Despite the recent advances in protein-based adhesives, achieving strong adhesion and mold resist... more Despite the recent advances in protein-based adhesives, achieving strong adhesion and mold resistance in wet environment is challenging. Herein, a facile fabrication technology of preparing tough bio-adhesive by incorporating soybean meal and blood meal is presented. Inspired by the marine mussel byssi and brown algae, metal coordination was introduced into a loosely bound protein system to construct multiple chemical cross-linking networks. Mixed alkali-modified blood meal (mBM) was mixed with soybean meal, then 1,6-hexane dioldiglycidyl ether (HDE) and zinc ion were introduced to fabricate soybean meal and blood meal-based adhesives. The attained adhesives exhibited good thermal stability, water resistance (the wet shear strength is 1.1 MPa), and mold resistance, with appropriate solid content (34.3%) and relatively low moisture uptake (11.9%). These outstanding performances would be attributed to the reaction of 1,6-hexane dioldiglycidyl ether with protein to form a preliminary cross-linking network; subsequently, the coordination of zinc ions with amino or carboxyl strengthened and toughened the adhesive. Finally, the calcium ions gelled the adhesives, providing cohesion force and making the network structure more compact. This study realized the value-added utilization of protein co-products and developed a new eco-friendly bio-based adhesive.
Wood densification can improve the strength of low density wood species and extend wood product a... more Wood densification can improve the strength of low density wood species and extend wood product applications. To enhance the wood compressive quality, chemical pretreatments for pristine wood have widely been used. Densified Abies wood was fabricated by combining NaOH/Na 2 SO 3 solution treatment, hot-pressing and post mechanical fixation. The appearance, color, chemical composition, and physiology and mechanical properties before and after the densification treatment were examined by the colorimeter, FTIR and mechanical testing machine, respectively. Surface color of Abies wood was changed obviously after the densification. The values of brightness L* and b* decreased but the value of a* showed a slight increase in the densified wood. FTIR results confirmed that the color changes can be explained by the degradation of hemicellulose and lignin in wood cell walls and migration of extractives during the densification process. Sufficient removal of wood polymers resulted in the average compression ratio of about 80% in the radial direction of the natural wood. The density of densified wood increased with the wood thickness up to 1.227 g cm −1 , accounting for a 169% increase compared to that of the pristine wood. Modulus of rupture (MOR) and modulus of elasticity (MOE) in the thickness direction of densified wood also markedly enhanced. Degradation of polymers in wood cell walls also was reconfirmed by the difference of fracture interface. All the results suggested that the densified softwood can be easily fabricated using the proposed method and the new densified softwood can be appropriately used as interior decoration materials.
This research is intended to expand information on fiber characteristics for better understanding... more This research is intended to expand information on fiber characteristics for better understanding their complexity and potential in industrial use. Tensile properties of four types of individual cellulosic fibers, bamboo, kenaf, Chinese fir, and ramie, were measured by a custom-designed microtensile tester. Load-displacement curves for most individual fibers were found to be linear until failure. Average values of at least 30 individual fibers of bamboo, kenaf,
In this study, a microwave oven with a frequency of 2450 MHz was used for the surface modificatio... more In this study, a microwave oven with a frequency of 2450 MHz was used for the surface modification of rubber particles. The samples were treated with five different output powers (160, 320, 480, 640, and 800 W) for six exposure times (1, 2, 3, 4, 5, and 6 min). The influence of the microwave treatment on rubber characteristics was analyzed by Fourier transform infrared spectroscopy. The woodrubber composites were fabricated using 70% poplar particles and 30% rubber particles. Four regression equations, ie radiation time and power as functions of modulus of rupture, modulus of elasticity, internal bond, and thickness swelling, were developed and a nonlinear programing model was derived to obtain the optimum panel properties. The results from contact angle measurements and microscopic analysis indicated that the surface characteristics were changed after the microwave treatment, improving the mechanical properties of the wood-rubber composites.
The objective of this study was to investigate the deformation behavior and damage model of bambo... more The objective of this study was to investigate the deformation behavior and damage model of bamboo bundle corrugated laminated composites under low velocity impact loading. The influence of different stacking sequences, i.e., bamboo bundle parallel to the corrugated waves (type I), cross-ply (type II), and perpendicular to the waves (type III), in laminates was studied in regard to impact loading. A shape parameter, K, was developed to quantify the effect of corrugation on impact response. The results of this study indicated that the type I composites displayed the optimum impact performance, followed by types II and III. The total energy absorbed by the type I laminates was 1.3 and 2.2 times as much as types II and III. The values of peak load were type I > type II > type III. The composites deformed and failed in different manners under low velocity impact loading: material failure, delamination and fiber tensile fracture, and structural collapse were the main modes of failure for type I, II, and III, respectively. The effect of the corrugated shape on impact properties of composites was positive for type I, but negative for type II composites.
