Plastic recycling has become an important part of the global plastics industry. Recycling helps reduce plastic waste and lowers raw material costs for manufacturers. However, compared with processing virgin plastic, recycling plastics often causes much faster wear of the screw and barrel in extrusion and pelletizing machines.
Understanding why screw and barrel wear occurs in plastic recycling can help manufacturers choose the right materials, improve equipment lifespan, and reduce maintenance costs.
Below are the main reasons why screw and barrel wear quickly in plastic recycling.
1. Presence of Abrasive Contaminants
Recycled plastic materials often contain various contaminants and impurities, such as:
- Sand and dust
- Metal particles
- Glass fragments
- Mineral fillers
These abrasive particles act like sandpaper inside the barrel. When the screw rotates at high speed, these particles continuously rub against the screw flights and barrel inner surface, causing rapid wear.
Over time, the clearance between the screw and barrel increases, reducing processing efficiency.
2. High Content of Fillers
Many recycled plastics contain high levels of fillers, such as:
- Calcium carbonate (CaCO₃)
- Talc
- Glass fiber
These materials are much harder than standard plastics and significantly increase abrasion inside the extrusion system. The constant friction between these fillers and the metal surfaces accelerates wear of both the screw and barrel.
In such conditions, standard nitrided barrels may wear out much faster.
3. Mixed Plastic Materials
Unlike virgin materials, recycled plastics often consist of mixed polymer types, such as:
- PE mixed with PP
- Contaminated film waste
- Multi-layer plastic materials
Different plastics melt at different temperatures and have different viscosities. This inconsistency can cause unstable melting and uneven pressure inside the barrel, which increases mechanical stress on the screw and barrel surfaces.
4. Higher Processing Temperatures
Recycled materials often require higher processing temperatures to achieve proper melting and mixing. Higher temperatures can accelerate:
- Material degradation
- Corrosion of metal surfaces
- Wear of screw flights
Prolonged operation under high temperature conditions can significantly shorten the lifespan of standard screw barrels.
5. Poor Material Cleaning
In some recycling operations, plastic waste may not be thoroughly washed before processing. Residual contaminants such as:
- Dirt
- Paper
- Aluminum fragments
- Labels or adhesives
can damage the screw and barrel during extrusion.
Even small amounts of metal particles can cause serious scratching or scoring inside the barrel.
6. High Mechanical Load
Recycling processes, especially plastic pelletizing and film recycling, often involve high torque and heavy mechanical loads. The screw must work harder to compress and mix contaminated materials.
This heavy load increases friction and stress between the screw and barrel, accelerating wear.
7. Inadequate Material Selection for Screw Barrel
If the screw and barrel are made from standard nitrided steel, they may not be suitable for harsh recycling environments.
For recycling applications, it is often recommended to use:
- Bimetallic barrels with tungsten carbide alloy
- Wear-resistant screw coatings
- Chrome-plated screws
These materials significantly improve resistance to abrasion and corrosion.
Conclusion
Plastic recycling is a demanding process that exposes the screw and barrel to high levels of abrasion, contamination, and mechanical stress. As a result, screw and barrel wear occurs much faster compared with processing virgin materials.
By understanding the causes of wear and choosing wear-resistant screw barrel solutions, manufacturers can extend equipment lifespan and improve production efficiency.
Zhoushan Juyuan Machinery Co., Ltd. specializes in manufacturing high-quality screw barrels for plastic recycling, extrusion, and injection molding machines. We offer durable solutions designed for abrasive recycled materials.
Website: https://juyuan-machinery.com/
Email: cxj.job@gmail.com
WhatsApp / WeChat: +86 13905808474