TiO2 – delustrant in polyester fibers
Because polyester fiber has a smooth surface and a certain degree of transparency, the aurora will be produced under sunshine. The aurora will create strong lights which are not friendly to the eyes. If fiber is added by little material with a different index of refraction, the lights of fiber will diffuse to different directions. Then fibers become darker. The method of adding material is called delustering and the material is called delustrant.
Generally, polyester manufacturers tend to add delustering agent into their products. The commonly-used delusttrant is called titanium dioxide (TiO2). Because its refractive index is double of terylene. The delustering working principle mainly lies in the high refractive index. The bigger difference between TiO2 and terylene is, the better effect of refractive is. At the same time, TiO2 enjoys the advantage of high chemical stability, insoluble in water, and unchangeable at high temperature. What’s more, these characteristics will not disappear in post-treatment.
There is no titanium dioxide in super bright chips, about 0.10% in bright ones, (0.32±0.03)% in semi-dull ones,s and 2.4%~2.5% in full-dull ones. At Decon, we can produce the four types of polyester chips according to customers’ requirements.
Classification of TiO2
According to the crystal structure, industrial TiO2 can be divided into Anatase type and Rutile type. Anatase type has a compact structure, high relative density, and strong tinting strength. But it can not be used as a flatting agent, because its hard granule will wear and tear spinneret plate and diffusion knife very easily. While rutile one is very loose, white, and easy to disperse, so it is very suitable to act as delustrant in the chemical fiber industry.
Usage of TiO2
The average diameter of textile-grade titanium dioxide is 0.35㎛. The particle of TiO2 is very slim and its superficial area is very large. As a result, any good quality titanium dioxide will flocculate or condense into a big particle cluster. So TiO2 must be grinded before usage. If not, it will have a poor dispersity, which leads to uneven dispersion of particles in fibers, a bad delustering effect, and even hairiness and breakage problem in yarn. After grinding, flocculated TiO2 will disperse again.