In the quest of materials that can tolerate extreme environments (i.e., aerospace, polar regions ... more In the quest of materials that can tolerate extreme environments (i.e., aerospace, polar regions of earth), facile design of self-healing, high fatigue-resistant and multifunctional nanocomposite materials with excellent ultralow temperature toughness, especially by utilizing inexpensive and sustainable bioresources is still currently challengeable. In current study, we present a material that displays remarkable ultralow temperature toughness, shows excellent toughness (107.3 MJ•m-3) at − 196°C and maintains high mechanical strength in highly humid environments. This material is a spider silk-inspired, poly(vinyl alcohol) (PVA)-based, autonomous room temperature self-healable nanocomposite by complexation of boron nitride (BN), quantum dots (QDs) and soybean protein isolate grafted lignin (SPIlignin). The fabricated material, namely PVA-BN-QDs-SPI-lignin, simultaneously exhibits outstanding tensile strength (53.3 MPa), toughness (182.8 MJ•m-3), fatigue-resistance as well as antiultraviolet and uorescent properties and sets an impressive new record of folding-failure (900 000 times) and toughness, which are 10.6 to 45.7 times higher than other graphene-based nanocomposites. It can be impressively self-healed within only 2 minutes. Of particular interest is its facile, green, mild and inexpensive preparation method that can be easily scale up. It is believed that this work, beginning with abundant biodegradable resources, opens the door to develop biobased multifunctional materials in practical applications, such as exible wearable materials.
The investigation is on comparative life-cycle assessments of three fiber-reinforced sheet moldin... more The investigation is on comparative life-cycle assessments of three fiber-reinforced sheet molding compound (SMC) made from kenaf fiber, glass fiber and soy-based resin, respectively. SMCs for automotive applications are typically made of unsaturated polyesters and glass fibers. Using kenaf fiber and soy-based resin to partially replace the glass fiber and polyester resin is driven by their potential environmental benefits. A soy-based resin, maleatedacrylatedepoxidized soy oil (MAESO), was synthesized from refined soybean oil. SMC1 composite was made from kenaf fiber and polyester resin while SMC2 composite fromkenaf fiber and a resin blend of 20 % MASEO and 80% unsaturated polyester. SMC1 and SMC2 have both achieved substantial physical and mechanical properties, but were not yet comparable to a glass fiber reinforced polyester SMC in strength property (Springer, 1983, J. Reinforced Plastics Composites, 2(2):70-89). Thus, functional unit was defined as a mass to achieve the equal stiffness and stability when used to make interior parts for automobiles. The life-cycle assessments were conducted for three composites: SMC1, SMC2 and the glass fiber reinforced SMC. The materials and energy input/output of producing one functional unit of three composites were collected from lab experiments and literature. The key environmental measures were computed with SimaPro software. The results show that both kenaf fiber reinforced SMCs perform better than glass fiber SMC in every environmental category. The global warming potential of kenaf fiber SMC (SMC1) and kenaf soy resin based SMC (SMC2) were only about 45% and 58% of that for glass fiber SMC, respectively. This preliminary result has demonstrated that using soy-based resin and natural fiber for SMC would have a great ecological benefit.
This research investigated the use of reclaimed rubber (RR) from waste tires to partially replace... more This research investigated the use of reclaimed rubber (RR) from waste tires to partially replace the rubber compound (RC) when making wood fiber-rubber composites (WRCs). Ninety panels of WRC containing RR were manufactured with RR contents of 0% to 40%, mixing times of 6 min to 14 min, and vulcanizing temperatures of 150 °C to 170 °C. There were three steps, which were the fiber-rubber mixing, tabletting, and vulcanization molding processes. Four regression equations for the tensile strength, elongation at break, hardness, and rebound resilience as functions of the RR content, mixing time, and vulcanizing temperature were derived, and a nonlinear programming model was developed to obtain the optimum panel properties. It was found that when the RR content was within 20%, the wood fibers were well encapsulated and embedded in the RC/RR blends, and the processability of the WRCs were improved by adding RR. The incorporation of RR into the WRCs increased the average tensile strength and hardness by 33.9% and 2.3%, respectively, while the swelling ratio in toluene and 24-h water absorption were reduced by 13% and 42%, respectively.
The effects of using sodium dodecyl sulfate (SDS) and a modified polyacrylic acid solution (MPA) ... more The effects of using sodium dodecyl sulfate (SDS) and a modified polyacrylic acid solution (MPA) on a soybean meal adhesive were investigated. Three-ply plywood specimens were fabricated to measure the water resistance of the adhesive (three-cycle soak test). The viscosity and solid content of the adhesive were measured. The crosssection and functional groups of the cured adhesive were evaluated using scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. The results showed that using SDS improved the water resistance of the soybean meal adhesive by 30%. After incorporating MPA, the water resistance of the soybean meal/SDS/MPA adhesive was further improved by 60%, the viscosity of the adhesive was reduced by 81%, and the solid content of the adhesive increased by 15%. The plywood bonded by the soybean meal/SDS/MPA adhesive met the interior plywood requirements. SEM results showed no holes and cracks on the cross-section of the cured soybean meal/SDS/ MPA adhesive. FTIR analysis indicated that more peptide linkages were formed in the cured adhesive as MPA was incorporated.
