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Why does optical brightener KCB apply to EVA


Optical Brighteners KCB is mainly used for whitening synthetic fibers and plastic products and has obvious brightening effect on colored plastic products. It is widely used in plastic films, film pressing molding materials, injection molding materials, etc.


Especially in the production process of EVA foam shoe materials, the addition of fluorescent whitening agent KCB has an excellent whitening effect. However, many people may wonder why Optical Brighteners KCB is recommended for EVA foam shoe materials because there is no significant difference in the color and luster of so many types of brighteners.



From the perspective of temperature tolerance


According to the different use characteristics of various plastics, plastics can be divided into three types: general plastics, engineering plastics and special plastics. However, these three types of plastics cover hundreds of types such as PP, PVC, EVA, PE, PC, PPS, etc. Some plastics have relatively high temperature during the manufacturing and molding process, which requires certain temperature resistance of Optical Brighteners.

When we judge which Optical Brightening agent a plastic is suitable for, we first need to judge from the molding temperature. The molding temperature of EVA material is about 210-230℃, which excludes many plastic fluorescent whitening agents with temperature resistance lower than 210℃.


The plastic fluorescent whitening agents resistant to 210℃ on the market are:


Model temperature tolerance limit

OB-1 359℃

KCB 215℃

KSN 275℃

FP-127 220℃


From that point of view of color light

Optical Brighteners gives off some blue and some red color light. only from the aspect of temperature resistance, whitening agent KCB does not account for too much advantage. at this time we will look at its color light.


Model color tone

OB-1 blue

KCB blue

KSN red

FP-127 blue purple


We Asians usually like blue light and Europeans like red light, so our domestic manufacturers of EVA foam shoe materials mainly use fluorescent whitening agents that emit blue light. Optical Brighteners KCB has certain advantages in terms of color light.


From the perspective of stability


OB-1 is the whitening agent with the largest market share in plastics. OB-1 is resistant to high temperature and its color light is blue. However, one of the biggest problems is that instability will precipitate, which will easily lead to yellowing and green on the surface of the product, thus posing a very high risk to EVA shoe factory.


Although FP-127 has excellent whitening effect, the whitening effect is not lasting for EVA shoe materials, even reaching a period of one year in the process of shoe making and selling. Therefore, FP-127 is not suitable for EVA foam shoe materials from this point of view.


The following table shows the stability of plastic fluorescent whitening agents on the market at present:


Model stability

OB-1 difference

KCB strong

KSN strong

FP-127 difference


From a technological point of view


EVA foaming usually has certain requirements on the number and size of bubbles. The bubbles are too large to wear and too small to be elastic. Besides KCB, the other three types of Optical Brighteners will affect the production process. More bubbles will be generated in the foaming process, resulting in shoes with too small bubbles being inelastic and unusable.


To sum up, Optical Brighteners KCB is the first choice forOptical Brighteners EVA foam shoe materials considering the Optical Brighteners’s temperature resistance, color light, stability and process.