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Can any plastic soda bottles be recycled back into their original containers? Is this at a rate of 25% or 50% or higher.

PET plastic beverage bottles can be – and are being – recycled back into beverage bottles.  (I don’t have data on the rate at which this is occurring.)  But not always.

The answer to your question has to do with how products made from plastics (bottles, bags, etc.) are collected for recycling and processed into raw material for reuse.

Plastic beverage bottles are collected, washed, shredded/chopped, melted and extruded to create new plastic pellets. These pellets (about the size of bb’s) are the basic raw material that companies buy to melt and shape into new products or packaging. These recycled plastic pellets are made available for sale to companies willing to pay the going rate for the material.

As you can see, this is where another class (economics) comes into play.

Bottles made into bottles is one option for recycled plastic – but not the only one. Let’s say, for example, the plastic bottle recycling facility is right next door to a plant that makes clothing. That clothing company may want to get its raw material (polyester plastic) from its neighbor to make t-shirts, in part because there are no shipping costs for the pellets.

In some cases, there may be extra costs involved to make sure the pellets can be used for certain things. For example, to turn plastic from a food or beverage container into another food and beverage container, it would be important to make sure that the plastic has been sanitized for the new use. This may mean that the plastic would need to be melted at a higher temperature. It may make more economic sense in this case to use the recycled plastic to make carpeting, for example, instead of bottles.

Do plastics decompose back into constituent elements or are they incapable of biological decomposition?

The biodegradability of plastics is an extremely intriguing area of research that is currently being investigated by many laboratories in academic and industrial settings around the world.

When considering if plastic is “biodegradable,” we must first take into account what is meant by the word “plastic.”   Two types of plastic are commonly used in consumer goods: thermoplastics and thermosetting polymers.

Thermoplastics are plastics that melt at elevated temperatures and are then formed into usable shapes; examples include grocery bags, plastic bottles, and other consumer goods.  Typically, thermoplastics are composed of very long chains of carbon atoms and incorporate different trace chemicals that impart certain properties into the polymer.  These long carbon chains are difficult for microbes to eat as an energy source because carbon bonds are very strong atomic bonds.  However, thermoplastics can degrade in the presence of UV light, such as sunlight, or under certain chemical conditions.  Under “natural” conditions, thermoplastics will take a long time to degrade.  Despite the resistance to degradation, thermoplastics are easily recycled.

Thermoset plastics are different in that the polymer is formed from a reaction between two different types of molecules, creating long molecular chains.  Common examples include foam padding and insulation made from polyurethanes.  These types of plastics cannot be heated and reformed as they are “set” after the reaction takes place.  The polymer chains are comprised of various carbonyl bonds that are much easier for microbes to use as an energy source than carbon chains.  Eventually, the polymers can degrade into their initial components, such as alcohols, amines, and carboxylic acids.  That said, the ability of the thermoset polymer to biodegrade will depend greatly on the environmental conditions, trace constituents, and polymer composition.

I hope this answer helps. Thanks for your question!

Professor Plastic

what plastics /rubbers besides medical grade silicone are acceptable. currently used for mouth pieces

Thank you for your inquiry.  To find out what kind of plastic is used in a specific mouth guard or dental work, you may want to call the manufacturer or consult with your prescribing dentist or doctor.  A mouth guard is generally for sports/athletic protection or serves a medical/dental purpose, such as to prevent teeth grinding.  Some mouth guards, such as those used for protection in sports events, are made from a plastic called EVA (ethyl vinyl Acetate).  Soft “night guards” could be made from silicone or other plastics.  ASTM classifies athletic/sports mouth guards in three categories; this standard may provide additional useful information to you.  See ASTM F697-00, standard practice for care and use of athletic mouth protectors.

Thanks for your question!

Professor Plastic