Troubleshooting guide for Extrusion Coating Applications
Extrusion Coating Troubleshooting
Problem
Probable Cause
Suggested Remedy
Temperature Setting
Temperature setting are crucial parameter for proper plastic processing ,hence one should check temperature controller, thermocouple and solid state relay(SSR)
- when you cold start the machine ,wait for 2hours.
Poor Adhesion
- Less polymer melt wetting on to the substrate
- Less chemical bonding
- Improper material combination
- Polymer melt cooled due to low chill roll temperature
- Void in polymer melt
- Increase temperature up to 300°C for LLDPE and 260°C for PP.Check the heater elements
- Increase the air gap between die and nip roll for better bonding or reduce line speed
- Use LLDPE blend % with PP for PP fabric coating or reduce LLDPE blend percentage for HDPE raffia fabric coating or improper grade selected.
- Reduce chill roll temperature
- Preheat to avoid moisture or avoid volatile content in the polymer
Pin Holes
1. Substrate roughness
2. low Coating Weights
- Smooth surface of fabric substrate
- Ensure uniform coating thickness
Surging
Bridging in Hopper and Screw
Selection of proper screw and L/D ratio required
Edge Tear
- Irregular flow of melt through die
- Excess draw down
- Set proper temperature and condition of the die ends
- Reduce line speed
Draw Resonance
- Flow irregularities in machine direction
- Polymer degradation
- Decrease the die gap or increase the coating thickness
- Set proper temperature profile
Gels and Oxidation
- Resin contamination
- Excessive degradation
- Use clean and proper material handling tray
- Lower melt temperature or increase the screw speed or check for localised hot spots or incompatible or fresh blends or poor dispersion of pigments, additives or unmelted pellets
Rough Waxy Appearance
- Improper material mixing
- Poor purging
- Polymer degradation
- Select similar rheology blend
- Purge thoroughly
- Set proper temperature profile
Breaks / Molten Curtain
Draw down too low or too high
Set proper line speed
Neck-in
Irregular flow across die
• Reduce line speed
• Reduce melt temperature
• Select high MFI or low density material
