How to choose polyethylene wax in color masterbatches?

2022-01-10   Pageview:98

Polyethylene wax, as a fine chemical material, is widely used in plastic and rubber processing and in the production of coatings and inks. Polyethylene wax is compatible with polyethylene and polypropylene, and can improve the fluidity of polyethylene, polypropylene and ABS and the demoulding of polymethyl methacrylate and polycarbonate. In PVC processing, compared with microcrystalline wax, polyethylene wax has stronger external lubrication effect. In addition, polyethylene wax can also be used in inks, coatings, paper and hot melt adhesives.

Polyethylene wax is specifically for masterbatch processing and is an important raw material to solve the problem of pigment or filler dispersion in masterbatches. The selected polyethylene wax must have good compatibility with resin to avoid migration; have excellent thermal stability to avoid decomposition in the subsequent processing and quality problems.

Polyethylene wax is mainly used in polyolefin masterbatches, including polyethylene masterbatches, polypropylene masterbatches and EVA masterbatches.

Homopolymerized polyethylene wax is mainly used in polyolefin masterbatches as pigment wetting and dispersing agent. It is mainly used for wetting, dispersing, mixing and stabilization of pigments after dispersion.

In the masterbatch, the amount of pigment or filler is very large, plus the particle size of these pigments and fillers are very small, in the range of 0. 01~1. 0μm, so it is easy to agglomerate. By adding homopolymerized polyethylene wax, the polyethylene wax melts in a certain temperature range and can wet the pigment or filler surface. The so-called pigment wetting is the process by which the molten polyethylene wax is held close to the surface of the pigment particles and penetrates into the fine voids of the pigment particles by capillary action to replace the air and moisture in its original position.

The initial wetting of the pigment is of irreplaceable importance to the outcome of the pigment dispersion, but this process is usually accomplished in a few seemingly simple steps and is therefore easily overlooked. The wetting agent must make sufficient capillary penetration between the microgaps in the pigment particle aggregates, due to the capillary penetration, the cohesion between the pigment particles is reduced, and it is easily crushed and refined under the action of shear force. Therefore, the wetting rate and the degree of capillary penetration of the pigment play a decisive role in the total dispersion rate and quality of the pigment particles. If the wetting effect is good, the pigment aggregates can be easily dispersed even with a weak shear. Once the pigment aggregates are dispersed, the wax covers the newly created pigment free surface and stabilizes the pigment dispersion, which is how polyethylene wax works as a pigment dispersing wetting agent.

Therefore, the principles of polyethylene wax as a masterbatch dispersant are selected as follows.

Appropriate molecular weight – viscosity of polyethylene wax.

A narrower molecular weight distribution.

Better wetting ability.

Higher heat resistance.

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