The dispersant should have good compatibility with resin and good affinity with pigment, which can make the pigment evenly dispersed and no longer cohesive.
It is more reasonable to choose polyethylene wax as pigment wetting agent. According to the theory of dispersion and wetting, the viscosity of wetting agent and the number of functional groups have a crucial influence on the wetting and dispersing effect of pigment. The viscosity of the wetting agent is relatively low to facilitate the wetting of the pigment. Take polyethylene wax as an example, a simple way to distinguish is to choose the relative density of 0. 91-0. 93 polyethylene wax, its viscosity is relatively low, and the final dispersion effect is ideal; while when the relative density is 0. 94 or above, its viscosity is obviously high, and the pigment wetting effect is poor, because polyethylene wax is a typical external lubricant at the same time as the wetting and dispersing agent, and when its density is too high, its viscosity in the system will be greatly enhanced. When its density is too high, it will greatly strengthen its lubricity in the system and is not conducive to the dispersion of pigments.
(2) Molecular weight distribution of polyethylene wax
This is a very important consideration. If the molecular weight is too large, the viscosity of the wax is too high, which will definitely affect the wetting effect; while if the molecular weight is too small, the viscosity of the wax is too low, which will lead to the reduction of the viscosity shear ability of the system and affect the dispersion.
(3) Technical index of polyethylene wax
Need to pay attention to the “low temperature viscosity” and “high temperature viscosity” of polyethylene wax, here the “low temperature” and “high temperature “refers to the relative temperature concept. Ideally, the viscosity of polyethylene wax is relatively low when it is wetting the pigment particles (relative low temperature), which is good for the wetting of pigment particles; the viscosity is higher when it is shearing and dispersing (relative high temperature), which will help the shearing and dispersing more obviously. So read the technical indexes of polyethylene wax products carefully, which is beneficial to the selection of polyethylene wax products.
(4) The fineness of polyethylene wax product powder
Finer polyethylene wax powder can quickly complete the melting process in the equipment, that is to say, the pigment particles can be wetted earlier and enter the process of wetting and dispersing, which also effectively improves the speed of wetting; so the micronized wax is more favored by the industry.
(5) Environmental and product safety factors
Wax products with too low molecular weight can increase volatility and cause environmental pollution and product odor, etc. If such wax is used in some sensitive applications, such as food packaging materials, it can cause very serious adverse consequences, so the choice of such a major auxiliary material must be carefully.
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