Understanding Recycling Plastics

 

09.26.2016

0800

2016-06-29 18.07.48

Know Your Plastics

The Plastic Recycling Process

The plastic recycling process begins with sorting the various items by their resin content. The chart above shows the seven different plastic recycling symbols marked on the bottoms of plastic containers. The recycling mill sorts the used plastics by these symbols and may perform an additional sort based on the color of the plastic.

Once sorted, the plastics are chopped up into small pieces and chunks. These pieces are then cleaned to further remove debris like paper labels, residue from what was inside the plastic, dirt, dust, and other small contaminants.

Once cleaned, certain plastic pieces are melted down and compressed into tiny pellets called nurdles. Once in this state, the recycled plastic pellets are now ready to reuse and fashion into new and completely different products, as recycled plastic is hardly ever used to create the same or identical plastic item of its former self.

Does Recycling Plastics Work?

In a nutshell: yes and no. The plastic recycling process is fraught with flaws. Some of the dyes used in creating the plastic can be contaminated and cause an entire batch of potential recycling material to be scrapped. Additionally, there are still a large percentage of people who refuse to recycle, thus the actual numbers of plastics being returned for reuse is roughly 10% of what is purchased as new by consumers.

Another issue at stake is the fact that producing recycled plastic does not reduce the need for virgin plastic. However, plastic recycling can and does reduce the consumption of other natural resources like timber, due to its use in making composite lumber and many other products.

The 5-Step Process for Plastic Recycling

1. Collection – The recycling facilities gather available recyclable plastic material in their area, such as from roadside collections, special recycling bins, or even directly from industries. In this way, both post-consumer and post-industrial plastic items are collected.
2. Manual sorting – All plastic items that are collected are then sorted according to the various plastic types indicated by the plastic recycling symbols and codes on them. Unwanted non-plastic materials found in the piles are promptly taken out.
3. Chipping – After sorting, the sorted plastic products are prepared for melting by being cut into small pieces. The plastic items are fed into a machine which has sets of blades that slice through the material and break the plastic into tiny bits.
4. Washing – At this step in the process of recycling plastic, all residue of products originally contained in the plastic items and various other ‘contaminants’ (e.g. paper labels, dirt) are removed. A particular wash solution consisting of an alkaline, cationic detergent and water are used to effectively get rid of all the contaminants on the plastic material, making sure that all the plastic bits are clean and ready for the final step.
During washing, the wash tank agitator serves as an abrasive, stripping the adhesive off any labels and shredding any paper mixed in with the plastics. The alkaline, cationic detergent (which is similar to the formulas used in shampoos and fabric softeners) is used because plastic materials have a positive surface charge, and only positively-charged chemical compounds (which in this case are cationic detergents) can properly clean them, and effectively remove dirt and grease from the positively charged plastic surfaces.

5. Pelleting – The cleaned and chipped pieces of plastic are then melted down and put through a machine called an ‘extruder’ in this stage of the recycling plastic process. The extruder shapes the melted plastic into thin noodle-like tubes. The plastic tubes are then cut into small pellets by a set of rotating knives. The pellets are then ready to be reused and remade into new items.

What About the Bag?

Plastic bags go through the same five-step process as other plastic products. They too are sorted into their various plastic types, washed and rinsed. However, in the case of plastic bags, they are chopped rather than chipped. The chopped shreds of plastic bags are then melted down during the pelleting stage.
What’s Next?

The plastic pellets derived from the recycling plastic process are usually sold by the recycling company to other businesses which would then mold the plastic pellets into an assortment of plastic products for various uses. Some products use a combination of recycled plastic pellets and virgin plastic ones.

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