Since the function of fluorescent whitening agents is to convert ultraviolet light into visible blue or purple light, the components that can absorb ultraviolet light, namely white pigments and ultraviolet stabilizers, have the greatest impact on the fluorescent whitening agents themselves. Titanium dioxide in white pigments can absorb 380nm light waves in ultraviolet light. If it is present in plastic products, it will reduce the whitening effect of fluorescent whitening agents. Due to the different absorption of 380nm light waves by different crystal forms of titanium dioxide, anatase type can only absorb 40% of 380nm light; Rutile type can absorb 90%. If titanium dioxide and fluorescent whitening agent are used together, rutile type titanium dioxide should be selected and the amount of fluorescent whitening agent added appropriately.
Post time: Nov-20-2024