Multilayer films are essentially produced by two main manufacturing methods: film lamination and film co-extrusion. In some cases, it is possible to combine the two methods to produce certain more complex multilayer films. In other cases, additional methods, such as coating, printing, vacuum plating, etc., may be used as a method of producing the finished product. In this way, there are many production methods and collections of production methods to make many of the multilayer films available on the market.
The main advantages of co-extrusion over lamination are: there is no cost of equipment for the production of films for lamination, there are no film handling costs or problems, there are fewer cosmetic and adhesion problems, it is possible to use polymers in non-film form (including thinner film layers), there is sufficient compatibility of the different structural layers for co-extrusion from an economic point of view and the production batch sizes are sufficiently large to justify the cost-effectiveness of co-extruding for the production of such products. Co-extrusion is certainly the preferred method for the production of such multilayer products when it is cost-effective to produce such products. Important to successful co-extrusion is that the equipment, polymers and operating conditions designed for the technology of the desired film structure have been adequately developed so that a first class film product can be co-extruded.
1. Single-layer cast film extrusion
Before we look at co-extrusion, we should explain a little about single-layer cast film and sheet. The difference between sheet and film is not conclusive, but film is generally regarded as being less than 250 µm thick. extrusion equipment for cast film and sheet is very similar. There are often differences in the range of roller sets. The cast film system is most commonly extruded from the die head to the cast rollers vertically down to a series of horizontal rollers, this geometric arrangement avoids excessive sagging of the film between the die head and the gap between the series of rollers, which can occur if the film is extruded using a shuping die head exit. 2.
2. Single layer blown film extrusion
Blown film extrusion systems can use the same extruders (same design and screws) as flat die head systems. The difference between the two is the die head, which for blown film is a round nose die head. These die heads are available in sizes ranging from 10 to 200 μm, and air is blown through the extruded tubular die in the die head machine and into a film bubble. The larger the ratio of the bubble diameters (called the blow-up ratio), the thinner the film is blown. After sufficient cooling, an ejection system flattens the film bubble. Controlled and pressurised air from the die head blows the bubble to a controlled size.
Nanjing Suminoe Precision Machinery Co., Ltd. has professional cast film production line, the company's main cast film manufacturing line: TPU hot melt adhesive film production line, CPP/CPE cast film production line, EVA solar encapsulation adhesive film production line, PE sanitary breathable film production line, PVDF cast film production line, PP 3D film production line, medical blood purification film production line, multilayer co-extruded barrier film production line, LLDPE winding film production line, LLDPE film production line, LLDPE film production line, LLDPE film production line, LLDPE film production line, LLDPE film production line. production line, LLDPE winding film production line and so on.
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