Fabrication and Analysis of Polymeric Nanocomposites from Cellulose Fibrils

A novel process using high-intensity ultrasonication (HIUS) was developed to isolate fibrils from cellulose fibers. The geometrical characteristics of the fibrils were investigated using polarized light microscopy (PLM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Results show that small fibrils with diameter ranging from about thirty nanometers to several micrometers were peeled from the fibers. The degree of fibrillation of the fibers was significantly increased. The crystallinities or molecular structures of most of the cellulose materials were changed by HIUS treatment. To evaluate the fibrils degradation by HIUS, a method using AFM was modified and developed to measure the elastic modulus of single cellulose fibrils. The results indicated that it was necessary to consider the penetration of AFM tips to the cellulose fibril surfaces. In the diameter range of 150 to 300 nm, the elastic moduli of Lyocell fibrils did not have significant differences between the HIUS treatment time of 30 min and 60 min. The modulus of Lyocell fibrils with diameters from 150 to 180 nm was evaluated about 98 GPa and it decreased dramatically when the diameter was more than 180 nm. The elastic moduli of cellulose fibrils were not significantly different between isolation methods of HIUS and high-pressure homogenizer for pure cellulose fiber, between different cellulose sources of pulp fibers treated by homogenizer. The elastic modulus of fibrils from regenerated cellulose fibers was higher than that of natural fibers. The treated fiber and separated fibrils were used to reinforce poly(vinyl alcohol), poly(lactic acid), and polypropylene by film casting or compression molding. Both of the tensile modulus and strength of nano-biocomposites reinforced with treated fiber and separated fibrils were higher than those of the untreated fiber reinforced composites. The morphological characteristics of the nanocomposites were investigated with SEM, AFM, and PLM. The dispersion of fibrils was not perfect, and the adhesions between the polymer and fibrils were not good without further modification of the fibrils. The fibrils on the fibers and isolated from the fibers may be the role that the tensile modulus and strength of the treated fiber and separated fibril reinforced composites were higher than those of the untreated fiber

Bioenergy Properties of Juvenile Hybrid Poplars and Their Parent Species

Bioenergy properties of poplar species Populus trichocarpa (PT), Populus deltoides (PD), and their hybrid were evaluated. Hybrid poplar trees from the cross between PT and PD presented different anatomic, physical, chemical, and thermal properties from their parent species. Anatomic results tended to suggest that hybrid poplar, with fewer vessels per unit area, had more resemblance to PT. Extractive content ranged from 10.64-11% for PD, PT, and first-generation hybrid poplar, whereas it varied from 8.8-9.5% for backcross offspring (BC2-BC5). PD had the greatest average lignin content of 25.6% followed by first-generation offspring and backcross offspring with lignin content of approximately 25%. Holocellulose content of hybrid poplar species was higher than that of their parent species. Observed stem/stump proximate results ranged from 72-74.7%, 25-28%, and 0.80-1.7% for volatile matter, fixed carbon, and ash content, respectively. Heating values observed along the stem were slightly higher than at the stump, ranging from 7498-8356 kJ. TGA-FTIR analysis indicated that H2, CO2, CH4, and CO were the dominant gaseous components from wood pyrolysis

Tensile and Impact Properties of Steam-Exploded Wood-Polypropylene Composites

Wood-plastic composites were made from polypropylene and steam-exploded (SE) flour from small-diameter loblolly pine. SE wood content, maleic anhydride grafted polypropylene (MAPP) content, and extruder screw speed were investigated using an orthogonal test design to examine their effects on tensile and impact properties of the composites. The results showed that as SE wood-flour content was increased, the modulus of elasticity (MOE) of the composites also increased, whereas the tensile strength decreased. The MAPP content had a distinct effect on the tensile strength and no such effect on MOE; however, it had no clear trend for the impact properties of the composites. The wood content had distinct effects on both the tensile and impact properties of the composites. The screw speed also affected the tensile and impact properties of the composites

Technical Note: Melt Dispersion Technique for Preparing Paraffin Wax Microspheres for Cellulose Encapsulation

A practical and convenient approach for making paraffin wax microspheres with a melt dispersion technique was reported in this study. Surfactants were melted in water by water bath and then added to a flask after the wax was completely melted with stirring. Paraffin wax microspheres were generated by cooling. The obtained microspheres exhibited uniform diameters in the range of 10-60 μm observed with a scanning electrical microscope and were mainly dependent on the surfactant ratio. Encapsulated microcrystalline cellulose particles with the previously mentioned conditions were also generated and demonstrated the possibility of encapsulating microcrystalline cellulose with some acceptable agglomeration, although some encapsulated individually. Encapsulation of cellulose could be beneficial if agglomeration could be minimized and the encapsulated microcapsules could be dispersed during blending for wood composites manufacture

Microstuctural Changes in Wood-Plastic Composites (WPC) Due to Extended Moisture Cycling and its Relationship to Mechanical Performance Changes

