Plastic film extrusion is a plastic forming process. The type of extrusion largely determines the optical properties of the resulting material. Below we describe the system and its applications in detail.
What is plastic co-extrusion and what is it used for?
In the packaging production process, plastic extrusion consists of guiding thermoplastic material under pressure through a die with a hole that is generally complex in shape. The resulting cross-section of the material is the same shape as the hole.
The co-extrusion of plastic film is synonymous with multilayer extrusion, meaning polymers with different properties can be combined. In short, co-extrusion consists of the simultaneous extrusion of more than one polymer through a die to form a multi-layer structure. This system evenly distributes the co-extruded material to guarantee an even thickness.
It is a complex process during which the polymer is melted in a cylinder and then cooled in calender rolls.
The process means resin consumption can be optimised by combining recycled materials, and the use of multiple sheets of film results in multi-layer packaging with better barrier properties and the possibility of protective atmospheres (MAP).
Blown and cast film production
Two systems are used to produce co-extruded plastic films: blown film co-extrusion and cast film co-extrusion.
Blown film co-extrusion
The blown-film co-extrusion process affords the option of a wide variety of layers and very versatile packaging. It combines properties of different polymers to obtain a product with the properties of each of its component materials, including reduced thickness and lower cost.
If the polymers in the different layers of the film are physically compatible, there is no need to use substances between them to act as an adhesive, as they should stick together naturally. Moreover, if these materials have similar extrusion conditions, there will be fewer problems in the die designs.
SP GROUP boasts two ample categories of flexible packaging and special flexible films that are produced through the blown-film process. They include:
- SOL: This is our star product. A co-extrusion of special flexible film, it has a reduced thickness and many properties. It is principally used in a complex with polyester as a top film for trays containing food products such as pre-packaged sliced meats and cheeses.
- SOL EFFICIENT: Within the SOL range, SOL EFFICIENT is a co-extrusion with a high barrier to oxygen and water vapour, and which is suitable for MAP. It is efficient because it welds to PET trays, improving their recyclability.
Cast film co-extrusion
The cast film co-extrusion process is quite different to the blown film process. It is used to obtain thermoformed products (such as packets, blister packs and disposable items) and films of different thicknesses for different uses.
This process is highly productive with better cooling and optimal control over the sizes and properties of the final product.
Some of the materials produced using the cast co-extrusion system are:
- APET PE: The thickness of this material is ideal for thermoforming base webs. It provides something of a barrier so it can be used for MAP. It has good transparency, but can also be made in any colour. It is frequently used for meat, fresh fish and sliced cheese, as well as having many other uses, including different formats for non-food products.
- RST BASE WEB: This is a semi-rigid co-extrusion that is puncture resistant, sterilisable and has a good gas and water vapour barrier. It is also microwaveable. Its most frequent applications include packaging for pulses and meats, as well as products such as vacuum-packed beetroot and corn cobs.
Did you find this information interesting? SP GROUP has an extensive catalogue of co-extruded products that enhance the properties of packaging to ensure the safest, most resistant and most innovative solutions for your needs.
Visit our website to discover everything we have to offer.