Soybean meal (SM)-based adhesive exhibited a great potential to replace petroleum-derived ones to... more Soybean meal (SM)-based adhesive exhibited a great potential to replace petroleum-derived ones to alleviate the energy crisis and eliminate carcinogenic formaldehyde. However, the bad water resistance (caused by low crosslinking density) and inherent brittleness of SM adhesive severely hindered its application. However, improving crosslinking density is generally accompanied by a toughness reduction of the adhesive. Herein, we developed a flexible long-chain starch with a hyper-branched structure (HD), and incorporated it with SM and a crosslinking agent to prepare a novel SM adhesive. Results showed that this adhesive exhibited both excellent water resistance and enhanced toughness. The wet bond strength of plywood fabricated using this adhesive was 354.5% higher than that of SM adhesive. These achievements are because introducing HD with hyper-branched groups enhanced crosslinking density, while HD's flexible long-chain structure improved toughness of the adhesive. This HD can promote the development of tough and hydrophobic bio-based composites.
In this study, a novel ultrasonic non-destructive and non-invasive elastography method was introd... more In this study, a novel ultrasonic non-destructive and non-invasive elastography method was introduced and demonstrated to evaluate the mechanical properties of fused deposition modeling 3D printed objects using two-dimensional dynamical elasticity mapping. Based on the recently investigated dynamic bulk modulus and effective density imaging technique, an angle-dependent dynamic shear modulus measurement was performed to extract the dynamic Young's modulus distribution of the FDM structures. The elastographic image analysis demonstrated the presence of anisotropic dynamic shear modulus and dynamic Young's modulus existing in the fused deposition modeling 3D printed objects. The non-destructive method also differentiated samples with high contrast property zones from that of low contrast property regions. The angle-dependent elasticity contrast behavior from the ultrasonic method was compared with conventional and static tensile tests characterization. A good correlation between the nondestructive technique and the tensile test measurements was observed.
The focus of this report was to understand the tensile properties and dynamic mechanical properti... more The focus of this report was to understand the tensile properties and dynamic mechanical properties of bamboo powder (BP) reinforced polylactic acid (PLA) composite filaments which were treated with nano calcium carbonate (CaCO 3), cellulose nanofibers (CNF), and micro-crystalline cellulose (MCC) using impregnation modification technology. The storage modulus (E') of nano CaCO 3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments increased compared with BP/PLA composite filaments before the glass transition temperature T g. When the temperature was above T g , the reinforcement effect of nano CaCO 3 , MCC, and CNF gradually became less apparent. The loss modulus (E") and loss factor (tan δ max) of the nano CaCO 3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments was higher than that of BP/PLA composite filaments produced by the "one-step" method. The tensile strength (TS) results showed a similar trend. Compared with the control samples, the TS of nano CaCO 3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments produced by the "one-step" method (and the "two-step" method) increased by 40.33% (and 10.10%), 32.35% (and −8.61%), and 12.32% (and −12.85%), respectively. The TS of nano CaCO 3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments produced by the "one-step" method was slightly higher than those produced by the "two-step" method. The elongation at break (EAB) of BP/PLA composite filaments was higher than that of BP/PLA samples treated with nano CaCO 3 , MCC, or CNF. The PLA and modified BP were readily accessible through a simple mixing process. The rheological investigation of such mixtures showed that nano CaCO 3 , CNF, and MCC have different effects on the processability and rheological properties of composites.
The soy protein isolate (SPI), sodium dodecylbenzenesulfonate (SDBS) and pentaerythritol glycidyl... more The soy protein isolate (SPI), sodium dodecylbenzenesulfonate (SDBS) and pentaerythritol glycidyl ether (PEGE) were used to make biodegradable films in this study. Unlike the usual method that adding sodium hydroxide (NaOH) during the SPI-based film casting, SDBS was used as a surfactant playing the similar role as NaOH. Since NaOH is a chemical with corrosiveness and toxicity, the replacing of NaOH by SDBS might reduce the hazard threat during the utilization of SPI-based films in food packing application. Furthermore, the presentation of SDBS helped dispersing the hydrophobic PEGE into the hydrophilic SPI. PEGE is a crosslinking agent with multiple reactive epoxy groups. The chemical structures and micro morphologies of the fabricated films were investigated by means of FTIR, XRD, and SEM. The thermal stabilities of the films were examined by means of the thermo-gravimetric analysis. After the chemical crosslinking, the ultimate tensile strength of the film was significantly increased, meanwhile, the water absorption was dramatically decreased. It was concluded that the SPI-based film containing 4% PEGE achieved the optimal performance.
The objective of this study was to investigate the deformation behavior of bamboo bundle laminate... more The objective of this study was to investigate the deformation behavior of bamboo bundle laminated veneer lumber (BLVL) manufactured with veneer preprocessing densification technology under low velocity impact loading. The influence of different preprocessing temperatures, times, and stacking sequences was studied with respect to impact loading. Laminates with bamboo bundles parallel to the length direction were labeled as type I, and cross-ply was labeled as type II. The results indicated that delamination and fiber breakage were the main damage models for BLVL made with veneer preprocessing densification technology, and its impact performance under a veneer prepressing temperature of 90°C and a time of 10 min was fairly comparable to that of BLVL without preprocessing densification. The impact index decreased as the densification temperature increased. The impact properties for type II were better than that of type I. The curve characteristic of impact deflection vs. time presented a linear trend, while the curve of impact velocity first decreased and then tended to level off as time elapsed.
