The plastic modification formula may seem simple, but there are hidden mysteries. This requires us to be cautious when choosing plastic additives. So, how to obtain a formula with higher performance, low cost, and easy processing? Today, I will introduce the selection of additives to you from the following six aspects.

01 Select additives according to purpose

Improve processing performance: lubricants, release agents, stabilizers, processing aids, thixotropic agents, plasticizers, PVC stabilizers.

Improving mechanical properties: plasticizers, reinforcing fillers, toughening agents, impact modifiers.

Improve optical properties: pigments, dyes, nucleating agents, fluorescent brighteners.

Improve aging performance: antioxidants, PVC stabilizers, UV absorbers, fungicides, and mold inhibitors.

Improve surface performance: anti-static agent, smoothing agent, wear-resistant agent, anti adhesion agent, and anti fog agent.

Reduce costs: diluents, fillers.

Improve other properties: foaming agents, combustion aids, chemical crosslinking agents, coupling agents, etc.

02 Additives have selectivity for resins

Red phosphorus flame retardant is effective for PA, PBT, and PET; Nitrogen based flame retardants are effective for oxygen-containing compounds such as PA, PBT, PET, etc;

The heat-resistant modification of glass fiber has a good effect on crystalline plastics, but a poor effect on amorphous plastics;

Carbon black filled conductive plastic has a good effect in crystalline resins;

Nucleating agents have good effects on copolymerized polypropylene.

03 Compatibility between additives and resins

The compatibility between additives and resin is good, so as to ensure that the additives and resin are dispersed according to the expected structure, ensure the completion of design indicators, and ensure that their effects are long-lasting throughout their service life, resistant to extraction, migration, and precipitation.

Except for a few additives such as surfactants, good compatibility with resins is the key to achieving their effectiveness and increasing the dosage. Therefore, efforts must be made to enhance or improve its compatibility, such as using compatibilizers or coupling agents for surface activation treatment.

04 Shape selection of additives

The reinforcing effect of fibrous additives is good. The degree of fibrosis of additives can be expressed by the aspect ratio. The larger the aspect ratio, the better the reinforcement effect. This is why we add glass fiber from the exhaust hole.

The molten state is more conducive to maintaining the aspect ratio and reducing the probability of fiber breakage compared to powder state.

The spherical additive has good toughening effect and high brightness. Barium sulfate is a typical spherical additive, so it is used for filling high gloss PP, and can also be used for small rigid toughening.

Particle size selection of 05 additives

The effect of additive particle size on mechanical properties: The smaller the particle size, the more beneficial it is for the tensile and impact strength of the filling material.

The effect of particle size of additives on flame retardancy: The smaller the particle size of flame retardants, the better their flame retardancy effect. For example, the smaller the particle size of hydrated metal oxides and antimony trioxide, the less amount of additives needed to achieve the same flame retardant effect.

The effect of additive particle size on color matching: The smaller the particle size of the colorant, the higher the coloring power, the stronger the covering power, and the more uniform the color. However, the particle size of colorants is not necessarily as small as possible, as there is a limit value that varies depending on the performance. For chromaticity, the maximum particle size of azo colorants is 0.1 μ m. The maximum particle size of phthalocyanine colorants is 0.05 μ M. For coverage, the maximum particle size of the colorant is 0.05 μ About m.

The effect of additive particle size on conductivity: Taking carbon black as an example, the smaller its particle size, the easier it is to form a network of conductive pathways, achieving the same conductivity effect. The amount of carbon black added is reduced. But like colorants, the particle size also has a limit value. If the particle size is too small, it is easy to aggregate and difficult to disperse, but the effect is not good.

06 Amount of additives added

The appropriate amount of additives is not only to improve the target resin to the appropriate performance, but also based on the economic foundation of low cost. The requirements for adding different additives vary:

(1) Flame retardant, toughening agent, magnetic powder, barrier agent, etc. Although the more amount added is better from a performance perspective, the cost must also be determined;

(2) Conductive additives usually form a circuit path;

(3) An anti-static agent can form a discharge layer on the surface;

(4) Coupling agent can form surface coating.