Publications by authors named "Douglas J Gardner"

Article Synopsis
  • The study focuses on using an ultrasonic-assisted spray dryer, or nano spray dryer, to create nanometer-sized cellulose particles for pharmaceutical and food applications.
  • While cellulose nanocrystals (CNCs) could be successfully dried to produce nano-SDCNCs, cellulose nanofibrils (CNFs) could not be dried due to their longer lengths.
  • The resulting nano-SDCNCs, when added to a polyvinyl alcohol (PVA) matrix, improved the tensile strength and modulus of the composite film by 22% and 32%, respectively, while maintaining its transparency.
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Article Synopsis
  • Enzyme-treated cellulose nanofibrils (CNFs) were produced from bleached kraft pulp to analyze their energy efficiency during refining and spray-drying operations.
  • The use of endoglucanase enzymes reduced energy consumption and decreased both the degree of polymerization and viscosity in the CNF refining process.
  • When added to a polypropylene (PP) matrix, the enzyme-pretreated SDCNFs improved the strength properties of the composites, confirming their effectiveness compared to previous studies.
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Cellulose nanocrystals (CNCs) are considered a prospective packaging material to partially replace petroleum-based plastics attributed to their renewability, sustainability, biodegradability, and desirable attributes including transparency, oxygen, and oil barrier properties. However, neat CNC films are rigid and too brittle to handle or utilize for packaging applications. Hence different additives, including sorbitol, polyvinyl alcohol (PVA), chitin, and κ-carrageenan (CG) were selected to mix with CNCs for packaging film preparation.

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The use of composite materials has seen many new innovations for a large variety of applications. The area of reinforcement in composites is also rapidly evolving with many new discoveries, including the use of hybrid fibers, sustainable materials, and nanocellulose. In this review, studies on hybrid fiber reinforcement, the use of nanocellulose, the use of nanocellulose in hybrid forms, the use of nanocellulose with other nanomaterials, the applications of these materials, and finally, the challenges and opportunities (including safety issues) of their use are thoroughly discussed.

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A two-step process can turn hardwood into a strong and flexible moldable material.

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Using lignocellulosic nanofibrils as adhesive binders in structural composites is a growing field of interest attributable to their renewability, recyclability, and strength. A fundamental understanding of their adhesion mechanisms is crucial to tailor performance and optimize production costs. These mechanisms were elucidated by studying the morphology dependent adhesion in a model system composed of cellulose nanofibrils (CNFs) at different degrees of refinement and porous paper substrates.

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The production of cellulose nanofibrils (CNFs) continues to receive considerable attention because of their desirable material characteristics for a variety of consumer applications. There are, however, challenges that remain in transitioning CNFs from research to widespread adoption in the industrial sectors, including production cost and material performance. This Review covers CNFs produced from nonconventional fibrillation methods as a potential alternative solution.

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Driven by the motive of minimizing the transportation costs of raw materials to manufacture wood-plastic composites (WPCs), Part I and the current Part II of this paper series explore the utilization of an alternative wood feedstock, i.e., pellets.

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Article Synopsis
  • This paper examines the use of the Padé-Laplace (PL) method for deconvoluting multi-exponential functions in polymer stress relaxation, highlighting issues with ill-conditioned systems of equations.
  • Increasing the level of Padé approximants leads to rapidly growing condition numbers in matrices, making it challenging to achieve stable separation of exponential modes.
  • The study proposes a regularization approach through system reconstruction and singular value decomposition (SVD), which enhances the PL method's ability to effectively deconvolute even under suboptimal input parameters.
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Article Synopsis
  • The U.S. produces significant secondary residues from wood processing facilities, which can be turned into wood flour for wood-plastic composites (WPCs).
  • High transportation costs due to low bulk density of wood flour lead to increased expenses for WPC manufacturers, as flour is heavier to transport than pellets.
  • A study of residues from four wood species in Maine revealed that red maple wood flour had the best properties, including higher bulk density and lower moisture content, making it a more efficient raw material for WPCs.
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Cost-effective, eco-friendly, and oil and grease-resistant food serving containers were made from wood flour with cellulose nanofibrils (CNF) or lignin-containing cellulose nanofibrils (LCNF) coating layers on the surface and in the bulk. The multi-layer wet-on-wet cellulose nanofiber composites were developed using a vacuum filtration process. All composites showed excellent oil/grease resistivity according to the "kit" test passing #12, the highest possible.

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In nature, cellulose nanofibers form hierarchical structures across multiple length scales to achieve high-performance properties and different functionalities. Cellulose nanofibers, which are separated from plants or synthesized biologically, are being extensively investigated and processed into different materials owing to their good properties. The alignment of cellulose nanofibers is reported to significantly influence the performance of cellulose nanofiber-based materials.