The objective of this research was to evaluate the properties of the chemically retted kenaf bast... more The objective of this research was to evaluate the properties of the chemically retted kenaf bast fiber impregnated with the inorganic nanoparticles. High quality kenaf bast fibers were obtained from a chemical retting process. An in situ inorganic nanoparticle impregnation (INI) process was used to introduce the CaCO 3 nanoparticles into the retted kenaf bast fibers. It was found that some of the lignin-based components in the retted fibers were further removed during the INI treatment. From the characterization results, the inorganic nanoparticles CaCO 3 , with different shapes and sizes, appeared at the surface of the impregnated fiber after treatment. Heterogeneous CaCO 3 nanoparticle distribution was observed on the INI treated fibers. The CaCO 3 contents were different at different locations along the impregnated fiber. The presence of CaCO 3 inorganic nanoparticles at the fiber surface increased the root mean square (RMS) surface roughness by 5.8% and decreased the hydrophilic nature of the retted fibers, evidenced by a 59.4% decrease in adhesion force between the fiber and hydrophilic AFM tip. In addition, the impregnation of CaCO 3 dramatically increased the Young's modulus of the fiber by 344%.
Ongoing research into chemically treating southern hardwoods for producing structural composite l... more Ongoing research into chemically treating southern hardwoods for producing structural composite lumber suggests that some improvements may be imparted by modifying the wood. How chemical treatment(s) affect modified wood durability, particularly resistance to Reticulitermes flavipes, was the objective of this study. Water-saturated samples of yellow-poplar, sweetgum, and red oak were heated at 150 C for 30 min in two solutions: water and 1.0% NaOH; controls were also included. Samples were subjected to the AWPA E1-09 no-choice termite test in which mass loss from R. flavipes was determined. The species and treatments independently and significantly affected the mass loss. Yellow-poplar, which had the lowest specific gravity, averaged significantly greater mass loss than sweetgum and red oak for all three exposures. All species treated in water or NaOH showed a higher degree of termite degradation as compared with the controls.
Differing from the hot-pressing method in the manufacturing of traditional wood-rubber composites... more Differing from the hot-pressing method in the manufacturing of traditional wood-rubber composites (WRCs), this study was aimed at fabricating WRCs using rubber processing to improve water resistance and mechanical properties. Three steps were used to make WRCs, namely, fiber-rubber mixing, tabletting, and the vulcanization molding process. Ninety-six WRC panels were made with wood fiber contents of 0%-50% at rotor rotational speeds of 15-45 rpm and filled coefficients of 0.55-0.75. Four regression equations, i.e., the tensile strength (Ts), elongation at break (Eb), hardness (Ha) and rebound resilience (Rr) as functions of fiber contents, rotational speed and filled coefficient, were derived and a nonlinear programming model were developed to obtain the optimum composite properties. Although the Ts, Eb and Rr of the panels were reduced, Ha was considerably increased by 17%-58% because of the wood fiber addition. Scanning electron microscope images indicated that fibers were well embedded in rubber matrix. The 24 h water absorption was only 1%-3%, which was much lower than commercial wood-based composites.
This paper describes the bending creep behavior of two types of bamboo-based products, bamboo-lam... more This paper describes the bending creep behavior of two types of bamboo-based products, bamboo-laminated veneer lumber (BLVL), and glued-laminated bamboo (GLB, also called Bamboo Glulam) at different stress levels for half a year and recovery for the same time. It was found that the stress level of BLVL was more sensitive on creep property than that of GLB; the creep resistance of GLB was worse than that of BLVL in the stress levels of 30-50%; the instantaneous recovery ratio (elastic recovery to elastic creep) decreased with an increase of the stress levels, while the residual ratio (residual deformation corresponded to the total creep deflections) increased with an increase of stress levels for all specimens; Burgers model fit creep data very well for both bamboo-based products, while the recovery Weibull equation does not fit recovery data well for GLB.
The objective of this study was to evaluate the uniformity of density distribution for Bamboo-bun... more The objective of this study was to evaluate the uniformity of density distribution for Bamboo-bundle Laminated Veneer Lumber (BLVL) and its relationship to the stability of mechanical performance. A novel assembly style called one-piece veneer formation technology was developed to enhance the density uniformity, and four different density levels for BLVL were examined by X-ray scanning. The results indicated that the homogeneity of density, the stability of mechanical performance, and the mechanical properties for BLVL could be effectively improved by assembling the bamboo bundles into layers and then combining the layers to make the lumber. The density uniformity in width and thickness directions increased with increasing target density. A negatively linear correlation between density and Coefficient of Variation (COV) of MOR and shearing strength was observed. Partial correlation analysis revealed that when controlling for the variability of density, the linear relationship between density and the COV of MOR became insignificant, and the degree of linear correlation between density and the COV of shearing strength decreased.
