Biodegradable Plastics with High Glass Transition Temperatures Replace PET and Polystyrene
Beginning around 1995, the inventor took an interest in finding ways to make polymers from natural resources since it was apparent that petroleum-based polymers would eventually increase markedly in cost as the world reserves of petroleum diminished. An associate suggested they research making polymers from hydroxyl acids. This led to the idea of making polymers from lactic acid raw materials - the resultant polymers would be biodegradable. Years of experiments have resulted in novel biodegradable polymers with excellent material properties.
Description of Technology
The invention describes methods that generate biodegradable polymer (cyclic alkyl-substituted glycolides and polylactides ) structures that are derived from lactic acid precursors which are common by-products of fermentation processes. The required monomers can result from 2 or 3 step reactions using lactic acid as the starting raw material. The plastic compounds have molecular weights in the range of 40,000 to 100,000 grams per mole and glass transition temperatures over 100 degrees centigrade are easily achieved. The plastic compounds are expected to extrude and mold similar to their petroleum-based analogs, but will likely be more susceptible to degradation at very high temperatures.
- Renewable: These biodegradable polymer (cyclic alkyl-substituted glycolides and polylactides ) structures are derived from lactic acid precursors which are common by-products of fermentation processes.
- Environmentally friendly: In bulk volumes, PET and polystyrene are commonly used for packaging. PET is used for most disposable drink bottles and polystyrene is used for protective packaging. These alternates would provide the same function, but with the benefit of shorter lifetimes in post consumer waste streams (years instead of decades). The by-products of the degradation reaction are environmentally friendly and benign compounds very similar to amino acids.
The two materials of greatest interest in bulk quantities are those that appear to look and behave like polyethylene terephthalate (PET) and polystyrene. The biodegradable analog to polystyrene is a clear, glass material with glass transition temperatures in the range of 100 to 105 degrees centigrade. The analog polymer to PET has a crystalline structure at room temperature, has a melting point in the range of current PET materials, and also is clear. These polymers would be great for medical devices like pins and other supports that are used as temporary braces within the human body and would be counted upon to eventually degrade and be removed naturally by the body.
1 U.S. patent issued: 7,579,429
Gregory Baker, Milton Smith III, Feng Jing
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Michigan State University