Douglas Gardner | University of Maine (original) (raw)

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Papers by Douglas Gardner

Wood surface properties and adhesion are dominated by its anatomical, chemical, and physical char... more Wood surface properties and adhesion are dominated by its anatomical, chemical, and physical characteristics. Wood can be categorized as a heterogeneous bio-polymer foam composite composed of cellulose, hemicellulose, lignin, and extractives. The differences among wood species as a function of anatomy, chemistry, or physical properties reinforce its description as having a heterogeneous nature. Because of the complex nature of wood structure and the myriad types of wood species, it is difficult to make sweeping generalizations about the surface properties of wood. It should be emphasized that although there are some surface property behaviors that are similar among different wood species, it is usually prudent to learn about the specific species of wood being adhesively bonded.

Carbohydrate Polymers, Dec 1, 2021

Using lignocellulosic nanofibrils as adhesive binders in structural composites is a growing field... more 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. CNFs and lignin containing cellulose nanofibrils (LCNF) were characterized at different length scales using optical, atomic force, and scanning electron microscopy, revealing a complex distribution of sizes, spanning the macroscale to the nanoscale, which are modified unequally by refinement. Strong adhesion was correlated to a decrease in fiber size on the largest length scale and with an increase in relative fibril surface area. Flocculation hampered effective LCNF adhesion, but adding suspension stabilizers improved adhesion to levels comparable to CNF.

Gazi Üniversitesi Orman Fakültesi dergisi, Sep 15, 2018

ACS Applied Polymer Materials

Progress in Additive Manufacturing, 2018

Industrial Crops and Products, 2016

IAWA Journal, 2015

Teak wood (Tectona grandis) as an important forest resource in Indonesia has been processed to wo... more Teak wood (Tectona grandis) as an important forest resource in Indonesia has been processed to wood furniture in large quantities to fulfill an increasing need of both local and international consumers. To satisfy the increasing demand for wood products, teak wood has been supplied from the State forests (Perhutani) and Community teak plantations. Community teak has been harvested at shorter age rotations (7–10 years) than Perhutani teak (40–60 years). This paper discusses the occurrence and characteristics of juvenile wood in Perhutani and Community teak based on density, shrinkage, bending strength (modulus of rupture - MOR, modulus of elasticity - MOE), fiber length, and microfibril angle (MFA). A segmented modeling approach was used to find the juvenile mature transition. Fiber length and MFA appear to be good anatomical indicators of radial increment demarcation between juvenile and mature wood, although maturation radial increment varies slightly between the fiber length and M...

Journal of Thermoplastic Composite Materials, 2019

The viscoelastic behavior of an extruded wood plastic composite (WPC) made from thermally modifie... more The viscoelastic behavior of an extruded wood plastic composite (WPC) made from thermally modified wood under hygrothermal treatment was studied and modeled. Multiple three-point bending creep/recovery tests were carried out using a dynamic mechanical thermal analyzer (DMTA) equipped with a submersible clamp. WPC specimens with a 15-mm span were subjected to two initial applied stresses; 9% and 14% of the flexural strength in 30 min of creep and 30 min of creep recovery under the combined effects of temperature (25°C, 35°C, and 45°C) and water immersion (saltwater (SW) and distilled water). A dry condition WPC control was used to compare the hygrothermal effects with respect to the control conditions. The WPC material in this article exhibited a linear viscoelastic behavior under the effect of temperature, whereas a nonlinear viscoelastic behavior was observed under immersion conditions. A power law model is considered a useful model to describe the creep behavior of WPC specimens w...

Bioresources, Apr 13, 2016

Scientific Reports, Oct 10, 2019

Scientific Reports, Mar 6, 2019

Recyclable cellulose nanofibril (CNF) and lignin-containing cellulose nanofibril (LCNF) coated wo... more Recyclable cellulose nanofibril (CNF) and lignin-containing cellulose nanofibril (LCNF) coated wood flour composites were fabricated using a vacuum-filtration process for food serving applications. The coated cellulose nanofibril composites had excellent mechanical, and oil, and grease barrier properties compared to a commercial container. However, the composites with both LCNF and CNF coating layers had poor performance in wet conditions compared to the commercial container. The addition of 1 wt.% aluminum sulfate (alum) to the CNF and LCNF coating layer significantly improved the water-resistance of the composites. CNF +1% alum coated composites had inferior water resistance and lower mechanical strength in wet conditions compared to the commercial container. However, the LCNF +1% alum coated composites had comparable water resistance and higher wet mechanical properties than the commercial container. The recyclability of the composites was assessed through the disintegration of t...

ACS Sustainable Chemistry & Engineering, 2017

Journal of Thermoplastic Composite Materials, 2019

The hygrothermal effect on the short-term creep behavior of extruded thermally modified wood fibe... more The hygrothermal effect on the short-term creep behavior of extruded thermally modified wood fiber–high-strength styrenic copolymer plastic composites (wood–plastic composites (WPCs)) was investigated on specimens preconditioned for 1 month under water immersion (distilled water (DW) and saltwater (SW)). These specimens were then tested in the same conditions for short-term creep and creep-recovery response using a submersible clamp. The short-term creep tests of WPC specimens (that are immersed in water as a function of different temperatures) have not yet been reported in previous studies. The objective of this study was to determine whether the hygrothermal creep response of WPC material evaluated through water immersion differs from the creep response published in the literature for other environmental exposure conditions. The experiments included measuring 30 min of creep and 30 min of creep recovery on the specimens immersed in SW and DW at two different levels of flexural str...

