How to Remelt Plastic

Once sorted, plastic water bottles can be remelted and recycled.

Packaging material is one of the biggest contributors to garbage in the United States --- with plastic bottles, bags and styrofoam being some of the largest culprits. As a result, recycling is becoming a priority. More food and beverage manufacturers are incorporating remelted ecology-friendly packaging into their operations, according to the article "All About: Recycling Plastics." Recycling plastic involves the sorting, cleaning, and decontaminating of plastic trash, before it can be remelted and reused.

Things You'll Need

• Kiln
• Caustic soda
• Extruder

Instructions

1. Sort plastic by number. Plastic is a man-made material, and each container is marked with a number from one to seven that tells the resin identification code. The two most commonly melted plastics are polyethylene terphthalate (Number 1 plastics, such as soda bottles) and high-density polyethylene (Number 2 plastics, such as juice and milk bottles).

2. Inspect the plastic for contaminants. Foreign objects such as glass, rocks and debris need to be removed from the plastic trash. Then sort the plastics by color and shred the containers into flakes. Wash the plastic strips for 10 minutes, before adding caustic soda (sodium hydroxide) to the water at a one-to-one ratio.

3. Dry the plastic in a 175- to 200-degree Celcius rotating kiln. In the kiln the caustic soda will crystallize and peel away the surface layer of the plastic, which could have residual ink or paper from the previous packaging. After the drying process, the flakes should also be completely sterile and ready to be melted.

4. Load the plastic chips into an extruder. This machine funnels the plastic into a heating chamber -- a long narrow chamber that uses a screw to churn the plastic. The extruder melts the plastic at temperatures upwards of 275 degrees Celcius. As the screw turns, it also helps to push out the molten plastic through the die or mouth piece that determines its shape. Dies can create pellets, blocks or sheets of plastic.

5. Cool the plastic with water, which is often done with sprayers as the plastic is moved along on a conveyor belt. The plastic blocks and pellets are removed from the belt and left to air dry at a storage facility. Sheets of plastic are cut into uniformed sizes and layered before being stocked.

References

• "Recycling Plastic"; Nigel Croser; 2004
• BBC: "Plastic Recycling Comes Full Circle"
• CNN: "All About: Recycling Plastics"; Rachel Oliver; April 7, 2008
• "Recycling and Recovery of Plastics"; J. Brandrup; 1996
• Discover: "When Recycling Is Bad for the Environment"; Rachel Cernansky; July 6, 2009