Despite the recent advances in protein-based adhesives, achieving strong adhesion and mold resist... more Despite the recent advances in protein-based adhesives, achieving strong adhesion and mold resistance in wet environment is challenging. Herein, a facile fabrication technology of preparing tough bio-adhesive by incorporating soybean meal and blood meal is presented. Inspired by the marine mussel byssi and brown algae, metal coordination was introduced into a loosely bound protein system to construct multiple chemical cross-linking networks. Mixed alkali-modified blood meal (mBM) was mixed with soybean meal, then 1,6-hexane dioldiglycidyl ether (HDE) and zinc ion were introduced to fabricate soybean meal and blood meal-based adhesives. The attained adhesives exhibited good thermal stability, water resistance (the wet shear strength is 1.1 MPa), and mold resistance, with appropriate solid content (34.3%) and relatively low moisture uptake (11.9%). These outstanding performances would be attributed to the reaction of 1,6-hexane dioldiglycidyl ether with protein to form a preliminary cross-linking network; subsequently, the coordination of zinc ions with amino or carboxyl strengthened and toughened the adhesive. Finally, the calcium ions gelled the adhesives, providing cohesion force and making the network structure more compact. This study realized the value-added utilization of protein co-products and developed a new eco-friendly bio-based adhesive.
Wood densification can improve the strength of low density wood species and extend wood product a... more Wood densification can improve the strength of low density wood species and extend wood product applications. To enhance the wood compressive quality, chemical pretreatments for pristine wood have widely been used. Densified Abies wood was fabricated by combining NaOH/Na 2 SO 3 solution treatment, hot-pressing and post mechanical fixation. The appearance, color, chemical composition, and physiology and mechanical properties before and after the densification treatment were examined by the colorimeter, FTIR and mechanical testing machine, respectively. Surface color of Abies wood was changed obviously after the densification. The values of brightness L* and b* decreased but the value of a* showed a slight increase in the densified wood. FTIR results confirmed that the color changes can be explained by the degradation of hemicellulose and lignin in wood cell walls and migration of extractives during the densification process. Sufficient removal of wood polymers resulted in the average compression ratio of about 80% in the radial direction of the natural wood. The density of densified wood increased with the wood thickness up to 1.227 g cm −1 , accounting for a 169% increase compared to that of the pristine wood. Modulus of rupture (MOR) and modulus of elasticity (MOE) in the thickness direction of densified wood also markedly enhanced. Degradation of polymers in wood cell walls also was reconfirmed by the difference of fracture interface. All the results suggested that the densified softwood can be easily fabricated using the proposed method and the new densified softwood can be appropriately used as interior decoration materials.
This research is intended to expand information on fiber characteristics for better understanding... more This research is intended to expand information on fiber characteristics for better understanding their complexity and potential in industrial use. Tensile properties of four types of individual cellulosic fibers, bamboo, kenaf, Chinese fir, and ramie, were measured by a custom-designed microtensile tester. Load-displacement curves for most individual fibers were found to be linear until failure. Average values of at least 30 individual fibers of bamboo, kenaf,
In this study, a microwave oven with a frequency of 2450 MHz was used for the surface modificatio... more In this study, a microwave oven with a frequency of 2450 MHz was used for the surface modification of rubber particles. The samples were treated with five different output powers (160, 320, 480, 640, and 800 W) for six exposure times (1, 2, 3, 4, 5, and 6 min). The influence of the microwave treatment on rubber characteristics was analyzed by Fourier transform infrared spectroscopy. The woodrubber composites were fabricated using 70% poplar particles and 30% rubber particles. Four regression equations, ie radiation time and power as functions of modulus of rupture, modulus of elasticity, internal bond, and thickness swelling, were developed and a nonlinear programing model was derived to obtain the optimum panel properties. The results from contact angle measurements and microscopic analysis indicated that the surface characteristics were changed after the microwave treatment, improving the mechanical properties of the wood-rubber composites.
The objective of this study was to investigate the deformation behavior and damage model of bambo... more The objective of this study was to investigate the deformation behavior and damage model of bamboo bundle corrugated laminated composites under low velocity impact loading. The influence of different stacking sequences, i.e., bamboo bundle parallel to the corrugated waves (type I), cross-ply (type II), and perpendicular to the waves (type III), in laminates was studied in regard to impact loading. A shape parameter, K, was developed to quantify the effect of corrugation on impact response. The results of this study indicated that the type I composites displayed the optimum impact performance, followed by types II and III. The total energy absorbed by the type I laminates was 1.3 and 2.2 times as much as types II and III. The values of peak load were type I > type II > type III. The composites deformed and failed in different manners under low velocity impact loading: material failure, delamination and fiber tensile fracture, and structural collapse were the main modes of failure for type I, II, and III, respectively. The effect of the corrugated shape on impact properties of composites was positive for type I, but negative for type II composites.
