Recycling

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Solids

(Current Recycling Technology and Processes)

Plastic Recycling Process  (Page 1)

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The recycling of plastic is important because plastic is not biodegradable, which means it will not dissolve on its own if it is buried as a landfill.  Plastics will only contaminate the soil that it is in.  If they are dumped into water channels, flow into rivers and eventually oceans, different form of plastics can strangle or choke sea animals to death.  To avoid such misfortunes to the environment, we need to recycle plastics.  The recycling process of plastics is quite complicated.  The foremost issue of this process is to sort out the different type of plastics, since different plastics may require different treatment.  For a complete list of today’s recyclable plastic materials, please visit our section Current Recyclable Materials - Plastics. The practice of sorting is included as part of the Pre-granulation Process.  When all of the plastics are sorted, sawed, stripped, and shredded, they go through a granulation process where plastics are grounded into small and irregular pieces.  After granulation, different plastic grounds are blended and compounded into new products.  Following is a detailed explanation of the plastic recycling process. PRE-GRANULATION PROCESSES Usually when plastic scraps are collected for recycling, everything comes in a big pile. In order to process different polymers, they should first be separated and all of the attached metal parts, labels, dirt and dust should be removed.  After this entire cleaning stage, the scraps need to be reduced into suitable dimensions to fit the throat of the granulation equipment.  This entire process explained above is referred to as the Pre-granulation processes.  The following list details what is involved the main processes. Sorting  Different components of differing polymers are identified and separated into different categories.  This allows different polymer types to be processed separately and result in the highest quality of feedstocks. Sawing Sawing of plastic is done to the molded or extruded components of the scrapes that are too large to fit into the granulation machines. Stripping Many of the post-consumer or post-industrial plastic components have been assembled into products that may include metal parts, different polymer types, and paper labels.  As a result, we need to “strip out” or remove these extraneous items in order to maintain the quality of the resulting feedstock. Shredding Shredding utilizes a spinning rotor that cuts and reduces the bulky plastic components into manageable sizes.  What comes out of this shredding process are irregular shaped and roughly cut product that is still too big to be used in the compounding processes.  This is also the reason why shredding and granulation are used in conjunction to provide feedstock in the most efficient and proficient manner.

Figure: Shredder rotor blade. [Courtesy of: VAL-FAB, Inc.]

GRANULATION Granulation is a similar process to shredding that uses spinning blades to cut the plastic components into irregular shapes.  These irregular shapes are commonly referred as the “reground” or “regrind”. The slight edge granulation holds of shredding is the fact that it can actually control the approximate size of the reground that is fitting for later compounding processes.  Usually, a sample of the “reground” is taken and sent to a technical center after granulation.  At the center, a variety of test will be performed to establish the grades of thermoplastic compound that the material is best suited too.

Figure: Granulators. [Courtesy of: Consonic.]

Figure: "Reground" from the Granulation process. [Courtesy of: New Life Plastic Recycling, Inc.]

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QUICK LINKS (Specific Table of Contents): Section I: Introduction Section II: Present (YOU ARE CURRENTLY IN THIS SECTION) Section III: Future

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