Resources, Conservation and Recycling, 2022

Wood surface properties and adhesion are dominated by its anatomical, chemical, and physical char... more Wood surface properties and adhesion are dominated by its anatomical, chemical, and physical characteristics. Wood can be categorized as a heterogeneous bio-polymer foam composite composed of cellulose, hemicellulose, lignin, and extractives. The differences among wood species as a function of anatomy, chemistry, or physical properties reinforce its description as having a heterogeneous nature. Because of the complex nature of wood structure and the myriad types of wood species, it is difficult to make sweeping generalizations about the surface properties of wood. It should be emphasized that although there are some surface property behaviors that are similar among different wood species, it is usually prudent to learn about the specific species of wood being adhesively bonded.

Carbohydrate Polymers, Dec 1, 2021

Using lignocellulosic nanofibrils as adhesive binders in structural composites is a growing field... more 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. CNFs and lignin containing cellulose nanofibrils (LCNF) were characterized at different length scales using optical, atomic force, and scanning electron microscopy, revealing a complex distribution of sizes, spanning the macroscale to the nanoscale, which are modified unequally by refinement. Strong adhesion was correlated to a decrease in fiber size on the largest length scale and with an increase in relative fibril surface area. Flocculation hampered effective LCNF adhesion, but adding suspension stabilizers improved adhesion to levels comparable to CNF.

Gazi Üniversitesi Orman Fakültesi dergisi, Sep 15, 2018

ACS Applied Polymer Materials

Progress in Additive Manufacturing, 2018

Industrial Crops and Products, 2016

IAWA Journal, 2015

Teak wood (Tectona grandis) as an important forest resource in Indonesia has been processed to wo... more Teak wood (Tectona grandis) as an important forest resource in Indonesia has been processed to wood furniture in large quantities to fulfill an increasing need of both local and international consumers. To satisfy the increasing demand for wood products, teak wood has been supplied from the State forests (Perhutani) and Community teak plantations. Community teak has been harvested at shorter age rotations (7–10 years) than Perhutani teak (40–60 years). This paper discusses the occurrence and characteristics of juvenile wood in Perhutani and Community teak based on density, shrinkage, bending strength (modulus of rupture - MOR, modulus of elasticity - MOE), fiber length, and microfibril angle (MFA). A segmented modeling approach was used to find the juvenile mature transition. Fiber length and MFA appear to be good anatomical indicators of radial increment demarcation between juvenile and mature wood, although maturation radial increment varies slightly between the fiber length and M...

Journal of Thermoplastic Composite Materials, 2019

The viscoelastic behavior of an extruded wood plastic composite (WPC) made from thermally modifie... more The viscoelastic behavior of an extruded wood plastic composite (WPC) made from thermally modified wood under hygrothermal treatment was studied and modeled. Multiple three-point bending creep/recovery tests were carried out using a dynamic mechanical thermal analyzer (DMTA) equipped with a submersible clamp. WPC specimens with a 15-mm span were subjected to two initial applied stresses; 9% and 14% of the flexural strength in 30 min of creep and 30 min of creep recovery under the combined effects of temperature (25°C, 35°C, and 45°C) and water immersion (saltwater (SW) and distilled water). A dry condition WPC control was used to compare the hygrothermal effects with respect to the control conditions. The WPC material in this article exhibited a linear viscoelastic behavior under the effect of temperature, whereas a nonlinear viscoelastic behavior was observed under immersion conditions. A power law model is considered a useful model to describe the creep behavior of WPC specimens w...

Bioresources, Apr 13, 2016

Scientific Reports, Oct 10, 2019

Scientific Reports, Mar 6, 2019

Recyclable cellulose nanofibril (CNF) and lignin-containing cellulose nanofibril (LCNF) coated wo... more Recyclable cellulose nanofibril (CNF) and lignin-containing cellulose nanofibril (LCNF) coated wood flour composites were fabricated using a vacuum-filtration process for food serving applications. The coated cellulose nanofibril composites had excellent mechanical, and oil, and grease barrier properties compared to a commercial container. However, the composites with both LCNF and CNF coating layers had poor performance in wet conditions compared to the commercial container. The addition of 1 wt.% aluminum sulfate (alum) to the CNF and LCNF coating layer significantly improved the water-resistance of the composites. CNF +1% alum coated composites had inferior water resistance and lower mechanical strength in wet conditions compared to the commercial container. However, the LCNF +1% alum coated composites had comparable water resistance and higher wet mechanical properties than the commercial container. The recyclability of the composites was assessed through the disintegration of t...

ACS Sustainable Chemistry & Engineering, 2017

Journal of Thermoplastic Composite Materials, 2019

The hygrothermal effect on the short-term creep behavior of extruded thermally modified wood fibe... more The hygrothermal effect on the short-term creep behavior of extruded thermally modified wood fiber–high-strength styrenic copolymer plastic composites (wood–plastic composites (WPCs)) was investigated on specimens preconditioned for 1 month under water immersion (distilled water (DW) and saltwater (SW)). These specimens were then tested in the same conditions for short-term creep and creep-recovery response using a submersible clamp. The short-term creep tests of WPC specimens (that are immersed in water as a function of different temperatures) have not yet been reported in previous studies. The objective of this study was to determine whether the hygrothermal creep response of WPC material evaluated through water immersion differs from the creep response published in the literature for other environmental exposure conditions. The experiments included measuring 30 min of creep and 30 min of creep recovery on the specimens immersed in SW and DW at two different levels of flexural str...

Resources, Conservation and Recycling, 2022