Reinforcers for nylon and their characteristics

Reinforcers used to stiffen nylon are roughly classified as follows.

Nylon is a polar crystalline polymer, not all elastomers are suitable for stiffening nylon. Generally speaking, polar elastomers are more suitable for increasing strength of nylon. Of course, introduction of polar groups into macromolecular chains of non-polar elastomers by graft copolymerization can also be used to improve toughness of nylon.

1. Rubber elastic case. Rubber elastomers are ideal reinforcing polymers. The main reason is that rubber has a high modulus of elasticity and a low glass transition temperature, which can give plastics excellent resistance to low temperature brittleness. EPDM rubber, ethylene propylene rubber, nitrile rubber, styrene butadiene rubber, butadiene rubber, etc. are used as reinforcing material of nylon. EPDM is most commonly used.

Rubber is used as a reinforcing agent for nylon. It is best to vulcanize before use, that is, make rubber moderately cross-linked, so that it changes from a linear structure to a mesh structure, so that it has a certain strength and hardness. Reinforced nylon to achieve desired stiffening effect.

2. Thermoplastic elastomer. The difference between thermoplastic elastomer and rubber is that it can be used directly for stiffening without vulcanization and crosslinking. Its elasticity is close to that of rubber. Thermoplastic elastomers are copolymerized polymers or graft copolymers.

SBS (styrene/butadiene copolymer) has high elasticity due to presence of butadiene in macromolecule, and elasticity of SBS will be different with different butadiene content.

SEBS is a hydrogenated product of SBS. The biggest feature of this product is that it is more weather resistant than SBS.

All of above are copolymers of monomers to form thermoplastic elastomers. In addition, thermoplastic elastomer obtained by mixing reaction twin screw extrusion with rubber as main body, mixed with some plastics, under action of a crosslinking agent, can also be used as a reinforcing material, such as EPDM/PP, EPDM/PE, etc. .

The characteristics of nylon reinforced with thermoplastic elastomer differ from those of nylon reinforced with rubber. The flexural strength of thermoplastic elastomer-reinforced nylon is higher than that of rubber-reinforced nylon.

3. Rigid organic polymers. There is far less research into strengthening hard organic particles than research into elastomers. There are not many types of organic rigid polymers that can enhance strength of nylon, such as liquid crystal polymers. But, based on principle of strengthening, polymers with a glass transition temperature lower than that of nylon have a certain strengthening effect.not on nylon, such as PP, PE, ABS, etc. However, these polymers are not as strong as elastomers.

4. inorganic rigid materials. This type of material is actually an inorganic filler, and when particle size of inorganic filler reaches nanometer size, it has a certain strengthening effect. Such as CaCO3, talc, montmorillonite, wollastonite, etc.

Hard particles have a certain reinforcing effect on nylon and can increase stiffness of nylon, but it is much less than reinforcing effect of elastomers. To obtain hardened nylon with good toughness and high rigidity, a composite reinforcing agent or a composite impact and strengthening technology can be used.

In addition, mustache also has a certain strengthening effect on nylon.

5. Metallocene polyolefins. Related to thermoplastic elastomers, such as ethylene-octene copolymer (POE), has excellent elasticity, and since there are no double bonds in macromolecular chain, it has good weather resistance. Initially, POE was mainly used to stiffen polyolefins, but POE has good compatibility with nylon after being grafted with reactive monomers such as maleic anhydride. Reinforced POE PA6 not only has high impact strength at room temperature, but also excellent impact resistance at low temperatures (-40°C), making it most suitable hardening agent for PA6 and PA66.

6. Core-shell copolymer. The so-called core-shell copolymer is a copolymer with a flexible molecule as core and a rigid molecule as shell structure. This copolymer has a strong reinforcing effect on nylon.