Troubleshooting guide for Cast PP Film Applications
Cast PP Films 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.
Irregular thickness profile of film
- Processing parameters
- Resin properties
- Check and adjust die gap to get uniform clearance, check and adjust the cast roll for stable and balanced rotation, adjust and balance the melt flow rate of skin and core layers, avoid excessive neck-in
- Use resin with narrower molecular weight distribution
Too big neck-in
- Processing parameters
- Resin properties
- Reduce extrusion temperature, adjust melt flow rate and cast roll speed
- Use resin with narrower molecular weight distribution, use resin with lower isotacticity
Plate-out
Due to insufficient film contact with chill roll
Adjust air-knife
Poor stiffness
Processing parameters
- Reduce extrusion temperature, increase cooling roll temperature, increase stretch
- Add nucleating agent in the additive formulation
Poor tear strength in the machine direction
Processing parameters
- Reduce chill roll temperature, reduce stretch
- Use resin with lower MFI and broader MWD
Friction coefficient too low
Processing parameters
Increase melt temperature, reduce chill roll temperature, reduce film thickness, the level of slip agent, increase the level of anti-blocking agents
Friction coefficient too high
Processing parameters
Reduce melt temperature, raise chill roll temperature, increase the level of slip agent, decrease the level of anti-blocking agents
Blocking
Processing parameters
Increase the temperature of cooling rolls, lower the processing temperature, lengthen the aging time, increase the level of anti-blocking agents, reduce the winding tension
Transparent spots
Processing parameters
- Increase the temperature of feeding and compression zone of extruder, take measures to improve mixing efficiency in the extruder, clean the melt distributor, increase back pressure
- Use resin with narrower MWD
Flow marks
Melt temperature too low
Adjust melt temperature, check temperature controllers for its functioning and accuracy
Brittle seals
Melt temperature too high
Adjust melt temperature, check temperature controllers for its functioning and accuracy
Haze/Poor clarity (Variable optical properties across the width)
- Processing parameters
- Coolent supply inadequate due to inlet water temperature and/or blocking of cooling circuits
- Reduce cooling roll temperature, raise processing temperature, increase air pressure in the air-knife chamber, decrease line speed.Take measures to improve the dispersion of anti-blocking agents, add nucleating agent
- Check cooling water line and adjust flow rate
Small bubbles or voids
Moisture and air entrapment in the resin, poor venting at extruder, master batch chemicals are not stable at extrusion temperature and forming volatiles
Change resin, increase transition zone temperature, increase back pressure, use high temperature stability master batch
Depression and pock marks
- Chilling/casting roll too cold
- Film thickness variation across its width
- Winding tension too high
- Adjust chilling roll temperature, increase melt temperature
- Adjust film thickness
- Adjust winding tension considering post winding shrinkage of film in the roll form
Stretch marks and corrugations
Insufficient cooling of film before winding
Cool the film to the ambient temperature before winding on the roll to avoid excessive stretching
