jsbi writes: "Due to their molecular stability, plastics do not easily break down into simpler components. Plastics are therefore not considered biodegradable.However, researchers are working to develop biodegradable plastics that will disintegrate due to bacterial action or exposure to sunlight.
For example, scientists are incorporating starch molecules into some plastic resins during the manufacturing process. When these plastics are discarded, bacteria eat the starch molecules. This causes the polymer molecules to break apart, allowing the plastic to decompose. Researchers are also investigating ways to make plastics more biodegradable from exposure to sunlight. Prolonged exposure to ultraviolet radiation from the sun causes many plastics molecules to become brittle and slowly break apart. Researchers are working to create plastics that will degrade faster in sunlight, but not so fast that the plastic begins to degrade while still in use."