There are various molding methods for plastic film, mainly including extrusion molding (including extrusion blown film, extrusion cast film method, extrusion composite film method), solution cast molding, rolling molding, dry composite film method for secondary molding processing, mechanical processing method, etc.
Extrusion molding of thin films
The extrusion molding of thin films is a method of forming thin films mainly using extruders as the main molding equipment. It includes extrusion blown film method, extrusion cast film method, extrusion composite film method, etc. The extrusion blown film method is divided into flat blowing method, upward blowing method, downward blowing method, etc. according to the different methods of bubble blowing and cooling. The upward blowing method for extruding blown film is the most commonly used method for plastic film molding; The down blowing method for extruding blown film is the simplest production method for high transparency plastic film. The extrusion blown film method can produce single-layer and multi-layer films. If the process flow of double blowing of film bubbles is adopted, the extrusion blown film method can produce biaxially stretched films and heat shrinkable films. The film produced by extrusion blown film method is in the form of a simple or sheet-like film. The commonly used plastic materials for producing thin films by extrusion blown film method include LDPE, HDPE, LDPE, P, EVA, PVC, PA, BS, PVDC, etc.
Extrusion casting film method, also known as flat film method or “T” – shaped film method, is mainly used for producing single-layer or multi-layer sheet-like films. Extrusion casting film, after subsequent stretching process treatment, can produce unidirectional and bidirectional stretching films, breathable and impermeable films, and heat shrinkable films, which is the fastest developing film forming technology in recent years. The commonly used plastic materials for producing thin films by extrusion casting film method include LDPE, LDPE, EVA, PP, PET, PA, etc.
The extrusion composite film method is to directly coat the extruded hot melt film onto continuously transported sheet and film materials such as paper, fabric, and plastic film, and then cool and press them together to form a composite film. Extrusion composite film does not use solvents, and its extruded hot melt and substrate can be two different materials. The plastic materials used for producing composite films by extrusion composite method mainly include FE, PA, PET, EVA, ENOH, EM ionic polymers, etc.
