Plastic products containing white pigment, its optical properties, such as white degree, yellow degree will directly affect the appearance of the plastic products. Therefore, optical performance is an important basis of judging the application feasibility of mechanical activation method of processing titanium pigment in plastic.

(1) The influence of mechanical activation method of processing titanium pigment consumption in whiteness.

We first investigated the relationship between whiteness and titanium pigment content of untreated titanium pigment in PP sample.

When low concentration, the white degree of PP sample rapidly improved with titanium pigment content increasing. But when the mass percent is more than 1.8%, white degree rises slow. From 1.8% to 8%, white degree only increased by 2.8%. This shows that the plastic coloring exists a maximum effective mass percent (Ce). When the pigment mass percent is lower than Ce, the white degree of PP sample rapidly improved with titanium pigment content increasing; When C > Ce, PP sample's whiteness  no longer increases with titanium pigment content increasing. Therefore, in the plastic coloring, the first is to determine the maximum effective quality percentage in the tinting system, and the occurrence depends on the pigment type and resin system. For titanium pigment, the maximum effective mass percentage is about 2% in the PP sample.

We believe that when the pigment quality percentage is less than the Ce, improving the pigment mass percent of plastic can increase the pigment particle number of unit area. Because the white degree depends on the strength of the reflection light, and titanium pigment is a kind of high refractive index material, and the majority of the lights are reflected and refracted. Therefore, to increase the quality percentage of titanium pigment can increase reflection ability of the products to light, and titanium pigment's quality percentage is higher, the higher the white degree. However, when titanium pigment's mass percent reaches to a certain extent, the particle will overlap longitudinally. In this way, the titanium pigment, located under titanium pigment particle surface, will have no reflection action. So, even if it increases titanium pigment's mass percent, it also won't improve whiteness.

We select the same core material, titanium pigment, with the same formula for mechanical activation method of surface treatment, and makes the preparation of titanium pigment be masterbatch, then injectes into PP, PVC, ABS model with the same pigment quality percentage.
We can see, in the different resin systems, products' white degree increases with mechanical activation method of processing pigment's mass percent increasing, which presents the basically consistent rule with mechanical activation method of processing titanium pigment. Due to in mechanical activation method processing pigment, titanium pigment with 30% - 40% of the proportion is covered in the surface of core material, thus the maximum effective mass percent is far higher than that of the untreated titanium pigment.

When mechanical activation method of processing pigment's mass percent is to 2% in the PP sample, the white degree is close with that of untreated titanium pigment in PP sample with quality percentageof 1%, that is to say, the white degree in PP sample containing 2 copies of mechanical activation method of processing titanium pigment is  similar to that containing a untreated titanium pigment in PP sample. Because in this kind of mechanical activation method of processing titanium pigment, titanium pigment in fact is only 40%, therefore, the white degree of titanium pigment mass percent as 0.8% in PP sample is similar to that of titanium pigment mass percent as 1% in PP sample. So, the use of mechanical activation method of processing titanium pigment can save 20% of the untreated titanium pigment.

(2)The influence of mechanical activation method treatment of titanium pigment on the covering power.

We will make all kinds of mechanical activation method of processing titanium pigment into masterbatch, then blow into PE film. Film of pigment quality percentage is 1%. In the 460 nm of wavelength, we select eight test positions using the spectrophotometry to measuring the optical density of each point. At the same time, we measure the thickness of each point, finally convert the optical density of a unit thickness. Test results are shown in table 2. We can see, titanium pigment through mechanical activation method of processing, the covering power reduced. As is known to all, pigment's covering power is determined by pigment crystal structure. Titanium pigment has the strongest covering power. Other pigments, such as coarse whiting, kaolin, magnetic powder and so on are all less than titanium pigment. Therefore, the core is coarse whiting, kaolin, and titanium pigment is cladding layer of mechanical activation pigment, whose covering power will be reduced. Titanium pigment of quality percentage is higher, covering power is stronger.

(3) The influence of mechanical activation method of processing titanium pigment on the whiteness.

From table 1 of the whiteness data,it can be seen that in the conditions of same pigment quality percentage, titanium pigment model whiteness containing mechanical activation method processing is lower than that of untreated titanium pigment template. This is because titanium pigment with high refractive index is coated in the core material surface in the form of single discontinuous film. Although this single cladding mode can control the particle size of titanium pigment processed by mechanical activation method to a certain extent control mechanical activation method processing pigment particle size distribution, but also brought an unignored problem to paint whiteness. Because the light going into the plastic, through the complex reflection, refraction, scattering, and finally part of the strength of the light which is reflected back directly determines the plastic whiteness. The reflected light is stronger, white degree is higher; Reflected light is weaker, white degree is lower. Usually, the diameter of Tio2 is 0.2-0.4 u m, when single titanium pigment is coated in the surface of core material, and light rays passes through the transparent titanium pigment layer into the inner core. Because the core material of refractive index (CaC03, kaolin is about 1.6) is lower than that of titanium pigment to want a little bit small, so it can absorb many more rays of light than titanium pigment. So the titanium pigment processed by mechanical activation method will take in many more rays of light on the whole than untreated titanium pigment on the whole, leading to the reflection light being abated, white degree being reduced.

At the same time, it also can be seen that mechanical activation method of processing titanium pigment's content is lower, so the whiteness of injection sample is also lower. This proves the above idea that white degree depends on the strength of the reflected light, and reflected light depends on the refraction and reflection ability of pigment. Generally speaking, the thicker cladding layer of titanium pigment with high refractive ability, and the stronger refraction ability , and the higher white degree.

(4) The influence of mechanical activation method of processing titanium pigment on the whiteness.

After titanium pigment is mixed by mechanical activation method and common method, PP sample is injected into the same quality percentage by the masterbatch method, and their whiteness is different.

It canbe seen that the white degree of pp sample containing mechanical activation treatment of titanium pigment is higher. We believe that in the ordinary mixing process, hybrid system is transfered through the screw applying shear stress with the resin matrix. This way cannot guarantee the core material, and the cladding material's aggregate is completely opened and evenly dispersed in the resin matrix, but cladding layer cannot cover the surface of the core material in the form of single molecule membrane.

In the mechanical activation method, after the core material processed by mechanical activation, the activity center of particle surface is deepening, forming a new active center on the primary gap of the crystal grain, so that smaller pigment particles forms the mosaic fixation on the core material crysta in accordance with  the best active center distribution forms. Because the core material and cladding material is fixed mosaicly through the charge acting of two kinds of crystal, it ensures the surface adsorption stability of the cladding material in the core material particle. In addition, mechanical activation treatment of pigment with single discontinuous film form of cladding has the uniformity which mechanical mixing method is unable to achieve. This kind of stability, uniformity makes mechanical activation method of dealing with pigment become a feasible method of pigment surface treatment.