From Green Plastics
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Polymers are long molecules. They are one of the basic components of all plastics.
Synthetic polymers
Synthetic polymers are polymers that are man-made. Most synthetic polymers are manufactured from petroleum.
Some examples of synthetic polymers include:
- polystyrene is the polymer found in styrofoam, used for everything from packing materials and insulation to drinking cups.
- polyvinyl chloride, widely known by its abbreviation PVC, is used in a lot of building material (and is well-known as being ubiquitous in piping).
These materials are generally not biodegradable, and because they are made from petroleum, once the basic materials for creating them are used up, we cannot make any more.
Biopolymers
Biopolymers are polymers that occur in nature. Carbohydrates and proteins, for example, are biopolymers. Many biopolymers are already being produced commercially on large scales, although they usually are not used for the production of plastics. Even if only a small percentage of the biopolymers already being produced were used in the production of plastics, it would significantly decrease our dependence on manufactured, non-renewable resources.
Some examples of biopolymers include:
- cellulose is the most plentiful carbohydrate in the world; 40 percent of all organic matter is cellulose!
- starch is found in corn (maize), potatoes, wheat, tapioca (cassava), and some other plants. Annual world production of starch is well over 70 billion pounds, with much of it being used for non-food purposes, like making paper, cardboard, textile sizing, and adhesives.
- collagen is the most abundant protein found in mammals. Gelatin is denatured collagen, and is used in sausage casings, capsules for drugs and vitamin preparations, and other miscellaneous industrial applications including photography.
- casein, commercially produced mainly from cow's skimmed milk, is used in adhesives, binders, protective coatings, and other products.
- soy protein and zein (from corn) are abundant plant proteins. They are used for making adhesives and coatings for paper and cardboard.
- polyesters are produced by bacteria, and can be made commercially on large scales through fermentation processes. They are now being used in biomedical applications.
A number of other natural materials can be made into polymers that are biodegradable. For example:
- lactic acid is now commercially produced on large scales through the fermentation of sugar feedstocks obtained from sugar beets or sugar cane, or from the conversion of starch from corn, potato peels, or other starch source. It can be polymerized to produce polylactic acid.
- triglycerides can also be polymerized. Triglycerides make up a large part of the storage lipids in animal and plant cells. Over sixteen billion pounds of vegetable oils are produced in the United States each year, mainly from soybean, flax, and rapeseed. Triglycerides are another promising raw material for producing plastics.
These natural raw materials are abundant, renewable, and biodegradable, making them attractive feedstocks for bioplastics.
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