In the quest of materials that can tolerate extreme environments (i.e., aerospace, polar regions ... more In the quest of materials that can tolerate extreme environments (i.e., aerospace, polar regions of earth), facile design of self-healing, high fatigue-resistant and multifunctional nanocomposite materials with excellent ultralow temperature toughness, especially by utilizing inexpensive and sustainable bioresources is still currently challengeable. In current study, we present a material that displays remarkable ultralow temperature toughness, shows excellent toughness (107.3 MJ•m-3) at − 196°C and maintains high mechanical strength in highly humid environments. This material is a spider silk-inspired, poly(vinyl alcohol) (PVA)-based, autonomous room temperature self-healable nanocomposite by complexation of boron nitride (BN), quantum dots (QDs) and soybean protein isolate grafted lignin (SPIlignin). The fabricated material, namely PVA-BN-QDs-SPI-lignin, simultaneously exhibits outstanding tensile strength (53.3 MPa), toughness (182.8 MJ•m-3), fatigue-resistance as well as antiultraviolet and uorescent properties and sets an impressive new record of folding-failure (900 000 times) and toughness, which are 10.6 to 45.7 times higher than other graphene-based nanocomposites. It can be impressively self-healed within only 2 minutes. Of particular interest is its facile, green, mild and inexpensive preparation method that can be easily scale up. It is believed that this work, beginning with abundant biodegradable resources, opens the door to develop biobased multifunctional materials in practical applications, such as exible wearable materials.
The investigation is on comparative life-cycle assessments of three fiber-reinforced sheet moldin... more The investigation is on comparative life-cycle assessments of three fiber-reinforced sheet molding compound (SMC) made from kenaf fiber, glass fiber and soy-based resin, respectively. SMCs for automotive applications are typically made of unsaturated polyesters and glass fibers. Using kenaf fiber and soy-based resin to partially replace the glass fiber and polyester resin is driven by their potential environmental benefits. A soy-based resin, maleatedacrylatedepoxidized soy oil (MAESO), was synthesized from refined soybean oil. SMC1 composite was made from kenaf fiber and polyester resin while SMC2 composite fromkenaf fiber and a resin blend of 20 % MASEO and 80% unsaturated polyester. SMC1 and SMC2 have both achieved substantial physical and mechanical properties, but were not yet comparable to a glass fiber reinforced polyester SMC in strength property (Springer, 1983, J. Reinforced Plastics Composites, 2(2):70-89). Thus, functional unit was defined as a mass to achieve the equal stiffness and stability when used to make interior parts for automobiles. The life-cycle assessments were conducted for three composites: SMC1, SMC2 and the glass fiber reinforced SMC. The materials and energy input/output of producing one functional unit of three composites were collected from lab experiments and literature. The key environmental measures were computed with SimaPro software. The results show that both kenaf fiber reinforced SMCs perform better than glass fiber SMC in every environmental category. The global warming potential of kenaf fiber SMC (SMC1) and kenaf soy resin based SMC (SMC2) were only about 45% and 58% of that for glass fiber SMC, respectively. This preliminary result has demonstrated that using soy-based resin and natural fiber for SMC would have a great ecological benefit.
This research investigated the use of reclaimed rubber (RR) from waste tires to partially replace... more This research investigated the use of reclaimed rubber (RR) from waste tires to partially replace the rubber compound (RC) when making wood fiber-rubber composites (WRCs). Ninety panels of WRC containing RR were manufactured with RR contents of 0% to 40%, mixing times of 6 min to 14 min, and vulcanizing temperatures of 150 °C to 170 °C. There were three steps, which were the fiber-rubber mixing, tabletting, and vulcanization molding processes. Four regression equations for the tensile strength, elongation at break, hardness, and rebound resilience as functions of the RR content, mixing time, and vulcanizing temperature were derived, and a nonlinear programming model was developed to obtain the optimum panel properties. It was found that when the RR content was within 20%, the wood fibers were well encapsulated and embedded in the RC/RR blends, and the processability of the WRCs were improved by adding RR. The incorporation of RR into the WRCs increased the average tensile strength and hardness by 33.9% and 2.3%, respectively, while the swelling ratio in toluene and 24-h water absorption were reduced by 13% and 42%, respectively.
The effects of using sodium dodecyl sulfate (SDS) and a modified polyacrylic acid solution (MPA) ... more The effects of using sodium dodecyl sulfate (SDS) and a modified polyacrylic acid solution (MPA) on a soybean meal adhesive were investigated. Three-ply plywood specimens were fabricated to measure the water resistance of the adhesive (three-cycle soak test). The viscosity and solid content of the adhesive were measured. The crosssection and functional groups of the cured adhesive were evaluated using scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. The results showed that using SDS improved the water resistance of the soybean meal adhesive by 30%. After incorporating MPA, the water resistance of the soybean meal/SDS/MPA adhesive was further improved by 60%, the viscosity of the adhesive was reduced by 81%, and the solid content of the adhesive increased by 15%. The plywood bonded by the soybean meal/SDS/MPA adhesive met the interior plywood requirements. SEM results showed no holes and cracks on the cross-section of the cured soybean meal/SDS/ MPA adhesive. FTIR analysis indicated that more peptide linkages were formed in the cured adhesive as MPA was incorporated.
