EXTRUSION COATING TROUBLESHOOTING GUIDE

Download Printable Version pdf

Problem Possible causes Possible solution
  Adhesion Low melt temperature Increase the melt temperature to help oxidise the surface and prevent premature cooling
 Increase back pressure in the extruder
 Air gap too low Increase the air gap to get adequate oxidation of the surface
 Line speed too high Decrease the line speed to allow additional time in the air gap for oxidation of the surface
 Substrate surface untreated Pre-treat substrate (such as corona treatment, flame treatment and ozonation) or add a chemical primer to improve wettability
 Pre-treatment ineffective Inspect treatment method, adjust treatment settings as required, ensure primer coverage is adequate and drying time is sufficient
 Sticking to chill roll Decrease the chill roll temperature
 Low nip roll pressure Increase the pressure of nip rolls, ensure pressure is evenly distributed
 Air gap too high Decrease the air gap to avoid premature cooling
 Low chill roll temperature Increase the temperature of the chill roll to help overcome quick cooling
 High melt temperature Decrease the melt temperature to avoid thermal degradation, decrease back pressure in extruder
 Surface active additives (e.g. slip) Modify the additive package
 Inadequate resin selection Ensure resin is compatible with substrate, lower viscosity (high melt index) resins adhere better to porous substrates
  Apple sauce High melt temperature Decrease the melt temperature
 Inadequate mixing or poor melt quality Increase the back pressure of the extruder and use finer screen packs
 Interfacial instability in coextrusion Check flow properties of resins
 Contamination Ensure adequate purging time and cleaning of transfer lines
 Check resin for any foreign material
  Die Lip Build-Up Additives Modify the additive package
 High melt temperature Decrease the melt temperature to avoid thermal degradation
 Melt scraping against die lip Machine the die lip
 Change angle at which the melt contacts the chill roll
 Excessive resin shear Lower output
 Increase the die lip temperature
 Increase the die gap
  Draw Resonance High draw ratio Decrease the die gap
 Increase the coating weight
 High melt temperature Decrease the melt temperature
 Melt strength of polymer is too low Select higher melt strength resin
  Edge Tear High draw ratio Decrease the die gap
 Increase the coating weight
 Low melt temperature Increase the melt temperature
 Incorrect deckle settings Decrease the off-set between internal deckle settings
 Inadequate die design Seek advice from manufacturer
 Melt strength of polymer is too high Select lower melt strength resin
 Splicing Reverse splice direction, seek advice from machine manufacturer
 Melt index too low for coating weight Use higher melt index resin
  Gauge bands High melt temperature Decrease the melt temperature to increase melt viscosity
 Dirty die Clean the die to remove any build-up of material
 Variation in temperature control Check the temperature zones are running correctly and use flat temperature profile
 Inadequate die set-up Adjust the die bolts accordingly
 Poor melt quality Increase the back pressure of the extruder and use finer screen packs
  Gels and voids Moisture Check raw materials for moisture (e.g. resin and substrate)
 Ensure storage conditions are dry
 Degradation of polymer Decrease the melt temperature
 Check temperature zones are running correctly
 Contamination Ensure adequate purging time and cleaning of transfer lines
 Check resin for any foreign material
 Inadequate mixing Increase the back pressure of the extruder and use finer screen packs
 Dirty die Clean the die to remove any build-up of material
  Neck-in High melt temperatures Decrease the melt temperature
 High draw ratio Decrease the air gap
 Increase the coating weight
 Melt strength of polymer is too low Select higher melt strength resin
  Odour / Taint High melt temperature Decrease the melt temperature to reduce thermal degradation
 Air gap too high Decrease the air gap to reduce the time for oxidation of the surface
 Additives Modify the additive package
  Pinholes Substrate roughness Use flame treatment on the substrate
 High melt temperature Decrease the melt temperature
 Low coating weight Increase the coating weight
 Dirty or damaged idler rollers Inspect and clean the idler rollers or replace if necessary
 Excessive tension Decrease the tension accordingly
  Sealability High melt temperature Decrease the melt temperature to reduce thermal degradation
 Air gap too high Decrease the air gap to reduce the time for oxidation of the surface
 Additives (e.g. slip) Modify the additive package as some additives may bloom to the surface and contaminate the seal
 Inadequate sealing conditions Increase the sealing temperature or dwell time
 Contamination Clean the chill roll surface and limit handling of coating surface
 Inadequate resin selection Use higher melt index resin
 Excessive corona treatment Check treatment level and adjust if necessary
  Surging Inadequate screw design Seek advice from manufacturer, increase back pressure in extruder
 Inconsistent hopper feeding Decrease the temperature at the feed zone to stop bridging

The information contained in these guidelines is provided in good faith and may assist with problem solving and troubleshooting.

The information is offered solely for your information and is not all-inclusive – other variables or constraints may impact the ability of the user to apply them. The user should conduct its own investigations and satisfy itself as to whether the information is relevant to the user’s requirements. The user should not rely upon the information in any way. The information shall not be construed as representations of any outcome for which Qenos assumes any legal liability. Qenos expressly disclaims liability for any loss, damage, or injury directly or indirectly suffered or incurred as a result of or related to anyone using or relying on any of the information. There is no endorsement of any product or process, and Qenos expressly disclaim any contrary implication.

Products & Services