The thermal stability and light resistance of PVC are poor. At 140 ℃ starts to break down to hydrogen chloride, so choose colorants cannot and its adverse reactions. In addition, the influence of pigment on PVC is reflected in whether the pigment reacts with PVC and other components of PVC products, as well as the resistance and heat resistance of the pigment itself. Therefore, in the case of PVC coloring, considering the characteristics of the resin and related auxiliaries, combined with the characteristics of pigment. The following questions should be noted when choosing a colorant.
Some of the ingredients in the colorant may lead to the degradation of the resin. Iron and zinc ions are catalysts for degradation of PVC resin. Therefore, using iron oxide (red, yellow, brown and black) pigment or zinc oxide, zinc sulfide and lide powder will reduce the thermal stability of PVC resin. Some colorants may interact with the degradation products of PVC resin. If the pigment of group green pigment is resistant to acid, it will lose its color due to the interaction of hydrogen chloride produced by the decomposition of PVC during the dyeing process of PVC.
Migration occurs only in plasticized PVC products and is used in the use of dyes or organic pigments. Is part of the so-called migration is in the surrounding solvent soluble dyes or organic pigments, through the surface of plasticizer penetrated into PVC products, the dissolved dye (yan) material particles also was taken to the products on the surface, in this way, lead to bleeding, solvent bleeding after solution or frosting. Another problem is scaling. Refers to the colorants in the coloring process, because of being shaded intermiscibility poor or not compatible and free from the system, deposited on the surface of the processing equipment (such as extruder barrel lining, die hole wall).
The ability of pigment to withstand various climates. These include visible and ultraviolet light, water, temperature, chlorination of the atmosphere and chemicals encountered during the use of the product. The most important weather-resistance, including fastness, pulverization and durability of physical properties. Organic pigments are different because of their structure. In addition, in the formulation containing white pigment, the weatherability of pigment will be seriously affected.
The discoloration, darkening, or color change of pigments, usually caused by the reaction genes of pigments. These reactive genes can interact with water or chemicals in the atmosphere -- acids and bases. Cadmium yellow, for example, under the action of water and sunlight fade, lithol red has good light resistance, suitable for most indoor application, outdoor use in acid, alkali ingredients when serious fade. Dehydrochlorination according to JIS - K - 6723, the determination methods of measuring temperature 180 ℃. The time of the uncolored polyvinyl chloride (PVC) polyvinyl chloride was used as the baseline, and the delay time was 5% and 10% interval, and the negative value indicated accelerated decomposition.