The surface of the plastic formula design looks very simple, but it actually contains a lot of intrinsic links. In order to design a high-performance, easy-to-process, low-price formula, there are many factors to consider when selecting additives. The following factors are proposed. for reference:
First, select additives according to the purpose to be achieved
According to the purpose to be achieved, select the appropriate auxiliaries, and the auxiliaries should be able to fully exert their expected effects and meet the specified targets. The specified indicators are generally the national standards of the products, international standards, or performance requirements proposed by the customer. The specific selection range of additives is as follows:
Toughening - selection of elastomers, thermoplastic elastomers and rigid toughening materials.
Enhanced - glass fiber, carbon fiber, whisker and organic fiber.
Flame retardant - bromine (common bromine and environmentally friendly bromine), phosphorus, nitrogen, nitrogen / phosphorus composite expansion flame retardant, antimony trioxide, hydrated metal hydroxide.
Antistatic - all kinds of antistatic agents.
Conductive - carbon (carbon black, graphite, carbon fiber, carbon nanotubes), metal fibers and metal powder, metal oxides.
Magnetic-ferrite magnetic powder and rare earth magnetic powder include samarium cobalt (SmCo5 or Sm2Co17), neodymium iron boron (NdFeB), neodymium iron nitrogen (SmFeN), and aluminum nickel cobalt magnetic powder.
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, boron.
Heat resistant - glass fibers, inorganic fillers, heat resistant agents such as substituted maleimides and beta crystal nucleating agents.
Transparent - nucleating agent, the sorbitol series Millad 3988, which has an alpha crystal nucleating agent for PP, works best.
Wear-resistant - graphite, molybdenum disulfide, copper powder, etc.
Insulation - calcined kaolin.
Barrier - mica, montmorillonite, quartz, etc.
Second, the auxiliary agent is selective for the resin
Red phosphorus flame retardant is effective for PA, PBT, PET; nitrogen flame retardant is effective for oxygen-containing, such as PA, PBT, PET, etc.; nucleating agent has good effect on copolymerized polypropylene; glass fiber heat-resistant modification to crystallization The effect of the plastic is good, and the effect on the amorphous plastic is poor; the carbon black is filled with the conductive plastic, and the effect is good in the crystalline resin.
Third, the form of additives
The auxiliaries of the same composition have different effects on the modification.
1, the shape of the auxiliary
The reinforcing effect of the fibrous auxiliary agent is good. The degree of fiberization of the additive can be expressed by the aspect ratio. The larger the L/D, the better the reinforcement effect, which is why we add glass fiber to the vent. The molten state is advantageous for maintaining the aspect ratio and reducing the probability of fiber breakage than the powder.
The spherical auxiliaries have good toughening effect and high brightness. Barium sulphate is a typical spherical auxiliaries, so high-gloss PP is filled with barium sulfate, and a small degree of rigidity and toughness can also be used.
2, the particle size of the auxiliary
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 additive particle size on 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 the antimony trioxide, the less the amount of addition to achieve the same flame retardant effect.
C. Effect of additive particle size on color matching
The smaller the particle size of the colorant, the higher the coloring power, the stronger the hiding power, and the more uniform the color. However, the particle size of the colorant is not as small as possible, there is a limit value, and the limit values for different properties are different. For the coloring power, the ultimate particle size of the azo colorant was 0.1 μm, and the limit particle size of the anthraquinone colorant was 0.05 μm. For the hiding power, the limiting particle size of the colorant is about 0.05 μm.
D. Effect of additive particle size on electrical conductivity
Taking carbon black as an example, the smaller the particle size, the easier it is to form a network-like conductive path, and the same conductive effect is added to reduce the amount of carbon black added. However, like the coloring agent, the particle size also has a limit value, the particle size is too small to be gathered and difficult to disperse, and the effect is not good.
3. Surface treatment of additives
The compatibility of the auxiliary agent and the resin should be good, so as to ensure the dispersion of the auxiliary agent and the resin according to the expected structure, to ensure the completion of the design index, to ensure the long-lasting effect of the effect in the service life, resistance to extraction, migration resistance, and precipitation resistance. If most of the formulations require uniform dispersion of the auxiliaries and the resin, it is desirable for the barrier formulation to be layered in the resin. In addition to a small amount of additives such as surfactants, good compatibility with the resin is the key to its efficacy and increased addition. Therefore, it is necessary to try to improve or improve the compatibility, such as surface activation treatment with a compatibilizer or a coupling agent.
After the surface of all inorganic additives has been treated, the modification effect will be improved. Especially the filler is most obvious, and other glass fiber, inorganic flame retardant and the like.
The surface treatment is mainly a coupling agent and a compatibilizer, the coupling agent is specifically a silane, a titanate and an aluminate, and the compatibilizer is a maleic anhydride graft polymer corresponding to the resin.
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