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Polypropylene (PP) in Packaging
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Similar to the way a 3D printer works, co-extrusion is all about melting and reforming plastics. There are a number of different extrusion methods, but all work under generally the same principle. Here is a look at the way extrusion works and what makes co-extrusion unique.
The Basic Extrusion Process
In the extrusion process, a machine with a hopper collects plastic beads or pellets that are melded together into one product. Any additional coloring or protective substances that need to be included in the finished product are then added. From the hopper, the plastic is funneled into a temperature-controlled chamber or tube. This tube heats the plastic to the point of melting.
After the plastic is sufficiently melted, it may go through a variety of different molding processes. Plastic bags, plastic insulated wires, and PVC pipes are all created using an extrusion method. Common extrusion methods include:
- Sheet extrusion. Taking a large sheet of thick plastic and running it through a die to change the consistency of the sheet. After the sheet has been reformed and is ready to be turned into packaging, it is thermoformed or heated and molded into a specific shape.
- Blown film. Plastic bags are created using this method. Once the melted material meets the die in this process, it is directed around an open space or spaces in the middle. From there, the material is cooled and the plastic is stretched with air pressure and rollers. During this process, the plastic becomes quite thin before cooling completely.
- Tubing extrusion. Similar to the way in which a blown film extrusion process takes place, tubing extrusion creates thicker, denser plastics that are hollow in the middle. Pipes and other hardware are commonly made using this method.
Co-extrusion
Co-extrusion is defined by the number of plastic substances or polymers used in the extrusion process. The substances are heated separately and then joined together before being molded into the proper shape. Because some plastics aren’t as strong, durable, or weatherproof as others, using a combination of materials is the best way to meet the needs of a product specification. Common plastic bases include:
- PET. Polyethylene terephthalate is an environmentally friendly, durable plastic substance used in many food and drink packages.
- HIPS. High-impact polystyrene is a polymer that is commonly used in prototypes and toys. It is a hard plastic that can withstand a high amount of force without breaking or splintering.
- PETG. Polyethylene terephthalate glycol is a slightly modified PET product that is good for blister packs and other packaging needs.
- HDPE. High-density polyethylene is made from petroleum and is used in 3D printing projects, bottle caps and hard hats.
- ABS. Acrylonitrile butadiene styrene is a mixed polymer used in some medical devices, watercraft and toys like Legos.
By combining plastics bases with different properties, packaging companies can create highly durable and effective packaging solutions for numerous applications. From dog toys to detergent bottles, the co-extrusion application is one of the most important aspects of the packaging manufacturing industry.
