Title page for ETD etd-08232004-164234


Type of Document Dissertation
Author Renneckar, Scott Harold
Author's Email Address srenneck@vt.edu
URN etd-08232004-164234
Title Modification of Wood Fiber with Thermoplastics by Reactive Steam-Explosion
Degree PhD
Department Wood Science and Forest Products
Advisory Committee
Advisor Name Title
Glasser, Wolfgang G. Committee Co-Chair
Zink-Sharp, Audrey G. Committee Co-Chair
Ducker, William A. Committee Member
Frazier, Charles E. Committee Member
Gatenholm, Paul Committee Member
Ifju, Geza Committee Member
Rials, Timothy Committee Member
Keywords
  • thermogravimetric analysis
  • fractionation
  • 13C NMR
  • confocal laser scanning microscopy
  • biopolymer
  • cellulose
Date of Defense 2004-06-18
Availability unrestricted
Abstract
For the first time, a novel processing method of co-refining wood and polyolefin (PO) by steam-explosion was scientifically explored for wood-thermoplastic composites without a coupling agent. Traditional studies have addressed the improvement of adhesion between components of wood thermoplastic composites through the use of coupling agents such as maleated PO. The objective of this study was to increase adhesion between wood and PO through reactive processing conditions of steam-explosion. PO characteristics, such as type (polyethylene or polypropylene), form (pellet, fiber, or powder) and melt viscosity were studied along with oxygen gas content of the steam-explosion reactor vessel. Modification of co-processed wood fiber was characterized in four studies: microscopy analysis of dispersion of PO with wood fiber, sorption properties of co-processed material, chemical analysis of fractionated components, and morphological investigation of co-processed material. Two additional studies are listed in the appendices that relate to adsorption of amphiphilic polymers to the cellulose fiber surface, which is one hypothesis of fiber surface modification by co-steam-explosion.

Microscopy studies revealed that PO melt viscosity was found to influence the degree of dispersion and uniformity of the steam-exploded material. The hygroscopic nature of the co-processed fiber declined as shown by sorption isotherm data. Furthermore, a water vapor kinetics study found that all co-refined material had increased initial diffusion coefficients compared to the control fiber. Chemical changes in fractionated components were PO-type dependent. Lignin extracted from co-processed wood and polyethylene showed PO enrichment determined from an increase of methylene stretching in the Fourier Transform infrared subtraction spectra, while lignin from co-processed wood and polypropylene did not. Additionally, extracted PO showed indirect signs of oxidation as reflected by fluorescence studies. Solid state nuclear magnetic resonance spectroscopy revealed a number of differences in the co-processed materials such as increased cellulose crystallinity, new covalent linkages and an alternative distribution of components on the nanoscale reflected in the T1ρ relaxation parameter.

Steam-explosion was shown to modify wood fiber through the addition of "non-reactive" polyolefins without the need for coupling agents. In light of these findings, co-refining by steam-explosion should be viewed as a new reactive processing method for wood thermoplastic composites.

Files
  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
  Appendices.pdf 1.02 Mb 00:04:43 00:02:25 00:02:07 00:01:03 00:00:05
  Chapter_3_Compositional_Analysis.pdf 172.48 Kb 00:00:47 00:00:24 00:00:21 00:00:10 < 00:00:01
  Chapter_4_Microscopic_Analysis.pdf 8.45 Mb 00:39:07 00:20:07 00:17:36 00:08:48 00:00:45
  Chapter_5_Sorption_Studies.pdf 1.99 Mb 00:09:11 00:04:43 00:04:08 00:02:04 00:00:10
  CHAPTER_6_Chemical_Changes.pdf 2.62 Mb 00:12:06 00:06:13 00:05:27 00:02:43 00:00:13
  Chapter_7_Morphological_Changes.pdf 290.06 Kb 00:01:20 00:00:41 00:00:36 00:00:18 00:00:01
  Chapter_8_Conclusions.pdf 12.94 Kb 00:00:03 00:00:01 00:00:01 < 00:00:01 < 00:00:01
  Dissertation_front.pdf 772.36 Kb 00:03:34 00:01:50 00:01:36 00:00:48 00:00:04
  vitae.pdf 3.92 Kb 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01

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