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Selection of Modified Plastic Additives


Plastic recipe design surface looks very simple, but in fact contains a lot of internal links, in order to design a high-performance, easy processing, low-cost formula, the choice of additives need to consider a lot of factors, are the following aspects of the factors for reference:

First, according to the purpose to achieve the use of additives

According to the purpose to achieve the choice of appropriate additives varieties, the additives should be able to give full play to its expected effect, and meet the required indicators. Specified indicators are generally national standards for products, international standards, or customer performance requirements. Auxiliaries are selected as follows:

Toughening - optional elastomers, thermoplastic elastomers and rigid toughening materials.

Enhanced - optional glass fiber, carbon fiber, whisker and organic fiber.

Flame retardant - bromine (ordinary bromine and environmental bromine), phosphorus, nitrogen, nitrogen / phosphorus composite intumescent flame retardant, antimony trioxide, hydrated metal hydroxides.

Antistatic - all kinds of antistatic agents.

Conductive - carbon (carbon black, graphite, carbon fiber, carbon nanotubes), metal fibers and metal powders, metal oxides.

Magnetic - ferrite magnetic powder, rare earth magnetic powder, including samarium cobalt (SmCo5 or Sm2Co17), NdFeB (NdFeB), samarium iron and nitrogen (SmFeN), aluminum and nickel cobalt magnetic powder three categories.

Thermal conductivity - metal fibers and metal powders, metal oxides, nitrides and carbides; carbon materials such as carbon black, carbon fibers, graphite and carbon nanotubes; semiconductor materials such as silicon and boron.

Heat-resistant glass fibers, inorganic fillers, heat-resistant agents such as substituted maleimides and β-crystal nucleating agents.

Transparent - nucleating agent, for the PP alpha crystal nucleating agent sorbitol series Millad 3988 the best.

Wear-resistant graphite, molybdenum disulfide, copper powder and so on.

Insulation - calcined kaolin.

Barrier - mica, montmorillonite, quartz and so on.

Second, the additive is selective for the resin

Red phosphorus flame retardant for PA, PBT, PET effective; nitrogen flame retardant effective for oxygen, such as PA, PBT, PET, etc .; nucleating agent on the effect of copolymer polypropylene; glass fiber heat modified to crystallization Plastic effect is good, poor effect on the amorphous plastic; carbon black filled with conductive plastic, the effect of good in the crystalline resin.

Third, the form of additives

The same composition of the additives, its different shape, the role of the modification of a great impact.

1, the shape of additives

Fibrous auxiliaries to enhance the effect of good. The degree of fibrosis of the auxiliaries can be expressed in terms of aspect ratio, the greater the L / D, the better the enhancement effect, which is why we add glass fibers from the vent. The molten state is better than the powder to maintain the aspect ratio, reducing the probability of broken fiber.

Spherical auxiliaries toughening effect is good, high brightness. Barium sulfate is a typical spherical additive, so high-gloss PP filled with barium sulfate, a small degree of rigidity toughening can also be barium sulfate.

2, the particle size of additives

A. Effect of particle size on mechanical properties

The smaller the particle size, the more beneficial the tensile strength and impact strength of the filler material.

B. Effect of particle size on the flame retardancy

The smaller the particle size of the flame retardant, the better the flame retardant effect. For example, the smaller the particle size of the hydrated metal oxide and antimony trioxide, the less the amount of addition of the same flame retardant effect.

C. Effect of Particle Size on Color Matching

The smaller the particle size of the colorant, the higher the tinting power, the stronger the hiding power, the more uniform the color. But the particle size of the colorant is not as small as possible, there is a limit value, and the different limits of different performance. For the color strength, the limiting particle size of the azo type colorant was 0.1 m, and the limiting particle size of the phthalocyanine colorant was 0.05 m. For the hiding power, the limiting particle size of the colorant is about 0.05 m.

Effect of Particle Size of Auxiliaries on Conductivity

To carbon black, for example, the smaller the particle size, the more likely to form a network of conductive pathways to achieve the same conductive effect by adding the amount of carbon black. But with the same color, the particle size also has a limit, the particle size is too small easy to gather and difficult to disperse, the effect is not good.

3, the surface treatment of additives

Additives and resin compatibility is better, so as to ensure that the auxiliary agent and resin in accordance with the expected structure of the dispersion to ensure the completion of the design indicators to ensure that the effect of its long-term use of life, resistance to extraction, resistance to migration, resistance to precipitation. Such as most of the recipe requires additives and resin evenly dispersed, the barrier formula is expected to additives in the resin layered distribution. In addition to a small number of surfactants and other additives, and resin compatibility is to play its effectiveness and increase the amount of the key. Therefore, it is necessary to try to improve or improve its compatibility, such as the use of compatibilizer or coupling agent for surface activation treatment.

All inorganic additives on the surface after treatment, the modification effect will be improved. Especially in the most obvious filler, there are other glass fiber, inorganic flame retardants and so on.

The surface treatment is mainly based on coupling agent and compatibilizer, and the coupling agent is specific as silane, titanate and aluminate, and the compatibilizer is the corresponding maleic anhydride graft polymer.

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