The use of wood plastic composite (WPC) materials has been popular as a durable material for applications such as residential decking. For shoreline or ground contact installations, WPCs may be exposed to water for extended periods. Therefore water cycling is an important factor that may affect the properties of WPCs. In this study, a WPC, specifically extruded wood polypropylene composite, was studied. The moisture content, difhsion dynamics, bulk mechanical properties, and microstructural changes in the material subjected to soaking-drying cycles were investigated. The microstructure of the material in dry, wet and redried states was examined in three dimensions using an Xray microtomography (XMT). The uni-dimensional (ID) moisture diffusion coefficient (Dm) of thin specimens exposed to a high humidity environment was about 8xl0-~cm 2/sec. It needs at least 660 days in osmotic (fresh) water for this WPC of 3.25cm in thickness to be saturated and more in seawater because the D,, was about 1.5 times larger in osmotic water than in seawater. For ID, 2D and 3D diffusion tests soaked in water, the Fickian\u27s models did not fit the test data well and the diffusion behaviors may be non-Fickian7s for both types of water. It was found that water immersion reduced the flexural, tensile and compressive properties of the composite, but not impact resistance strength. After about 13 months immersion, there were significant differences (alpha=0.05) in flexural strength and MOE soaked in osmotic water among dry, wet and redried treatments, but no significant differences in flexural strength and some for MOE in seawater were found. There was no significant effect of water type on the ultimate tensile strength. However, there was a significant effect of water type on tensile MOE. The ultimate compressive strength and chord MOE decreased after 13 months of soaking and increased somewhat after redried for about seven weeks for both types of water. Most mechanical properties except the flexural MOR had both the existence of non-reversible damage and a recoverable portion, presumably related to wood modulus change from dry to wet and then redried. XMT was used to study the microstructural changes in dry, wet and redried states to detect the relationship between microstructural changes and the mechanical property changes. The smallest volume of 1513 pixels cube may be used to present the specimen using medians and means. There were some differences for both median and mean in three states. The cumulative distribution function was used to analyze voids in these three states assumed 230-255 intensity values as void and a 713 pixels cube was used to analyze the void distributions in the three states. The void volume increased from dry to redry and the cube position chosen affected the results greatly

WATER RETENTION VALUE MEASUREMENTS OF CELLULOSIC MATERIALS USING A CENTRIFUGE TECHNIQUE

A centrifugal method has been modified and applied to the assessment of water retention value (WRV) in cellulosic materials. Microcrystalline cellulose (MCC), small particles/fibrils isolated from MCC using high-pressure homogenizer, and pulp fibers saturated in water were centrifuged at different speeds and times with filter paper and/or a membrane acting as the filter in the WRV measurement setup. As centrifugal speed, time, and filter pore-size increased, lower WRVs were obtained. Smaller MCC particles/fibrils retained more water than the as-received MCC and pulp fibers. The results are useful for WRV measurements of cellulosic materials, especially for microfibrillated cellulose and small cellulosic fibrils

Lifting Wavelet Transform De-noising for Model Optimization of Vis-NIR Spectroscopy to Predict Wood Tracheid Length in Trees

The data analysis of visible-near infrared (Vis-NIR) spectroscopy is critical for precise information extraction and prediction of fiber morphology. The objectives of this study were to discuss the de-noising of Vis-NIR spectra, taken from wood, to improve the prediction accuracy of tracheid length in Dahurian larch wood. Methods based on lifting wavelet transform (LWT) and local correlation maximization (LCM) algorithms were developed for optimal de-noising parameters and partial least squares (PLS) was employed as the prediction method. The results showed that: (1) The values of tracheid length in the study were generally high and had a great positive linear correlation with annual rings (R = 0.881), (2) the optimal de-noising parameters for larch wood based Vis-NIR spectra were Daubechies-2 (db2) mother wavelet with 4 decomposition levels while using a global fixed hard threshold based on LWT, and (3) the Vis-NIR model based on the optimal LWT de-noising parameters ( R c 2 = 0.834, RMSEC = 0.262, RPD c = 2.454) outperformed those based on the LWT coupled with LCM algorithm (LWT-LCM) ( R c 2 = 0.816, RMSEC = 0.276, RPD c = 2.331) and raw spectra ( R c 2 = 0.822, RMSEC = 0.271, RPD c = 2.370). Thus, the selection of appropriate LWT de-noising parameters could aid in extracting a useful signal for better prediction accuracy of tracheid length

Primary Study of Woody Biomass and Coal for Energy Production Investigated by TGA-FTIR Analysis

The purpose of this study was to determine the pyrolysis characteristics and gas properties of woody biomass and coal. The main gases from the pyrolysis of biomass, coal, and mixtures of different ratios of the two were identified using TGA-FTIR. The evolution of gases and their characteristics were investigated in real time. Thermal analysis demonstrated that the biomass sources decomposed easily and that most of their weight was lost under lower temperatures than those of coal. TGA-FTIR analysis indicated that H2, CO2, CH4, and CO were the dominant gases released during the pyrolysis of biomass and mixtures. The results indicated that woody biomass could enhance coal pyrolysis or gasification and different types of biomass could have different influences on the thermal behavior of coal

The Effect of Layer Moisture Content Distribution on Lumber Surface and Bonding Interface Properties

This study investigated the effect of drying on moisture content (MC) distribution through ash lumber thickness, as well as the effect on wood surface and bonding at the interface. After the drying of lumber, the wood surface contact angles and free energy were collected over 6 days, and the MC difference (between surface and core) was measured. At the same time, the isocyanate adhesive strength, as well as the elemental composition of carbon (C1s), nitrogen (N1s), and oxygen (O1s) on the lumber surface and at the bonding interface, were tested daily. Both the wood surface contact angle and free energy changed with a change in MC difference. The O1s concentration at the bond interface decreased with increased MC difference, and the adhesive strength declined accordingly. To attain the best bond interface, the MC difference between the surface and core should be controlled within the range of 0.5 to 1%