Fluorescent brightener,Optical brighteners, optical brightening agents (OBAs), fluorescent brightening agents (FBAs), or fluorescent whitening agents (FWAs), is a kind of fluorescent dye, or white dye. It is also a complex organic compound. Its characteristic is that it can excite the incident light to produce fluorescence, so that the dyed material can obtain a glittering effect similar to fluorite, so that the material seen by the naked eye is very white.
A large number of organic materials, natural or man-made textiles or other substances, such as paper and plastics, do not look white. Usually, they absorb more blue and purple light (400 ~ 480nm) than yellow light, so they show a slight yellow more or less.
The fluorescent brightener is dyed to a certain whiteness matrix (such as textiles, plastics, paper, detergent, etc.) by some method. This matrix reflects visible light under the irradiation of sunlight (or a light source containing sufficient ultraviolet light), At the same time, the molecules of Fluorescent Brightener on the matrix absorb the energy of ultraviolet light (about 340 ~ 380nm) invisible to the naked eye caused by sunlight and its characteristic frequency, and then emit in the visible light region of blue purple (about 410 ~ 460nm) in the form of extremely bright fluorescence. This blue purple fluorescence is mixed with the slight yellow light on the substrate (yellow is the complementary color of blue purple) to obtain white light, which has a whitening effect. As the ability of the matrix whitened by the fluorescent brightener to reflect visible light is enhanced, the whiteness and brightness of the matrix are increased, so that the whitened matrix looks white, pleasing and bright. It can also be seen that the whitening of fluorescent brightener is optical complementary brightening.
The amount of fluorescent brightener is usually expressed as a percentage relative to the mass of plastic. The amount of fluorescent brightener in plastic is related to its chemical structure, dispersion and the properties of plasticizer or other additives in plastic formula. The dosage of fluorescent brightener is generally 0.05% ~ 0.1% (for plastic weight), and for ultra white varieties, the dosage can reach 0.5% (for plastic weight) or more; For transparent plastics, the dosage is 1 / 100 ~ 1 / 10 of the above dosage.
The appropriate dosage should be determined through small sample test in order to meet the application requirements. It is not that the more the dosage of fluorescent whitening agent, the better the whitening effect, but that there is a certain concentration limit. If it exceeds a certain limit value, there will be no whitening effect and even yellowing. Excessive use of fluorescent brighteners will cause insolubility, migration and aging resistance.
The combination of two or more different fluorescent brighteners, if properly selected, will broaden the fluorescence spectrum and enhance its fluorescence intensity, achieve the purpose of increasing efficiency and improve its application performance.
In the production process of plastic products, plastic whitening agent plays a key role. The reason why plastic products are very beautiful and bright is that whitening agent is added. However, what kind of whitening agent meets the requirements?
Whitening agents used in plastics are usually insoluble in water and soluble in organic solvents. Adding fluorescent whitening agents to plastics can not only improve the appearance of products, but also effectively improve the weather resistance of products. In the production process of plastic products, due to different product performance, processing characteristics and application requirements, there are also various requirements in the selection of fluorescent brightener.
What are the requirements for selecting fluorescent brightener for plastic products
1. To have a very good whitening effect, the whitening effect of fluorescent brightener is mainly reflected in the whiteness. The high whiteness of brightener can not only reduce the amount of brightener, but also prevent the strength of plastic from changing, so as to reduce the manufacturer's cost.
2. It has excellent high-temperature stability. Generally, the melting temperature of plastics is relatively high, mostly at the high temperature of 150-280 ℃, so the melting point of whitening agent cannot be lower than this range.
3. It has good sun resistance and light resistance. Nowadays, white plastics account for most of the plastics, but most manufacturers will be troubled by the whiteness of white plastics, especially it is easy to turn yellow after sunlight. At this time, when we choose fluorescent brighteners, we require that the brighteners have good sun and light resistance.
4. It has good compatibility with plastics and good dispersion, which is a necessary condition to ensure that plastics are uniformly whitened.
The above points are some simple requirements for the whitening agent used in plastics. In fact, there will be more requirements in the production process of plastic products. Therefore, when you are not sure which type of whitening agent your product should choose, it is better to consult a professional whitening agent factory first, which is more reliable.