How to choose the right additives for plastic modification

The plastic formula design looks very simple, but often simple things are not easy to pay attention to, which affects the final result. So, how to design a high-performance, easy-to-process, and low-cost formula?
01

Think clearly about the performance you want, and then choose the corresponding additives

（1）Toughening
Choose elastomers, thermoplastic elastomers and rigid and toughened materials;
（2）Enhance
Choose glass fiber, carbon fiber, whisker and organic fiber;
（3）Flame retardant
Bromine (common bromine and environmentally friendly bromine), phosphorus, nitrogen, nitrogen/phosphorus composite intumescent flame retardant, antimony trioxide, hydrated metal hydroxide;
（4）Antistatic
Various antistatic agents;
（5）Conductive
Carbon (carbon black, graphite, carbon fiber, carbon nanotube), metal fiber and metal powder, metal oxide;
（6）magnetic
Ferrite magnetic powder and rare earth magnetic powder include samarium cobalt (SmCo5 or Sm2Co17), neodymium iron boron (NdFeB), samarium iron nitrogen (SmFeN), aluminum nickel;
（7）Heat conduction
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;
（8）Heat resistant
Glass fibers, inorganic fillers, heat-resistant agents such as substituted maleimides and β crystal nucleating agents;
（9）transparent
Nucleating agent, α-crystal nucleating agent sorbitol series has the best effect for PP;
（10）Wearable
Graphite, molybdenum disulfide, copper powder and other three types of cobalt magnetic powder;
（11）insulation
High-alumina calcined
（12）cut off
Mica, montmorillonite, quartz, etc.
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02

Not only is the resin picker, but the adjuvant is also “picky” on the resin!

The additives of the same composition have different forms, which have a great influence on the modification effect.
(1) Red phosphorus flame retardant is effective for PA, PBT and PET;
(2) Nitrogen-based flame retardants are effective for oxygen-containing products, such as PA, PBT, PET, etc.;
(3) The nucleating agent has a good effect on the copolymer polypropylene;
(4) The heat-resistant modification of glass fiber has a good effect on crystalline plastics, but a poor effect on amorphous plastics;
(5) Carbon black is filled with conductive plastic, which has good effect in crystalline resin.
03

Different forms of additives may have very different effects!

（1）Fibrous additives have good reinforcing effect：
The degree of fiberization of the additives can be expressed by the aspect ratio. The larger the L/D, the better the reinforcement effect. This is why we add glass fiber through the vent hole.
（2）The molten state is better than the powder state to maintain the aspect ratio and reduce the probability of fiber breakage;
（3）The spherical additives have good toughening effect and high brightness：
Barium sulfate is a typical spherical additive, so barium sulfate is used for filling high-gloss PP, which is rigid and toughened in a small range.
04

The particle size of the additives is also very particular!

(1) The effect of particle size of additives on mechanical properties:
The smaller the particle size, the more beneficial it is to the tensile strength and impact strength of the filler;
(2) The effect of particle size of additives on flame retardant performance:
The smaller the particle size of the flame retardant, the better the flame retardant effect. For example, the smaller the particle size of hydrated metal oxide and antimony trioxide, the smaller the amount of addition to achieve the same flame retardant effect;
(3) The effect of particle size of additives on color matching:
The smaller the particle size of the colorant, the higher the tinting power, the stronger the hiding power, and the more uniform the color;
(4) The influence of the particle size of the additives on the electrical conductivity:
Taking carbon black as an example, the smaller the particle size, the easier it is to form a network-shaped conductive path, and the amount of carbon black added to achieve the same conductive effect is reduced. But like the colorant, 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.

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