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2005 Progress Report: Enhancing Properties of Polylactides
EPA Grant Number: R831530Title: Enhancing Properties of Polylactides
Investigators: Knauss, Daniel M. , Dorgan, John R.
Institution: Colorado School of Mines
EPA Project Officer: Richards, April
Project Period: February 1, 2004 through January 31, 2007 (Extended to January 31, 2008)
Project Period Covered by this Report: February 1, 2005 through January 31, 2006
Project Amount: $335,000
RFA: Technology for a Sustainable Environment (2003)
Research Category: Pollution Prevention/Sustainable Development
Description:
Objective:Polylactides (PLA) are a family of environmentally benign bioplastics based on renewable resources. The environmental advantages are numerous and include: (1) production of the monomer from a renewable resource (biomass), (2) sequestration of vast quantities of the greenhouse gas carbon dioxide, (3) energy savings and accompanying pollution prevention, and (4) reduction of municipal landfill volumes. PLA polymers have a unique combination of favorable economic, energy, and environmental benefits.
The overall objective of the research project is to improve the properties of PLA so that these environmentally benign polymers may be more widely used. Important technical obstacles are hindering the acceptance of polylactides for use in some applications. For example, the heat distortion temperature of PLA is low, PLA is too brittle for some applications, the rheological (flow) properties of the material are not suited for important applications like paper coating, and the permeation properties of PLA are too high for certain packaging applications. This research project pursues multiple approaches for modifying the properties of PLA, including the preparation of micro and nanocomposites, the control of polymer architecture, and the synthesis of core-shell micro- and nanoparticles.
Progress Summary:Branched architectures of PLA have been prepared by the copolymerization of lactide and functionalized epoxides. We have been able to produce materials with an average of between three and five branches that exhibit decreased intrinsic viscosity values relative to linear polymers of similar molecular weight.
PLA shell-crosslinked polyurethane core micro- and nanoparticles have been produced as a means of modifying PLA. PLA particles have been produced in the size range from 100 nm to 1 micron in diameter with varying compositions by a simple one-pot method. The particles have been characterized by size exclusion chromatography, light scattering, and electron microscopy. The particles can ultimately be dispersed into bulk PLA for impact resistance improvement and flow modification.
Reactive compatibilization of cellulosic fibers with PLA has been demonstrated using cellulosics from woody plants. Grafting has now been completed between PLA and wood fibers—these fibers reinforce the PLA matrix, and so we have created the first example of a reactively compatibilized microcomposite based on 100 percent renewable materials. Hydroxyl groups available on the surface of cellulosic fibers are used to initiate lactide polymerization. Various processing strategies are investigated: (1) blending preformed PLA with the fiber material; (2) polymerizing lactide through a one-step process in the presence of the fibers alone; or (3) performing reactive compatibilization in the presence of preformed high molecular weight polymer. The results thus far show that materials prepared by simultaneous introduction of lactide and preformed high molecular PLA at the beginning of the reaction possess superior mechanical properties compared to composites made by either purely mechanical mixing or solely polymerization of lactide in the presence of fibers.
As part of the composite work, a new Fourier transform infrared (FTIR) spectroscopy method for measuring lactide concentration in a PLA matrix was developed. The lactide ring breathing mode peak at 935 cm-1 is rationed against the asymmetric bending mode of methyl groups at 1454 cm-1 because the methyl group is present both in lactide monomer and the polymer, this ratio provides a direct measure of lactide concentration. The advantages of using FTIR for conversion analysis are numerous and include high sensitivity as well as low cost. In addition, instrumentation is readily available allowing on-line measurements during film processing as well as in situ monitoring of polymerization reactions. The new technique thus enables rapid measurements without the necessity of materials sampling and is therefore ideally suited for online process control of industrial processes.
The close collaboration between the faculty team members also led to the development and publication of a review article for an American Chemical Society Symposium Series 939 on Degradable Polymers published in 2006.
Conclusions
The research has successfully resulted in the development of new PLA architectures, including branched and hyperbranched, core-shell micro- and nanoparticles, and microcomposite structures with cellulosics. Detailed results can be found in the publications listed below. The materials are being evaluated for the effect on PLA properties. The branched PLA has potential in melt flow modification, the particles for impact modification, and the microcomposites for improved heat distortion temperatures and structural materials. The funding has provided financial support and training for three graduate students: Ms. Birgit Braun, Mr. Louis Pitet (M.S., August 2006), and Mr. Kevin McNamee.
Future Activities:The investigators did not report any future activities.
Journal Articles on this Report: 5 Displayed | Download in RIS Format
| Other project views: | All 22 publications | 8 publications in selected types | All 7 journal articles |
| Type | Citation | ||
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Bao L, Dorgan JR, Knauss D, Hait S, Oliviera NS, Maruccho IM. Gas permeation properties of poly(lactic acid) revisited. Journal of Membrane Science 2006;285(1-2):166-172. |
R831530 (2005) |
not available |
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Braun B, Dorgan JR, Dec SF. Infrared spectroscopic determination of lactide concentration in polylactide: an improved methodology. Macromolecules 2006;39(26):9302-9310. |
R831530 (2005) R831530 (Final) |
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Braun B, Dorgan JR, Knauss DM. Reactively compatibilized cellulosic polylactide microcomposites. Journal of Polymers and the Environment 2006;14(1):49-58. |
R831530 (2004) R831530 (2005) R831530 (Final) |
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Hutchinson MH, Dorgan JR, Knauss DM, Hait SB. Optical properties of polylactides. Journal of Polymers and the Environment 2006;14(2):119-124. |
R831530 (2005) |
not available |
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Oliveira NS, Dorgan J, Coutinho JAP, Ferreira A, Daridon JL, Marrucho IM. Gas solubility of carbon dioxide in poly(lactic acid) at high pressures. Journal of Polymer Science Part B-Polymer Physics 2006;44(6):1010-1019. |
R831530 (2005) |
not available |
composite, renewable, bio-based materials, natural fibers, bio-polymer, chemical synthesis, sustainable industry/business, chemistry, chemistry and materials science, engineering, new/innovative technologies, sustainable environment, technology for sustainable environment, cleaner production/pollution prevention, environmental sustainability, environmentally applicable nanoparticles, branched, hyperbranched, dendritic, topology, molecular architecture, adhesives, alternative materials, carbon dioxide, renewable resource, resins, polymer design, polymerization chemistry,
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INTERNATIONAL COOPERATION, Sustainable Industry/Business, Scientific Discipline, RFA, POLLUTION PREVENTION, Technology for Sustainable Environment, Sustainable Environment, waste reduction, Energy, Chemicals Management, Environmental Engineering, Environmental Chemistry, biomass, life cycle analysis, green chemistry, waste minimization, environmentally conscious manufacturing, life cycle assessment, environmentally friendly green products, energy efficiency
Relevant Websites:
http://www.mines.edu/academic/chemistry/faculty/knauss/
http://www.mines.edu/academic/chemeng/faculty/jdorgan/
Progress and Final Reports:
2004 Progress Report
Original Abstract
Final Report