Cast Film Chill Roll Cooling Calculator
Polymer film extrusion & optical clarity: Calculate chill roll heat transfer, web residence time, quench cooling rate (dT/dt), and crystallization pinning temperature.
Line Speed & Film Web Geometry
Thermal Quench & Crystallization
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
Why is a high cooling rate critical for cast polypropylene (CPP) optical clarity?
Semi-crystalline polymers like polypropylene naturally form large crystalline spheres (spherulites) that scatter visible light, causing haziness. Rapid quenching on a cold chill roll (>500°C/s) freezes the molecular chains into fine, micro-crystalline domains smaller than the wavelength of light, yielding glass-like optical clarity and high gloss.
What is web "pinning" and why is it essential on a cast film line?
As extruded melt hits the spinning chill roll, a boundary layer of air is dragged beneath the web, creating an insulating air cushion that prevents direct thermal contact and causes blotchy cooling defects. Pinning devices (air knives, vacuum boxes, or high-voltage electrostatic wires) force the molten film firmly against the chrome roll, dramatically increasing heat transfer.
How does line speed affect chill roll diameter selection?
As line speeds increase to 400–600 m/min, the web residence time over the roll drops to tens of milliseconds. To ensure the film solidifies below its glass transition or crystallization point before takeoff, engineers must install larger chill roll diameters (up to 1,000–1,200 mm) to increase contact wrap length.