John Simonsen

Carbon nanofibers derived from cellulose nanofibers as a long-life anode material for rechargeable sodium-ion batteries

A highly reversible anode is indispensable to the future success of sodium-ion batteries (SIBs). Herein, carbon nanofibers (CNFs) derived from cellulose nanofibers are investigated as an anode material for SIBs. The CNFs exhibit very promising electrochemical properties, including a high reversible capacity (255 mA h g−1 at 40 mA g−1), good rate capability (85 mA h g−1 at 2000 mA g−1), and excellent cycling stability (176 mA h g−1 at 200 mA g−1 over 600 cycles).

Cellulose/DNA Hybrid Nanomaterials

Cellulose nanocrystals (CNXLs) have drawn attention from researchers for their remarkable reinforcing abilities and excellent mechanical properties. CNXLs typically have high aspect ratios of around 20-50 (length/width), low density of around 1.6 g/cc, high stiffness (135 to 155 GPa), and strength (estimated at 7500 MPa). Here we utilize CNXLs in a bottom-up hierarchical assembly to produce a macroscale material. Single-stranded oligonucleotides with an amino modifier were successfully grafted on CNXLs. The molecular recognition ability of the oligomeric base pairs was then utilized by duplexing complementary oligonucleotides grafted onto separate CNXL populations. The resulting hybrid nanomaterials were analyzed using dynamic light scattering, atomic force microscopy, and UV spectroscopy.

Creep resistance of wood‐filled polystyrene/high‐density polyethylene blends

Creep, the deformation over time of a material under stress, is one characteristic of wood-filled polymer composites that has resulted in poor performance in certain applications. This project was undertaken to investigate the advantages of blending a plastic of lower-creep polystyrene (PS) with high-density polyethylene (HDPE) at ratios of 100:0, 75:25, 50:50, 25:75, and 0:100. These various PS-HDPE blends were then melt blended with a short fiber-length wood flour (WF). Extruded bars of each blend were examined to measure modulus of elasticity and ultimate stress. Increasing the ratio of WF increased modulus of elasticity in all composites, except between 30 and 40% WF, whereas the effect of WF on ultimate stress was variable, depending on the composite. Scanning electron microscopic images and thermal analysis indicated that the wood particles interacted with the PS phase, although the interactions were weak. Finally, creep speed was calculated by using a three-point bending geometry with a load of 50% of the ultimate stress. Creep decreased only slightly with increasing WF content but more significantly with increasing PS content, except at pure PS. The WF/75PS-25HDPE blend showed the least creep.

Wood-fiber reinforcement of styrene-maleic anhydride copolymers

Styrene–maleic anhydride (SMA) copolymers containing either 7 or 14% maleic anhydride were filled with either pine flour or dry-process aspen fiber from a medium density fiberboard (MDF) plant. Material properties of the filled and unfilled SMA plastics were compared with those of aspen-fiber-filled and unfilled polystyrene (PS). The fiber-filled SMA composites were equivalent or superior to unfilled SMA in strength, stiffness, and notched Izod impact strength. Filled PS composites outperformed or matched the performance of filled SMA composites in the parameters tested. Unnotched Izod impact strength of filled polymers was generally inferior to that of the unfilled polymers. Water absorption from a 90% relative humidity exposure, a 24-h soak, and a 2-h boil showed mixed results when compared to the unfilled polymers. Dynamic mechanical analysis showed no change in glass transition temperature (Tg) after the addition of filler for either SMA or PS composites. The presence of the anhydride functionality on the polymer backbone did not appear to improve the strength of the composite. No evidence was found for chemical bond formation between the SMA and wood fiber.

Morphology and Properties of Wood-Fiber Reinforced Blends of Recycled Polystyrene and Polyethylene

Material properties of composites produced from recycled plastics and recycled wood fiber were compared. A blend of high-density polyethylene and polystyrene was used as a simulated mixed plastic. Stiffness was generally improved by the addition of fiber, as expected, but brittleness also increased. Pretreatment of the wood filler with phenol-formaldehyde resins did not significantly affect material properties. Differential scanning calorimetry indicated no interaction between the polyethylene phase and the other phases present in the composite. Glass transition temperatures for the various combinations of components indicated a possible interaction between the polystyrene phase and untreated wood filler. This was supported by scanning electron micrographs, which indicated a less-coalesced morphology for samples filled with treated wood flour compared to those with untreated wood flour.

Effect of extractives on the flexural properties of wood/plastic composites

This study investigated the effect of extractives in wood flour on the mechanical properties of wood-polypropylene (PP) composites. Three different solvents, acetone/water, dioxane/water and benzene/ethanol, were used to remove extractives in both pine and Douglas fir wood flour. X-ray photoelectron spectroscopy (XPS) confirmed that extraction resulted in a change in the surface composition of the wood flour. Differential scanning calorimetry showed no changes in the percent crystallinity of the PP matrix in the wood-PP composites and optical microscopy showed no detectable changes in PP spherulite size or shape between filled PP containing extracted and unextracted wood flour. A large increase in the strength of pine flour-PP composites was observed upon removal of extractives from pine flour. The Douglas fir flour-PP composites showed a smaller, but statistically significant, increase in strength upon removal of extractives, with the exception of the dioxane/water extracted Douglas fir. Significant differences were also observed in stiffness between extracted wood-PP and unextracted wood-PP composites with the exception of the dioxane/water extracted Douglas fir, which was not significantly different from the control.

