HERC silicone coating for cast extrusion lines
The silicone-coated rollers in the extruder area of cast film extrusion lines play a fundamental role. Unlike the main chill roll (which is made of chrome-plated steel and internally cooled), the silicone-coated rollers operate in direct contact with the molten or semi-molten polymer at high temperatures.
Their main application in this specific area is the nip roller of the cooling calender or the first return and drive rollers and our “HERC” (High Elastic Return Coating) Silicone, a high elastic return silicone coating is the right answer to improve the process performances
Main Functions in the cast extruder area
- Non-stick properties (Release): The silicone prevents the molten plastic resin (PP, PE, PET, etc.) just exiting the extruder head from sticking to the surface of the pressure roller.
- High thermal resistance: Working close to the flat die, silicone compounds guarantee structural stability and maintain elasticity at continuous high temperatures (generally up to 200°C, with special peaks up to 300°C).
- Homogeneous pressure: The elasticity of the silicone rubber allows uniform pressure to be exerted on the film against the chill roll, eliminating trapped air bubbles and improving thermal shock and the flatness of the film.
Typical Technical Specifications for Cast Extrusion
Depending on the specific application of the cast line, rubber cylinders differ in some crucial characteristics of the compounds:
- Hardness (Shore A): Softer compounds (50-60 ShA) for greater footprint; harder compounds (70-80+ ShA ) for greater mechanical resistance.
- Surface finish: It can vary from smooth to slightly matt or embossed depending on the aesthetic/functional effect required on the plastic film.
A.Piovan , specializing in converting and extrusion, supplies silicone coatings with high elastic recovery formulations: they maintain constant pressure and contact on the film, cycle after cycle, without losing geometry, to optimize the life of the roller and reduce machine downtime.