Soybean meal (SM)-based adhesive exhibited a great potential to replace petroleum-derived ones to... more Soybean meal (SM)-based adhesive exhibited a great potential to replace petroleum-derived ones to alleviate the energy crisis and eliminate carcinogenic formaldehyde. However, the bad water resistance (caused by low crosslinking density) and inherent brittleness of SM adhesive severely hindered its application. However, improving crosslinking density is generally accompanied by a toughness reduction of the adhesive. Herein, we developed a flexible long-chain starch with a hyper-branched structure (HD), and incorporated it with SM and a crosslinking agent to prepare a novel SM adhesive. Results showed that this adhesive exhibited both excellent water resistance and enhanced toughness. The wet bond strength of plywood fabricated using this adhesive was 354.5% higher than that of SM adhesive. These achievements are because introducing HD with hyper-branched groups enhanced crosslinking density, while HD's flexible long-chain structure improved toughness of the adhesive. This HD can promote the development of tough and hydrophobic bio-based composites.
In this study, a novel ultrasonic non-destructive and non-invasive elastography method was introd... more In this study, a novel ultrasonic non-destructive and non-invasive elastography method was introduced and demonstrated to evaluate the mechanical properties of fused deposition modeling 3D printed objects using two-dimensional dynamical elasticity mapping. Based on the recently investigated dynamic bulk modulus and effective density imaging technique, an angle-dependent dynamic shear modulus measurement was performed to extract the dynamic Young's modulus distribution of the FDM structures. The elastographic image analysis demonstrated the presence of anisotropic dynamic shear modulus and dynamic Young's modulus existing in the fused deposition modeling 3D printed objects. The non-destructive method also differentiated samples with high contrast property zones from that of low contrast property regions. The angle-dependent elasticity contrast behavior from the ultrasonic method was compared with conventional and static tensile tests characterization. A good correlation between the nondestructive technique and the tensile test measurements was observed.
The focus of this report was to understand the tensile properties and dynamic mechanical properti... more The focus of this report was to understand the tensile properties and dynamic mechanical properties of bamboo powder (BP) reinforced polylactic acid (PLA) composite filaments which were treated with nano calcium carbonate (CaCO 3), cellulose nanofibers (CNF), and micro-crystalline cellulose (MCC) using impregnation modification technology. The storage modulus (E') of nano CaCO 3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments increased compared with BP/PLA composite filaments before the glass transition temperature T g. When the temperature was above T g , the reinforcement effect of nano CaCO 3 , MCC, and CNF gradually became less apparent. The loss modulus (E") and loss factor (tan δ max) of the nano CaCO 3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments was higher than that of BP/PLA composite filaments produced by the "one-step" method. The tensile strength (TS) results showed a similar trend. Compared with the control samples, the TS of nano CaCO 3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments produced by the "one-step" method (and the "two-step" method) increased by 40.33% (and 10.10%), 32.35% (and −8.61%), and 12.32% (and −12.85%), respectively. The TS of nano CaCO 3-BP/PLA, MCC-BP/PLA, and CNF-BP/PLA composite filaments produced by the "one-step" method was slightly higher than those produced by the "two-step" method. The elongation at break (EAB) of BP/PLA composite filaments was higher than that of BP/PLA samples treated with nano CaCO 3 , MCC, or CNF. The PLA and modified BP were readily accessible through a simple mixing process. The rheological investigation of such mixtures showed that nano CaCO 3 , CNF, and MCC have different effects on the processability and rheological properties of composites.
The soy protein isolate (SPI), sodium dodecylbenzenesulfonate (SDBS) and pentaerythritol glycidyl... more The soy protein isolate (SPI), sodium dodecylbenzenesulfonate (SDBS) and pentaerythritol glycidyl ether (PEGE) were used to make biodegradable films in this study. Unlike the usual method that adding sodium hydroxide (NaOH) during the SPI-based film casting, SDBS was used as a surfactant playing the similar role as NaOH. Since NaOH is a chemical with corrosiveness and toxicity, the replacing of NaOH by SDBS might reduce the hazard threat during the utilization of SPI-based films in food packing application. Furthermore, the presentation of SDBS helped dispersing the hydrophobic PEGE into the hydrophilic SPI. PEGE is a crosslinking agent with multiple reactive epoxy groups. The chemical structures and micro morphologies of the fabricated films were investigated by means of FTIR, XRD, and SEM. The thermal stabilities of the films were examined by means of the thermo-gravimetric analysis. After the chemical crosslinking, the ultimate tensile strength of the film was significantly increased, meanwhile, the water absorption was dramatically decreased. It was concluded that the SPI-based film containing 4% PEGE achieved the optimal performance.
The objective of this study was to investigate the deformation behavior of bamboo bundle laminate... more The objective of this study was to investigate the deformation behavior of bamboo bundle laminated veneer lumber (BLVL) manufactured with veneer preprocessing densification technology under low velocity impact loading. The influence of different preprocessing temperatures, times, and stacking sequences was studied with respect to impact loading. Laminates with bamboo bundles parallel to the length direction were labeled as type I, and cross-ply was labeled as type II. The results indicated that delamination and fiber breakage were the main damage models for BLVL made with veneer preprocessing densification technology, and its impact performance under a veneer prepressing temperature of 90°C and a time of 10 min was fairly comparable to that of BLVL without preprocessing densification. The impact index decreased as the densification temperature increased. The impact properties for type II were better than that of type I. The curve characteristic of impact deflection vs. time presented a linear trend, while the curve of impact velocity first decreased and then tended to level off as time elapsed.
