How to choose polyethylene wax in masterbatch formulation?
Polyethylene wax plays a role of lubrication and dispersion in the masterbatch system, increasing the compatibility of pigments with resins such as polyethylene, polyvinyl chloride, and polypropylene etc. It is helpful to improve extrusion efficiency of masterbatch and increase product surface gloss and processing performance.
The choice of polyethylene wax in the masterbatch formula needs to consider both the pigment and the carrier resin in the masterbatch, and also consider the resin to be colored. According to the similar compatibility principle, homopolyethylene wax is suitablefornonpolar plastics, such as polyethylene and polypropylene, while molecules of copolymerized polyethylene wax are connected with polar groups to introduce carboxyl groups, and then esterified modification etc., so it is suitable for polar polyvinyl chloride, polystyrene, ABS, and engineering plastics. The selected polyethylene wax can only be mixed and dispersed with each other when they have good compatibility with the carrier resin. In the same way, the selection of polyethylene wax is also suitable for polarity matching of various pigments.
Polyethylene wax has wetting and dispersing functions in masterbatch processing. The viscosity of an ideal wetting and dispersing agent in its wetting stage of pigment particles (relatively low temperature) is relatively low, and it is helpful to the wetting of pigment particles. The viscosity in the shear dispersion stage (relatively high temperature) is expected to be higher, so that its help for shear dispersion will be more obvious. However, if the viscosity is too low, it is not helpful to disperse when the shear force is the main for pigment dispersion。
In conventional processing, increasing the temperature of the dispersion system is helpful for the wetting and penetration of pigment particles. Reducing the temperature is more helpful for the shear dispersion. How to find the processing conditions and methods of effective disperse is what we must seriously consider and treat, so we need to consider comprehensively and systematically and select the appropriate polyethylene wax.
Polyethylene wax selection needs to consider the environment and product safety etc. Wax products with too low molecular weight will improve volatility and cause environmental pollution and product odor etc. If such wax is used in some sensitive applications such as food packaging materials, children's toys etc., it will cause very serious adverse consequences. So its selection must be cautious.
Choose different kinds of polyethylene waxes from the end customer. If masterbatches are used for lowend applications such as garbage bags, trash cans, mulch films etc., customers can choose byproduct wax or cracking wax. If masterbatches are used in midrange applications and have dispersion and taste requirements, customers can choose synthetic polyethylene waxes. If the masterbatch is used for special applications, where taste and heat resistance are critical, then choose ZieglerNatta or metallocene polymerized polyethylene wax. At this time, the choice of polyethylene wax is not only a kind of dispersant, but also other requirements from the end application.