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To achieve a sustainable bioeconomy, various bioderived additives have been developed to produce biocomposites, but only a handful of research on biocomposites focuses on the effect of bioderived additives on interpenetrating polymer... more
To achieve a sustainable bioeconomy, various bioderived additives have been developed to produce biocomposites, but only a handful of research on biocomposites focuses on the effect of bioderived additives on interpenetrating polymer networks (IPNs). This study is aimed at understanding the interaction between bioadditives and interpenetrating polymer networks and is the first study to build the relationship between bioadditive ratio and damping factor based on dynamic mechanical analysis. The IPNs were prepolymerized in bulk by isocyanate and poly(oxypropylene) polyol (PPG) with two different molecular weights (PPG 700 and PPG 1000), and then, they were grafted with bisphenol A diglycidyl ether epoxy. The bioadditives were prepared from agricultural waste, sugarcane bagasse, and the effect of the coupling agent 3-glycidoxypropyltrimethoxysilane on a bioadditive surface was also discussed in this study. The results show that modified bioadditives have significant enhancement on tens...
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This study outlines the influence of a series of reaction conditions on the yield and reactivity of the glycidyl etherification reaction of the bark extractive-based bioepoxy monomer (E-epoxy). To maximize the yield and epoxy content, the... more
This study outlines the influence of a series of reaction conditions on the yield and reactivity of the glycidyl etherification reaction of the bark extractive-based bioepoxy monomer (E-epoxy). To maximize the yield and epoxy content, the glycidylation reaction was examined with various substrates, solvents, catalysts, time periods, reaction temperatures, and sodium hydroxide/hydroxyl (NaOH/OHV) ratios. Spray-dried bark extractives were used as substrates due to their higher hydroxyl group content and lower molecular weight compared to the oven-dried bark extractives. A dioxane/water combination was selected from among four solvents based on the yield and epoxy equivalent weights of the final product, and tetrabutylammonium hydroxide was chosen as a ring-opening catalyst due to its effect of suppressing hydrolysis. Furthermore, a response surface methodology was applied to find the optimal reaction time, reaction temperature, and NaOH/OHV ratio of the E-epoxy monomer. The maximum extent of conversion with minimum epoxy equivalent weight was achieved after 4.5 h with an NaOH/OHV ratio of 3.4 at 80 °C. This work identifies the effects of reaction parameters on the yield and reactivity of E-epoxy and sheds new light on the glycidylation reaction between epichlorohydrin and renewable biomass.
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This paper investigates the foaming behaviors of polylactic acid (PLA)/cellulose nanofiber composites and the mechanical properties of the composites and their foams. The composites were fabricated by mixing PLA and nanofibers in a... more
This paper investigates the foaming behaviors of polylactic acid (PLA)/cellulose nanofiber composites and the mechanical properties of the composites and their foams. The composites were fabricated by mixing PLA and nanofibers in a solvent with different fiber contents, followed by drying and hot pressing into test specimens. The composites were then foamed via a batch foaming process with CO2 as a blowing agent at different foaming conditions. The effect of nanofiber content on the cell morphology of PLA was studied. The impact strength and thermo-mechanical properties of PLA composites and their foams were also investigated.
This paper investigates the effect of fiber type and fiber content on the foaming behaviors of cellulose fiber reinforced polylactic acid composites. Two types of cellulosic fibers with different sizes were used: micro- and nano-sized... more
This paper investigates the effect of fiber type and fiber content on the foaming behaviors of cellulose fiber reinforced polylactic acid composites. Two types of cellulosic fibers with different sizes were used: micro- and nano-sized fibers. The composites were prepared by a film casting and hot pressing method and then foamed via a batch foaming process with CO2. The morphology and volume expansion ratio of the samples with different cellulose fiber contents were compared. The results suggested that micro-sized fibers had negative effects on the foam morphology and nano-sized fiber positively influenced the foam morphology. It is speculated that the crystals generated around the fibers affected the cell morphology significantly.
In order to broaden the applications of bio-epoxy resins in high performance sector, an understanding of thermal behavior of these environmentally-friendly biopolymers is essential. This study investigates the thermal degradation... more
In order to broaden the applications of bio-epoxy resins in high performance sector, an understanding of thermal behavior of these environmentally-friendly biopolymers is essential. This study investigates the thermal degradation mechanism of a bio-epoxy resin (E-epoxy) derived from bark extractives in comparison with a petroleum-based epoxy resin. The thermogravimetric analysis (TGA) results show that the activation energy of E-epoxy varied significantly with the extent of degradation indicating a multistage degradation mechanism involving a variety of compounds. According to Fourier transform infrared spectroscopy (FTIR) analysis, the dehydration and crosslinking reactions occurred at low temperatures, while the Claisen chain rearrangement and chain–scission reactions dominated at high temperatures. The pyrolysis-gas chromatography–mass spectrometry (Py-GC/MS) results show that a significant amount of methyl abieta-8,11,13-trien-18-oate, diethyl phthalate, 2,2-isopropylidenebis(3,5-dimethylbenzofuran), and epimanool were detected in the bio-epoxy resins. The newly proposed degradation mechanism of bio-epoxy resins based on structural illustration through FTIR and Py-GC/MS can provide guidance for design of high performance bio-based epoxies.
