The “Longevity” Secret of Barrels And Screws: How To Resist The Deadly Damage of Corrosive And High-Temperature Resins

In the plastic processing industry, the barrel and screw are core components of extrusion and injection molding equipment. However, they face two major "enemies": corrosive resins and high-temperature wear. Whether it's hydrochloric acid released by PVC or hydrofluoric acid from fluoropolymers, these chemicals can cause severe damage to metal components. Additionally, thermal expansion mismatches during high-temperature resin processing can lead to seizure issues, threatening both equipment lifespan and production efficiency.

So, how can we extend the service life of barrels and screws and protect them from this “deadly damage”? This article explores corrosion resistance, high-temperature durability, anti-wear technologies, and practical maintenance tips.

1. The Threat of Corrosive Resins: The Hidden Killer

Corrosive resins like PVC, acetal, and fluoropolymers release acidic by-products during processing:

PVC: Releases hydrochloric acid, corroding metal surfaces.

Acetal resin: Produces formic acid, which erodes the barrel and screw.

Fluoropolymers: Emit hydrofluoric acid, causing rapid corrosion of standard steel.

Root Cause:

Standard barrels and screws made of nitrided steel, tool steel, or alloy steel are vulnerable to acid attack and can deteriorate rapidly under these conditions.

2. The Thermal Expansion Crisis: The Root of Seizing Problems

During high-temperature resin processing, such as with fluoropolymers, mismatches in the coefficient of thermal expansion (CTE) between barrel and screw can cause seizing:

Gap variation: Different CTEs lead to shrinking or expanding gaps.

Thread damage: Too small a gap causes direct metal contact, leading to thread wear or breakage.

Productivity loss: Seizing accelerates wear, increases downtime, and reduces efficiency.

Solutions:

Material matching: Use materials with similar CTEs for both components.

Precision gap control: Maintain screw-barrel clearance around 1/1000 of the diameter. Rebuild or repair if clearance exceeds limits.

3. Triple Protection: Corrosion Resistance, Heat Resistance, and Wear Resistance

a. Corrosion Resistance

Bimetallic barrel linings: Nickel-rich boron alloy liners with molybdenum, boride, and carbide bases offer excellent acid resistance.

Surface hardening: Apply Colmonoy 56 or Colmonoy 83 alloy coatings on screws for light corrosion and wear protection.

b. High-Temperature Design

Low-CTE materials: Choose corrosion-resistant metals with low thermal expansion to reduce thermal mismatch.

Hot isostatic pressed barrels: Suitable for injection and extrusion with high-temp resins, improving longevity.

c. Wear Resistance

Tungsten alloy coatings: Applied on screw surfaces and barrel liners for superior abrasion resistance.

Medium-carbon treated steel: Used as a screw base with hardened weld overlays to enhance durability.

4. Maintenance Tips: Routine Checks for Extended Equipment Life

a. Regular PM Inspections

Check barrel-screw clearance regularly (target: 1/1000 of diameter).

Repair worn parts promptly to avoid major damage.

b. Repair Over Replacement

Opt for repairing rather than fully replacing worn screws/barrels to reduce cost.

Damaged barrel liners in injection molding machines can be replaced to restore function.

c. Prevent Melt Backflow

Wear at any point on the screw can cause melt backflow, accelerating damage. Regular checks can prevent this.

5. Case Study: Saving a Corroded Screw

Problem:

A plastic factory processing fluoropolymers experienced severe screw corrosion, leading to low efficiency.

Solution:

Replaced standard barrel with a bimetallic liner for enhanced corrosion resistance.

Applied Colmonoy 83 hardening to the screw surface.

Established routine clearance checks between barrel and screw.

Results:

Equipment lifespan increased by 30%.

Production efficiency improved by 20%.

Annual maintenance costs reduced by CNY 150,000.

6. Conclusion: Key Factors for Long-Lasting Barrels and Screws

Material Selection: Use corrosion-resistant, heat-resistant, and wear-resistant materials.

Design Matching: Match thermal expansion properties of barrels and screws to avoid seizing.

Regular Maintenance: Perform PM checks and repairs to extend service life.

By following these practices, barrels and screws can withstand the “deadly damage” of corrosive and high-temp resins, ensuring long-term performance and adding significant value to plastic processing operations.

NANJING HAISI is professional manufacturer of screw barrel of extruder, we supply Twin Screw Extrusion Line, Single Screw Extrusion Line, Plastic Recycling Extrusion Line, Two Stage Extrusion Line, Lab Scale Extrusion Line, Mixing and Feeding Machine, Cooling and Pelletizing Machine, Crushing Machine and so on.