How to improve the scratch resistance and wear resistance of plastics

1.Choose the appropriate matrix resin

Usually, ultra-high molecular weight polyethylene (PE-UHWM) is one of the most wear-resistant plastics, and choosing PE-U · HWM can easily improve the material's wear resistance. In addition, plastics with high crystallinity and regularity are more wear-resistant, while plastics with high hardness are more wear-resistant. Plastics composed of macromolecules such as benzene rings, such as polystyrene, are not wear-resistant. In the modification of polypropylene (PP), polyolefin elastomers (POE), ethylene propylene diene monomer (EPDM), and thermoplastic dynamic vulcanized rubber (TPV) (such as dynamic vulcanized PP/EPDM) are usually used to toughen PP, and the addition of elastomers generally leads to a decrease in scratch resistance. Therefore, it is very important to choose a suitable elastomer, and the comparison order of scratch resistance is as follows: TPV>EPDM>POE.

2. Use fillers with good wear resistance

(1) Molybdenum disulfide.

Molybdenum disulfide is a wear-resistant additive mainly used in nylon plastics. Molybdenum disulfide acts as a crystallization agent to increase the crystallinity of nylon and produce a harder and more wear-resistant surface for the nylon material. Molybdenum disulfide has a high affinity for metals. Once adsorbed on the metal surface, the molecules of molybdenum disulfide will fill the pores visible only under a microscope, making the metal surface smoother. This makes molybdenum disulfide an ideal wear-resistant additive for nylon and metal friction situations.

(2) Graphite.

The structure of graphite is the crystal structure of mineral graphite, which is a hexagonal layered structure. This unique chemical structure allows graphite molecules to easily slide against each other when subjected to very little friction. This wear-resistant property is particularly important in environments with water. Therefore, graphite is an ideal wear-resistant additive used in many products placed in water, such as water lined shells, impeller blades, and seals.

(3) Glass fiber.

Glass fiber can form a strong mechanical bond between polymers, so it can improve the integrity of thermoplastic structures and improve wear resistance. Glass fiber provides reinforcement and can improve the thermal conductivity and deformation of plastics, significantly improving their load resistance and wear resistance.

(4) Carbon fiber.

Similar to glass fiber, carbon fiber can significantly improve the overall structure, load resistance, and wear resistance of materials. Unlike glass fiber, carbon fiber is a softer and less abrasive fiber that does not scratch the iron or steel friction surface it rubs against.

(5) Aromatic polyamide fibers.

Aromatic polyamide fiber is also one of the wear-resistant additives. Unlike glass fiber and carbon fiber, it is the softest and most scratch free fiber, which is the main advantage of aromatic polyamide fiber in wear-resistant applications.

3. Add appropriate wear-resistant additives

(1) Polytetrafluoroethylene (PTFE).

The friction coefficient of polytetrafluoroethylene (PTFE) is very low, and during the friction process, PTFE molecules will form a lubricating film on the surface of the part. PTFE has excellent lubrication and wear resistance under friction, and is the best wear additive in high load applications. These high load applications include hydraulic piston ring seals and thrust washers. The PTFE content is generally 15% in non crystalline plastics and 20% in crystalline plastics.

(2) Polysiloxane.

Polysiloxane liquid is a migratory wear-resistant additive that, when added to thermoplastic plastics, slowly migrates to the surface of the part and forms a continuous thin film. The lower the viscosity of polysiloxane, the faster it can migrate to the surface of the part to provide wear resistance. However, the viscosity of polysiloxane should not be too low, as it is prone to volatilization and will quickly disappear from the part.

(3) Smoothing agent.

When lubricating agents such as oleic acid amide and erucic acid amide are added to thermoplastic plastics, they migrate to the surface of the workpiece to create a wax layer, reducing the friction coefficient while also reducing the visibility of scratches. The disadvantage is that they cannot completely improve the surface adhesion phenomenon.

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