Grantee Research Project Results
2004 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, 2004 through January 31, 2005
Project Amount: $335,000
RFA: Technology for a Sustainable Environment (2003) RFA Text | Recipients Lists
Research Category: Nanotechnology , Sustainable and Healthy Communities , Pollution Prevention/Sustainable Development
Objective:
Polylactides (PLA) are a family of environmentally benign plastics based on a monomer produced by the fermentation of corn. The environmental advantages of these polyesters 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 economic, energy, and environmental benefits.
The overall objective of the proposed effort is to improve the properties of PLA so that these environmentally benign polymers may be used in the place of more deleterious plastics. Important technical obstacles are hindering the acceptance of polylactides for use in some applications. For example, the heat distortion temperature of PLA is too low and PLA is too brittle for some applications. In addition, the rheological (flow) properties of the material are not suited for important applications like paper coating. The permeation properties of PLA are also too high for certain packaging applications. These are surmountable technical challenges because nanocomposites are known to increase the heat stability and decrease the permeability of plastic materials. These nanocomposites consist of nanometer-sized (a billionth of a meter) particles dispersed throughout a plastic matrix. Rheological properties can be improved by modifying the molecular architecture of the base polymer to impart specific responses.
Progress Summary:
Branched architectures of PLA have been prepared by the copolymeriztion of lactide and functionalized epoxides. We have been able to produce materials with an average of between 3 and 5 branches that exhibit decreased intrinsic viscosity values relative to linear polymers of similar molecular weight.
Polyester shell/crosslinked polyurethane core nanoparticles have been produced as a means of modifying PLA. The nanoparticles can ultimately be dispersed into bulk PLA. Investigations thus far have focused on polycaprolactone (PCL) as the polyester component, but the results demonstrate that the reaction can be extended to PLA polymers.
Reactive compatibilization of cellulosic fibers with PLA also is being pursued. We are using cellulosics from woody plants and starches from agricultural crops. The graft copolymers we are making have higher heat distortion temperatures than PLA alone. 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 being investigated: (1) blending preformed PLA with the fiber material; (2) a one-step process in which lactide is polymerized in the presence of the fibers alone; and (3) 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. Detailed results can be found in the publication listed below.
Future Activities:
Ecological concerns are a predominant theme for the 21st century; humanity must develop sustainable systems for materials and fuels. Biologically derived and inspired materials offer hope for achieving this important goal. Nanotechnology is rapidly expanding and its convergence with both biology and ecology is now being recognized. Ecobionanocomposites are a new class of materials that exploit this triple convergence of technologies. Presently, we are working in part to develop this new class of materials. In the near future, we will begin to study the melt flow behavior and other properties of the branched PLA. The synthesis of PLA/polyurethane nanoparticles will be accomplished and the properties of the materials investigated. Further research of the cellulosic microcomposites will investigate other sources of cellulosic fibers and modifications to the grafting procedures.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 27 publications | 10 publications in selected types | All 9 journal articles |
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Type | Citation | ||
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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) |
Exit Exit |
Supplemental Keywords:
composite, renewable, bio-based materials, natural fibers, bio-polymer, chemical synthesis, scientific discipline, 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,, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Sustainable Industry/Business, POLLUTION PREVENTION, Sustainable Environment, Energy, waste reduction, Environmental Chemistry, cleaner production/pollution prevention, Technology for Sustainable Environment, Chemicals Management, Environmental Engineering, life cycle analysis, environmentally conscious manufacturing, waste minimization, polylactides, biomass, energy efficiency, environmentally friendly green products, life cycle assessmentRelevant Websites:
http://www.mines.edu/academic/chemistry/faculty/knauss/
http://www.mines.edu/academic/chemeng/faculty/jdorgan/
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.