No abstract

Variability in the chemical composition of surface properties of various wood fibers (eastern white cedar, jack pine, black spruce, and bark) was investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and X-ray photoelectron spectroscopy (XPS). Both DRIFTS and XPS showed high variability in fiber surface composition between species and between fiber types (sapwood, heartwood, and bark). Fiber surface was modified by esterification reaction using a maleic anhydride polyethylene (MAPE) treatment. DRIFTS failed to assess surface modification, whereas XPS results showed that MAPE treatment increased the surface hydrocarbon concentration of jack pine wood fiber, indicated by a decrease in oxygen-carbon ratio and an increase in relative intensity of the C1 component in the C1s signal. Lignin concentration variability on the fiber surface was determined as the major factor that prevents esterification from taking place.

ABSTRACT:The thermal sensitivity, nucleating ability, and nonisothermal crystallization of high-density polyethylene (HDPE) with different wood fillers during wood/HDPE melt processing were investigated with thermogravimetric analysis and differential scanning calorimetry. The results showed that the wood degraded at a lower temperature than HDPE. The thermal decomposition behavior was similar across wood species. The most remarkable dissimilarities were observed between wood and bark in the decomposition rate around a processing temperature of 300 C and in the peak temperature location for cellulose degradation. The higher degradation rate for bark was explained by the devolatilization of extractives and the degradation of lignin, which were present in higher amounts in pine bark. The nucleating ability for various wood fillers was evaluated with the crystalline weight fraction, crystal conversion, crystallization halftime, and crystallization temperature of the HDPE matrix. The nucleation activity improved with the addition of wood particles to the HDPE matrix. However, no effect of wood species on the crystal conversion was found. For composites based on semicrystalline matrix polymers, the crystal conversion may be an important factor in determining the stiffness and fracture behavior.

Essential oils (EOs) were steam-extracted from the needles and twigs of balsam fir, black spruce, white spruce, tamarack, jack pine and eastern white cedar that remained after logging in eastern Canada. These EOs, similarly to that from Labrador tea and other commercial EOs from Chinese cinnamon, clove and lemon eucalyptus, exhibited many common constituent compounds (mainly α-pinene, β-pinene, limonene and bornyl acetate) making up 91% of each oil based on gas chromatography-mass spectrometry analysis. All of these oils exhibited antibacterial properties, especially when examined in closed tube assay compared to the traditional 96-well microliter format. These antimicrobial activities (minimum inhibitory concentration ≥ 0.2% w/v), comparable to those of exotic EOs, were shown against common pathogenic bacteria and fungi. The antioxidant potential of the boreal samples was determined by the 1,1-diphenyl-2-picrylhydrazyl radical scavenging (concentration providing 50% inhibition ≥ 7 mg/ml) and reducing power methods. Finally, this investigation revealed some boreal EOs to be potential antimicrobial and antioxidant agents that would notably benefit products in the personal hygiene and care industry.