The objective of this research was to evaluate the properties of the chemically retted kenaf bast... more The objective of this research was to evaluate the properties of the chemically retted kenaf bast fiber impregnated with the inorganic nanoparticles. High quality kenaf bast fibers were obtained from a chemical retting process. An in situ inorganic nanoparticle impregnation (INI) process was used to introduce the CaCO 3 nanoparticles into the retted kenaf bast fibers. It was found that some of the lignin-based components in the retted fibers were further removed during the INI treatment. From the characterization results, the inorganic nanoparticles CaCO 3 , with different shapes and sizes, appeared at the surface of the impregnated fiber after treatment. Heterogeneous CaCO 3 nanoparticle distribution was observed on the INI treated fibers. The CaCO 3 contents were different at different locations along the impregnated fiber. The presence of CaCO 3 inorganic nanoparticles at the fiber surface increased the root mean square (RMS) surface roughness by 5.8% and decreased the hydrophilic nature of the retted fibers, evidenced by a 59.4% decrease in adhesion force between the fiber and hydrophilic AFM tip. In addition, the impregnation of CaCO 3 dramatically increased the Young's modulus of the fiber by 344%.
Ongoing research into chemically treating southern hardwoods for producing structural composite l... more Ongoing research into chemically treating southern hardwoods for producing structural composite lumber suggests that some improvements may be imparted by modifying the wood. How chemical treatment(s) affect modified wood durability, particularly resistance to Reticulitermes flavipes, was the objective of this study. Water-saturated samples of yellow-poplar, sweetgum, and red oak were heated at 150 C for 30 min in two solutions: water and 1.0% NaOH; controls were also included. Samples were subjected to the AWPA E1-09 no-choice termite test in which mass loss from R. flavipes was determined. The species and treatments independently and significantly affected the mass loss. Yellow-poplar, which had the lowest specific gravity, averaged significantly greater mass loss than sweetgum and red oak for all three exposures. All species treated in water or NaOH showed a higher degree of termite degradation as compared with the controls.
Differing from the hot-pressing method in the manufacturing of traditional wood-rubber composites... more Differing from the hot-pressing method in the manufacturing of traditional wood-rubber composites (WRCs), this study was aimed at fabricating WRCs using rubber processing to improve water resistance and mechanical properties. Three steps were used to make WRCs, namely, fiber-rubber mixing, tabletting, and the vulcanization molding process. Ninety-six WRC panels were made with wood fiber contents of 0%-50% at rotor rotational speeds of 15-45 rpm and filled coefficients of 0.55-0.75. Four regression equations, i.e., the tensile strength (Ts), elongation at break (Eb), hardness (Ha) and rebound resilience (Rr) as functions of fiber contents, rotational speed and filled coefficient, were derived and a nonlinear programming model were developed to obtain the optimum composite properties. Although the Ts, Eb and Rr of the panels were reduced, Ha was considerably increased by 17%-58% because of the wood fiber addition. Scanning electron microscope images indicated that fibers were well embedded in rubber matrix. The 24 h water absorption was only 1%-3%, which was much lower than commercial wood-based composites.
This paper describes the bending creep behavior of two types of bamboo-based products, bamboo-lam... more This paper describes the bending creep behavior of two types of bamboo-based products, bamboo-laminated veneer lumber (BLVL), and glued-laminated bamboo (GLB, also called Bamboo Glulam) at different stress levels for half a year and recovery for the same time. It was found that the stress level of BLVL was more sensitive on creep property than that of GLB; the creep resistance of GLB was worse than that of BLVL in the stress levels of 30-50%; the instantaneous recovery ratio (elastic recovery to elastic creep) decreased with an increase of the stress levels, while the residual ratio (residual deformation corresponded to the total creep deflections) increased with an increase of stress levels for all specimens; Burgers model fit creep data very well for both bamboo-based products, while the recovery Weibull equation does not fit recovery data well for GLB.
The objective of this study was to evaluate the uniformity of density distribution for Bamboo-bun... more The objective of this study was to evaluate the uniformity of density distribution for Bamboo-bundle Laminated Veneer Lumber (BLVL) and its relationship to the stability of mechanical performance. A novel assembly style called one-piece veneer formation technology was developed to enhance the density uniformity, and four different density levels for BLVL were examined by X-ray scanning. The results indicated that the homogeneity of density, the stability of mechanical performance, and the mechanical properties for BLVL could be effectively improved by assembling the bamboo bundles into layers and then combining the layers to make the lumber. The density uniformity in width and thickness directions increased with increasing target density. A negatively linear correlation between density and Coefficient of Variation (COV) of MOR and shearing strength was observed. Partial correlation analysis revealed that when controlling for the variability of density, the linear relationship between density and the COV of MOR became insignificant, and the degree of linear correlation between density and the COV of shearing strength decreased.
Uploads
Papers by Sheldon Shi