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Chemical treatments are widely employed to improve the fiber-matrix adhesion in composites based on eco-friendly fibers such as flax. To better understand the influence of these treatments on processing behavior, this study characterized... more
Chemical treatments are widely employed to improve the fiber-matrix adhesion in composites based on eco-friendly fibers such as flax. To better understand the influence of these treatments on processing behavior, this study characterized the surface chemistry and morphology of woven flax fabrics treated by acetone, alkaline, silane and diluted epoxy. Flax/epoxy composites were then manufactured by resin infusion and the flow front and preform thickness evolution was monitored. The alkaline treatment was shown to result in a 50 % increase in equivalent permeability due to an increase in porosity which led to a decrease in flexural properties. The processing results were found to be in good agreement with predictions of a 1-dimensional model. This study suggests that infusion times are not considerably affected by the observed changes in surface energy. However, other implications of the treatments such as an increase in fibrillation can alter the infusion times significantly.
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This work outlines the synthesis and characterization of a green epoxy resin derived from bark extractives. The resins were prepared at various temperatures and catalyst amounts to determine an optimal for the yield and epoxy equivalent... more
This work outlines the synthesis and characterization of a green epoxy resin derived from bark extractives. The resins were prepared at various temperatures and catalyst amounts to determine an optimal for the yield and epoxy equivalent weight value. FTIR and NMR techniques were used to characterize the chemical structures of extractive-based epoxy (E-epoxy) monomers. Measurement results indicated a successful epoxidation of bark extractives after reaction with epichlorohydrin. GPC results revealed that the molecular weights and polydispersities of E-epoxy monomers were lower than that of lignin epoxy (L-Epoxy) monomers. The curing kinetic parameters calculated with the Kissinger method and the Model-Free method showed that EEpoxy
had a lower curing activation energy value than petroleum-based epoxy (P-Epoxy). Compared to P-Epoxy, E-Epoxy displayed comparable tensile strength and thermal stability. Research outcome demonstrated promises of using bark extractives to synthesize epoxy resins replacing toxic bisphenol A.
had a lower curing activation energy value than petroleum-based epoxy (P-Epoxy). Compared to P-Epoxy, E-Epoxy displayed comparable tensile strength and thermal stability. Research outcome demonstrated promises of using bark extractives to synthesize epoxy resins replacing toxic bisphenol A.
Epoxy composites were prepared using diglycidyl ether bisphenol F and water-dilutable diglycidyl ether bisphenol A with curing agents, polyoxypropylenediamine and diethylmethylbenzenediamine, in water or dimethylformamide as a solvent.... more
Epoxy composites were prepared using diglycidyl ether bisphenol F and water-dilutable diglycidyl ether bisphenol A with curing agents, polyoxypropylenediamine and diethylmethylbenzenediamine, in water or dimethylformamide as a solvent. The influence of cellulose nanofibers and solvents on curing kinetics of epoxy composites was investigated. Curing kinetic parameters were calculated using the model-fitting methods and the isoconversional method. Among these, the Sestak–Berggren equation best fit the experimental data. Results indicated that dimethylformamide decreased the reaction rate, whereas water revealed the opposite pattern. Cellulose nanofibers catalyzed the reaction between bisphenol F resins and the aromatic curing agent.
The objective of this study was to investigate the effects of material compositions on the mechanical properties of wood–plastic composites (WPCs) manufactured by injection molding. Using a ratio of wood flour/plastic matrix/MAPP (maleic... more
The objective of this study was to investigate the effects of material compositions on the mechanical properties of wood–plastic composites (WPCs) manufactured by injection molding. Using a ratio of wood flour/plastic matrix/MAPP (maleic anhydride polypropylene)/zinc stearate of 47:47:3:3, the tensile strength and modulus of rupture (MOR) of WPCs manufactured with LDPE (low-density polyethylene) and PP (polypropylene) were found to be larger than those of LDPE and PP themselves. However, contrasting findings were obtained when the polymer matrix was ABS (acrylonitrile-butadiene-styrene). In comparison to the mechanical properties of RPP (recycled polypropylene) itself, the MOR increased and the tensile strength decreased for WPCs manufactured with RPP.The tensile strength, MOR, and storage modulus of WPCs made from PP mixed with 47% wood flours (<180 μm) and 3–4.5% MAPP were larger than those of the other WPCs manufactured in this study. However, the polymer damping peaks showed a contrary result.