A Composition and a Method for Preparing PLA with Improved Performance Characteristics
There is a growing trend in the plastics industry towards utilizing sustainable materials and processes for polymer production. This trend is driven by social, political, economical, and environmental concerns motivating a desire to lessen dependency on petroleum-derived products. Polylactic acid (PLA) is growing rapidly in popularity as an alternative to petrochemical-based plastics. It is biodegradable, thermoplastic, and derived from renewable resources. However, there are several major drawbacks associated with PLA, including low elongation at break, poor impact strength and heat deflection temperature. Plasticizers are used to overcome the brittleness of PLA, but plasticizers tend to leach out over time. Hence, there is a need for compositions and methods that will improve upon these limiting characteristics. Such improvements will broaden the use of PLA and hasten its displacement of petroleum-derived plastics.
Description of Technology
This invention provides a composition and a method for preparing PLA with improved performance characteristics. The composition contains a biodegradable polyester polymer of a hydroxyl acid monomer, a hyperbranched dendritic polymer, and optionally an organoclay or natural fibers. The hyperbranched polyester is hydroxyl functional aliphatic polyester with a tree like structure with a core polyalcohol from which other multifunctional compounds as repeating units extends. The hyperbranched polymer itself has poor mechanical properties due to lack of chain entanglement. An in-situ modified hyperbranched polymer with a low content of anhydride functional compounds is used for blending with PLA. The modified hyerbranched polyester is key to providing improved toughness, stiffness, thermal stability, and high reactivity to the polymer polymers, without significantly reducing their tensile strength and modulus.
- Compositions have improved performance characteristics when compared to non-hyperbranched Polyesters: The polymer exhibits excellent miscibility, improved impact strength and elongation. They are highly reactive and effective even at low concentrations. All of this is achieved without drastically decreasing tensile strength and modulus.
- Biodegradable: Hyperbranched Polyesters are aliphatic and have low molecular weights.
This invention is useful for producing PLA with improved performance characteristics. The composition is useful as a high performance bio-polymeric alternative to conventional thermoplastics such as polypropylene and polyethylene for packaging, automobile, household, medical and agricultural applications.
US 2006/0247387 A1 (filed Apr 28, 2006)
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Michigan State University