Final Report: Biodegradable Thermoplastic Natural Fiber Composite

EPA Contract Number: EPD07039
Title: Biodegradable Thermoplastic Natural Fiber Composite
Investigators: Li, Yan
Small Business: NaSource Company
EPA Contact: Manager, SBIR Program
Phase: I
Project Period: March 1, 2007 through August 31, 2007
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2007) RFA Text |  Recipients Lists
Research Category: SBIR - Green Buildings , Small Business Innovation Research (SBIR)

Summary/Accomplishments (Outputs/Outcomes):

Because industrial byproduct lignins are usually brittle and weak materials with high Tg, they would be burned before melting and thus cannot be melt-processed into useful objects. This project proposed that chemical modifications are necessary to modify lignin’s structures to obtain desirable thermal and materials properties, and fiber reinforcement could be a good way to improve the strengths of lignin-based polymeric materials. Thus, the Phase I research work was planned and carried out in two main steps. First, the lignin was chemically modified in attempts to obtain desirable thermal and materials properties that allow the modified lignin to be formulated into thermoplastic resins with adequate mechanical strengths. Second, the resins were reinforced with natural plant fibers to form the proposed biodegradable composites.

Novel chemical reactions were applied to modify an industrial kraft lignin. Experiment conditions were found to ensure the chemical modifications at specific lignin structures, and the reactions were verified by ultraviolet (UV)-visible measurements and Fourier Transform Infrared Spectroscopy (FTIR) analysis. Various experiments were carried out in an attempt to improve the extent of the chemical reactions. Specifically, modified lignins have shown significant improvements in thermal melting behavior and miscibility/compatability with other polymers that can serve as polymeric plasticizers.

Resin formulations based on blends of modified lignins and certain polymeric plasticizers were created. The resins were melt-processable. Composites with various resin/fiber ratios were prepared. Synergy effects were observed as a result of compositing lignin thermoplastic resins with fibers. The strengths of the resins can be improved by fiber reinforcement in the composites which could overcome the drawbacks of lignin polymeric materials. Thus, the composites made feature lignin resins as the continuous matrix, and the filling natural fibers reinforce the strengths of the resins. They are different from conventional wood-based composite materials such as plywood, particle board, and fiberboard.

The polymer nature of the lignin samples and constraints in conformational changes in lignin structures were found to limit the extent of certain chemical reactions. Low molecular weight volatile compounds in lignin samples also showed negative effects in melt processing the resins and the composites.

Conclusions:

Novel chemical reactions were applied to modify the properties of industrial byproduct lignins. The modified lignin preparations have shown improved thermal melting behavior and compatibility with certain polymers. Miscible blends based on these modified lignins were formulated for use as resins for making thermoplastic lignin-natural fiber composites. The lignin based resins exhibited excellent wetability and adhesion to the plant fibers, a significant advantage over other synthetic polymer-natural fiber composites in which fiber-matrix adhesion is generally poor. The thermoplastic lignin-natural fiber composites can be easily melt-processed by injection molding or heat-pressing. Further improvements in the mechanical properties of the composites are expected to come from fractionation of lignin samples to remove low molecular weight volatile compounds before chemical modification, more efficient synthetic methods to enhance the specific chemical transformations of lignin structures and thus afford desirable materials properties, and better plasticization and formulation of modified lignin-polymer blends.

The composites will be low-cost since the process uses the byproduct lignins and applies simple chemical modification methods. Low cost and biodegradability will be the driving forces for the composite’s future commercial success.

Supplemental Keywords:

small business, SBIR, EPA, natural fiber composite, thermoplastic composite, biodegradable composite, biocomposite, bioplastics, lignin-based plastics, green building materials, lignin-plant fiber composites, thermoplastic lignin resin, Fourier Transform Infrared Spectroscopy, FTIR,, RFA, Scientific Discipline, Sustainable Industry/Business, Environmental Chemistry, Sustainable Environment, Technology for Sustainable Environment, Chemistry and Materials Science, Environmental Engineering, plant fiber composites, green building design, alternative building technology, alternative materials, biocomposite