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Advanced templating techniques have enabled delicate control of both nano- and microscale structures and have helped thrust functional materials into the forefront of society. Cellulose nanomaterials are derived from natural polymers and show promise as a templating source for advanced materials. Use of cellulose nanomaterials in templating combines nanoscale property control with sustainability, an attribute often lacking in other templating techniques.

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Article Synopsis
  • Modifying cellulose nanofibrils (CNFs) with polymer functional groups in a water-based system is challenging due to limited accessible surface interactions.
  • A new scheme involves functionalizing CNFs with a methacrylate group followed by grafting-through polymerization, achieving up to 45 wt% polymer attachment with various types of (meth)acrylates.
  • The effectiveness of this method was validated through techniques like Soxhlet extraction and IR spectroscopy, revealing that high polymer modification levels do not significantly alter the overall morphology of the CNFs.
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Poly(lactic acid) (PLA) was used in an effort to enhance the mechanical properties of poly(hydroxybutyrate) (PHB) and the blends were reinforced with cellulose nanofibrils (CNF). The conventional and dynamic mechanical, morphological, thermal and rheological properties of the obtained composite blends were determined. The results showed that the mechanical properties of neat PHB noticeably increased attributable to the good interaction between the biopolymers and CNF from the scanning electron microscopy (SEM) characterization.

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Article Synopsis
  • The review explores the use of wood and lignocellulosic materials as sustainable additives in 3D printing composites, highlighting their potential to improve material properties while offering an eco-friendly alternative to traditional fillers.
  • Previous studies primarily focused on the introduction of natural fillers; this review aims to provide a comprehensive understanding of their current applications and advancements in materials extrusion additive manufacturing.
  • It addresses challenges in large-scale 3D printing with these materials and offers insights on how to overcome these issues moving forward.
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The use of wood plastic composite lumber as a structural member material in marine applications is challenging due to the tendency of wood plastic composites (WPCs) to creep and absorb water. A novel patent-pending WPC formulation that combines a thermally modified wood flour (as a cellulosic material) and a high strength styrenic copolymer (high impact polystyrene and styrene maleic anhydride) have been developed with advantageous viscoelastic properties (low initial creep compliance and creep rate) compared with the conventional WPCs. In this study, the creep behavior of the WPC and high-density polyethylene (HDPE) lumber in flexure was characterized and compared.

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Based on previous research, a novel wood-plastic composite (WPC) lumber has shown potential to replace high-density polyethylene (HDPE) lumber in the construction of aquacultural geodesic spherical cage structures. Six HDPE and six WPC assemblies, which are representative of typical full-size cage dimensions, were fabricated by bolting pairs of triangular panel components made with connected struts. Half of the panel assemblies had a plastic-coated steel wire mesh to simulate the actual restraint in field applications of the cages.

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The economic viability of the biofuel industry could be improved by adding a high-value revenue stream for biomass supply chains: bioderived composites for the rapidly expanding large-scale additive manufacturing industry (i.e., 3D printing).

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Article Synopsis
  • The study focuses on using cellulose nanofibrils (CNF) as an adhesive in making wood-based composites, emphasizing the need for effective water removal during processing.
  • The dewatering behavior was examined through various tests, and it was found that the size of wood particles significantly affects how quickly water can be removed from the mixture.
  • Results indicated that most of the water is removed in the initial stages, as the contact between CNF and wood particles rapidly enhances the dewatering rate.
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Poly (vinyl alcohol) (PVA) and cellulose nanocrystals (CNC) random composite mats were prepared using the electrospinning method. PVA/CNC mats were reinforced with weight concentrations of 0, 20 and 50% CNC (/) relative to PVA. Scanning electron microscopy was used to measure the fiber diameter, which ranged from 377 to 416 nm.

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Novel hybrid panel composites based on wood, fungal mycelium, and cellulose nanofibrils (CNF) were developed and investigated in the present study. In one set of experiments, mycelium was grown on softwood particles to produce mycelium-modified wood which was then hybridized with various levels of CNF as binder. The other set of experiments were conducted on unmodified wood particles mixed with CNF and pure mycelium tissue.

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Cellulose nanofibrils (CNF) were spun into filaments directly from suspension without the aid of solvents. The influence of starting material properties and drying temperature on the properties of filaments produced from three different CNF suspensions was studied. Refiner-produced CNF was ground using a microgrinder at grinding times of 50 and 100 minutes.

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Article Synopsis
  • A novel laminate system using cellulose nanofibrils (CNF) as a binding agent for paper sheets was developed and tested for mechanical properties.
  • Bonding was confirmed through peeling tests and laminates were assessed under various conditions, showing impressive strength and elasticity, comparable to existing composite materials.
  • Additionally, properties like water absorption and thickness swelling were measured, with the swelling managed by a cross-linking additive.
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