Utilization of TEMPO-oxidized celluloses in bio-based nanocomposites is reported for the first time. TEMPO-oxidized wood pulps (net carboxylate content 1.1 mmol/g cellulose) were fibrillated to varying degrees using a high intensity ultrasonic processor. The degree of fibrillation was controlled by varying sonication time from 1 to 20 min. The sonication products were then characterized independently and as fillers (5 wt% loading) in hydroxypropyl cellulose nanocomposite films. Nanofibril yields ranging from 11 to 98 wt% (on fiber weight basis) were obtained over the range of sonication times used. Suspension viscosities increased initially with sonication time, peaked with gel-like behavior at 10 min of sonication and then decreased with further sonication. The thermal degradation temperature of unfibrillated oxidized pulps was only minimally affected (6°C decrease) by the fibrillation process. Dynamic mechanical analysis of the nanocomposites revealed strong fibril-matrix interactions as evidenced by remarkable storage modulus retention at high temperatures and a suppression of matrix glass transition at ''high'' (*5 wt%) nanofibril loadings. Creep properties likewise exhibited significant (order of magnitude) suppression of matrix flow at high temperatures. It was also believed, based on morphologies of freeze-fracture surfaces that the nanocomposites may be characterized by high fracture toughness. Direct fracture testing will however be necessary to verify this suspicion.

Amidation and ionic complexation were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONc), using octadecylamine (ODA) as the modifying compound. Effects of the two treatments on TONc with respect to degree of ODA substitution, surface hydrophobicity, crystalline characteristics, and thermal decomposition properties were investigated, respectively, with elemental analysis, contact angle measurements, X-ray diffraction spectroscopy, and thermogravimetric analysis. Both treatments resulted in complete substitution of TONc surface carboxyl groups with ODA, transforming TONc surfaces from hydrophilic to hydrophobic. A slightly greater than one-to-one ODAto-carboxyl ratio was found for the ionic complexation product, giving it a more hydrophobic character than the amidation product. Furthermore, the ionic complexation product was found to be surprisingly stable in acidic environment and was able to resist dissociation at fairly low pH. TONc from both treatments could be readily dispersed in organic solvents of wide-ranging polarities, making ionic complexation an equally effective surface modification approach as amidation for the hydrophobization of TONc surfaces. It was also found, through X-ray diffraction results that the crystalline structure of TONc was preserved even after the surface modification treatments. Finally, the thermal stability of TONc was slightly increased as a result of the surface modification treatments as evidenced by slight shifts to higher values of TONc thermal decomposition temperature.

A method has been developed for the quantitative determination of the composition of thermoplastic wood composites. The method involves area measurements of the two peaks in the derivative curve of a tracing produced by the thermogravimetric analysis (TGA) of a thermoplastic composites sample in an inert atmosphere. This may involve the standard, constant heating rate method or the high resolution (Hi-Res™) TGA method; both produce virtual baseline separation between wood and polyolefin peaks over a wide compositional range. Because this baseline separation suffers from a mutual effect on the thermal degradation of wood and polyolefins, best results are obtained if the parameters relating peak area with polyolefin content are different below and above 40% polyolefin content.

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