Key points for the selection of modified plastic additives
Although the plastic formula design appears straightforward at first glance, it really has several internal connections. When choosing additives, there are a variety of aspects to take into account in order to build a formula with high performance, simple processing, and cheap cost. The following elements are suggested here as a guide:
Choose additives based on the goal to be attained.
The sort of auxiliaries to be added should be chosen based on the goal to be accomplished, and they should be able to completely exert their anticipated effects and achieve the designated indications. The product's national and international standards, as well as any performance specifications put out by clients, are often the stated indications. The following is the precise selection range for additives:
Elastomers, thermoplastic elastomers, and stiff toughening compounds are good choices for toughening.
Choose from glass fibers, carbon fibers, whiskers, and organic fibers for reinforcement.
Flame retardants include antimony trioxide, hydrated metal hydroxide, phosphorus, nitrogen, and composite intumescent flame retardants made of nitrogen and phosphorus.
There are several antistatic agents.
Carbons (carbon black, graphite, carbon fibers, and carbon nanotubes), metal fibers and powders, and metal oxides all have conductivity.
Magnetic——Samarium cobalt (SmCo5 or Sm2Co17), neodymium iron boron (NdFeB), samarium iron nitrogen (SmFeN), and alnico magnetic powder are examples of ferrite magnetic powder and rare earth magnetic powder.
Metal fibers and powders, metal oxides, nitrides, and carbides; carbon-based materials including carbon black, carbon fibers, graphite, and carbon nanotubes; semiconductor materials like silicon and boron are all examples of materials that carry heat.
Glass fibers, inorganic fillers, heat-resistant substances such substituted maleimides, and crystal-nucleating agents are some materials that are heat-resistant.
For PP, the sorbitol series Millad 3988 of crystal nucleating agents works well as a transparent - nucleating agent.
Graphite, molybdenum disulfide, copper powder, etc. are materials that resist wear.
Calcined kaolin is used as insulation.
Barrier: quartz, mica, montmorillonite, etc.
The additive is resin-specific.
Nucleating agents are effective for copolymerized polypropylene; red phosphorus flame retardants are effective for PA, PBT, and PET; nitrogen-based flame retardants are effective for oxygen-containing species, including PA, PBT, PET, and others; and glass fiber heat-resistant modification is effective for crystallization. Amorphous plastic performs poorly compared to conductive plastic; crystalline resin performs well when carbon black is added to conductive plastic.
Different types of the same composition's additives have a significant impact on the modification.
1. The additive's form
It is good that fibrous additions have a strengthening impact. The aspect ratio is a measure of how fiberized an additive is; the higher the L/D, the stronger the reinforcing effect; for this reason, glass fiber is added through the vent hole. than retain the aspect ratio and lower the likelihood of fiber breakage, the molten state is preferable than the powder state.
The spherical additive has a high brightness and an excellent toughening effect. Due to the fact that barium sulfate is a characteristic spherical additive, it is used to fill high-gloss PP. It may also be used to increase small stiffness and toughening.
2. additives' particle size
A. The impact of additive particle size on mechanical characteristics
The filler material's tensile and impact strength benefit more from smaller particle sizes than larger ones.
B. The impact of additive particle size on flame retardant qualities
The effectiveness of a flame retardant increases with decreasing flame retardant particle size. For instance, less hydrated metal oxide and antimony trioxide must be used to have the same flame retardant effect as smaller particle sizes.
C. How additive particle size affects color matching
The higher the tinting strength, the stronger the concealing power, and the more uniform the color, the smaller the colorant's particle size. The colorant's particle size does not, however, go as small as it might; there is a limit, and the limit varies depending on the property. When it comes to tinting strength, azo colorants have a limit particle size of 0.1 m, whereas phthalocyanine colorants have a limit particle size of 0.05 m. The colorant's maximum particle size for concealing power is around 0.05 m.
D. The impact of additive particle size on electrical conductivity
Using carbon black as an example, the easier it is to create a network conductive channel, the less carbon black has to be added to have the same conductive effect. However, just like a colorant, a particle size has a limit value. If a particle size is too tiny, it is simple to collect and challenging to disperse, which has a negative effect.
3. Additive surface treatment
In order to ensure that the additive and the resin are dispersed according to the anticipated structure, to complete the design index, to ensure that the effect will be exerted for a long time within the service life, and to ensure that it is resistant to extraction, migration, and precipitation, the compatibility between the additive and the resin is better. For instance, the majority of formulations call for the uniform dispersion of additives and resins, and it is preferable for additives to be spread in layers inside the resin for barrier formulations. With the exception of a few additions, like surfactants, high compatibility with the resin is essential to maximize the addition's effectiveness.
As a result, it is essential to make an effort to increase or improve its compatibility, such as by using a coupling agent or compatibilizer for surface activation treatment.
The modifying impact will be enhanced following the treatment of the surfaces of all inorganic additives. The most visible ones are fillers, but there are also glass fibers and inorganic flame retardants.
Coupling agents and compatibilizers are the principal ingredients used in surface treatment. The coupling agents are specifically silanes, titanates, and aluminates. The resin's equivalent maleic anhydride-grafted polymer serves as the compatibilizer.