Mechanical properties and creep resistance in polystyrene/polyethylene blends

Recycled plastics, predominantly high-density polyethylene (PE), are being processed in the shape of dimension lumber and marketed as plastic lumber. One drawback to these products is their low creep resistance or high creep speed. The objective of this study was to examine the feasibility of reducing the creep speed of PE-based products by blending the PE with a lower-creep plastic, in this case polystyrene (PS). Various blends of PE and PS were prepared in either a laboratory extruder or a bowl mixer and then compression-molded. The mechanical properties, creep behavior, morphology, and thermal properties of extruded and compression-molded samples were determined. The modulus of elasticity of the extruded blends could be estimated by a weighted average of PS and PE, even in the absence of a compatibilizer. Processing strongly affected the morphology and mechanical properties of the blends. For 50% PS: 50% PE blends, the stress-strain curves of the extruded samples showed PE-like behavior, whereas those from compression-molded samples were brittle, PS-like curves. Flexural strength was 50% higher in the extruded samples than in those from compression molding. The creep experiments were performed in three-point bending. Creep speed was lower in 50% PS: 50% PE and 75% PS: 25% PE blends than in pure PS. Creep speed of 75% PS: 25% PE was lowest of all the extruded blends. PE formed the continuous phase even when the PS content was as high as 50 wt %. For a 75% PS: 25% PE blend, cocontinuous phases were observed in the machine direction. A ribbonlike PS-dispersed phase was observed in the 25% PS: 75% PE and 50% PS: 50% PE samples. Blending low-creep-speed PS with high-creep-speed PE appeared to successfully improve the performance of the final composite.

Application of ionic liquids for electrostatic control in wood

Abstract Wood products with anti-electrostatic properties have wide applications in many fields. However, wood is an insulator and does not itself have anti-electrostatic ability. This study investigated several ionic liquids as anti-electrostatic agents for wood. Ionic liquids are liquids at room temperature (or close to room temperature), possess no vapor pressure and are excellent conductors for electric current. Maple and pine veneers were either soaked in or brushed with five ionic liquids: 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium hexafluorophosphate. The ionic liquid-treated wood specimens were then measured for surface resistivity and volume resistivity in accordance with ASTM standards. The effects of application method (brushed vs. soaked) and storage time were investigated. All the ionic liquids studied were effective anti-electrostatic agents for pine and maple. For all ionic liquids tested, pine had lower resistivity, and thus higher anti-electrostatic ability, than maple.

Utilizing straw as a filler in thermoplastic building materials

Abstract A recent addition to the list of composite building materials is plastic lumber. While utilizing recycled plastics as building materials promotes recycling, plastic lumber itself is a poor replacement for solid wood. Research is underway to improve the mechanical properties of wood/polymer composites. This report investigates the use of Willamette Valley rye grass straw as a filler in the commodity plastics polyethylene ( pe ) and polystyrene ( ps ). Since recycled plastics are often mixtures, blends of pe and ps were studied. A compatibilizer was used to improve the properties of the plastic blends. Composites of blends of plastics filled with straw showed a linear relationship in strength and stiffness. Straw performs similarly to wood as a filler in these systems. In composites containing only one plastic, the performance of straw as a filler seemed slightly superior to wood in polyethylene and slightly inferior in polystyrene. The properties observed here compare favourably to those of commercial products and suggest that improvements in these products are possible.

Improvement of interfacial adhesion between wood and polypropylene in wood-polypropylene composites

N-vinylformamide-grafted polypropylene (VFPP) was successfully synthesized through a free radical grafting reaction. Both polymeric methylene diphenyl diisocyanate (PMDI) and VFPP were effective compatibilizers for increasing both the strength and stiffness of the resulting wood–PP (polypropylene) composites. Both the modulus of rupture (MOR) and the modulus of elasticity (MOE) of the resulting wood–PP composites were further increased when PMDI and VFPP were used together as an integrated compatibilizer system. This new PMDI-VFPP compatibilizer system was comparable to maleic-anhydride-grafted polypropylene in terms of enhancing the strength and stiffness of the wood–PP composites. Study of the fractured surfaces of the wood–PP composites with scanning electron microscopy revealed that this new PMDI-VFPP compatibilizer system greatly improved the interfacial adhesion between wood and PP. This PMDI-VFPP compatibilizer system also greatly reduced the water absorption of the resulting wood–PP composites. In this PMDI-VFPP compatibilizer system, PMDI is proposed to function as a wood-binding domain and VFPP to function as a PP-binding domain. PMDI reacted with the amide group in VFPP, thus forming covalent linkages between PMDI and VFPP.