Research Interests:
ABSTRACT The goal of this study was to determine the optimum liquefaction time and temperature needed to produce a bio oil such that the thermal and mechanical properties of the bio oil based epoxy thermosets would be optimized.... more
ABSTRACT The goal of this study was to determine the optimum liquefaction time and temperature needed to produce a bio oil such that the thermal and mechanical properties of the bio oil based epoxy thermosets would be optimized. Switchgrass was liquefied at temperatures between 200 and 260 °C for 1–3 h to produce bio oil with varying amounts of functional groups such as hydroxyl groups (OH). The bisphenol A/epichlorohydrin derived liquid epoxy resin was then blended with bio-oil at ratios between 1:1 to 1:4 and cured for mechanical and thermal testing. The optimal recipe for liquefaction was 250 °C for 2 h and the optimal ratio for most properties was a 1:1 (epoxy:oil) ratio. The storage modulus of the bio-modified polymer performed best at this ratio for temperatures greater than 70 °C. Likewise, higher degradation temperatures and lower weight loss upon exposure to acetone solvents also demonstrated the highest crosslinking efficiency at a 1:1 ratio. Vibration spectroscopy confirmed a nearly complete consumption of OH functional groups at this ratio based on the disappearance of the peak absorbance at 3336 cm−1. It was concluded that the severity of liquefaction coupled with precise tuning of epoxy:oil ratio was an effective method to control cross linking while ensuring the highest thermal and mechanical properties of the bio-modified polymer. Furthermore, there was excess diethylene glycol in the bio-oil after liquefaction resulting in a plasticizing effect on the epoxy as indicated by the lower glass transition at lower residence times during liquefaction.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Gelatin and chitosan polysaccharides were chemically modified to get methacrylate functionality to obtain biocompatible hydrogels for use as tissue engineering scaffolds. The methacrylation reaction was verified by 1H‐NMR. The degree of... more
Gelatin and chitosan polysaccharides were chemically modified to get methacrylate functionality to obtain biocompatible hydrogels for use as tissue engineering scaffolds. The methacrylation reaction was verified by 1H‐NMR. The degree of methacrylation was varied from 7% to 40% by changing the molar ratio of polysaccharide to methacrylic anhydride and the type of polysaccharide utilized. After the modification, polysaccharide‐based hydrogels were prepared by free‐radical polymerization in the presence of UV light and Irgacure 184 as a photoinitiator. The physical, chemical, and mechanical performances of the hydrogels were further characterized. Also, the biodegradability and the viability of the polysaccharide hydrogels were investigated using fibroblast cells. These cells were seeded directly onto the hydrogel surface, populated the entirety of the hydrogel, and remained viable for up to 1 week. Altogether, the modified polysaccharides exhibit the properties which make them crucial for applications in the field of regenerative medicine.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Concerning the increased market for bio-based materials and environmentally safe practices, cellulose-based beads are one of the more attractive alternatives. Thus, this work focuses on the generation of functional cellulose-based beads... more
Concerning the increased market for bio-based materials and environmentally safe practices, cellulose-based beads are one of the more attractive alternatives. Thus, this work focuses on the generation of functional cellulose-based beads with a relatively simple and direct method of blending a pre-modified chitosan bearing the targeted functional groups and cellulose, prior to the formation of the beads, as a mean to have functional groups in the formed structure. To this end, chitosan was chemically modified with propargyl bromide in homogenous reaction conditions and then combined with cellulose in sodium hydroxide/urea solution and coagulated in nitric acid to produce spherical shaped beads. The successful chemical modification of chitosan was assessed by elemental analysis, as well as by Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The alkynyl moieties from the chitosan derivative, served as reactive functional groups for click-chemistry as demonstrated by the tagging of the commercial fluorophore Azide-Fluor 488 via CuI-catalysed alkyne-azide cycloaddition reaction, in aqueous media. This work demonstrates the one-step processing of multiple polysaccharides for functional spherical beads as a template for bio-based scaffolds such as enzyme immobilization for stimuli-response applications and bioconjugations.
Research Interests:
Transparent materials with robust mechanical properties are essential for numerous applications and require careful manipulation of polymer chemistry. Here, polyurethane (PU) and acrylic‐based copolymers out of styrene were utilized to... more
Transparent materials with robust mechanical properties are essential for numerous applications and require careful manipulation of polymer chemistry. Here, polyurethane (PU) and acrylic‐based copolymers out of styrene were utilized to synthesize transparent PU–acrylic graft‐interpenetrating polymer networks (graft‐IPNs) for the first time. In these materials, PU imparts greater flexibility, while the acrylic copolymer increases rigidity and glass transition temperature of the graft‐IPNs. Kinetics of the graft‐IPN synthesis was monitored using Fourier transform infrared spectroscopy and 1H NMR spectroscopy through the conversion of the isocyanate group. System compatibility, degree of phase separation and material transparency were evaluated using transmission electron microscopy and UV–visible spectroscopy. Overall, higher compatibility is observed at a higher percentage of styrene in the acrylate copolymer. The thermomechanical properties of the IPNs were quantified using dynamic ...
Research Interests:
Bio-oils obtained from southern yellow pine biomass from two thermochemical conversion processes, fast pyrolysis (FP) and hydrothermal liquefaction (HTL), were investigated. The effects of FP and HTL on the physical and chemical... more
Bio-oils obtained from southern yellow pine biomass from two thermochemical conversion processes, fast pyrolysis (FP) and hydrothermal liquefaction (HTL), were investigated. The effects of FP and HTL on the physical and chemical properties of the bio-oils were characterized. The HTL and FP bio-oil yields were 67 and 36 wt%, respectively. The results indicated that the physical properties of the HTL bio-oil and FP bio-oil were similar; however, there were variations in the composition of the bio-oils from the same biomass. The pH values of the FP and HTL bio-oils were 2.3 and 2.8, respectively. From the GC-MS (gas chromatography–mass spectrometry) analysis, esterified chemical compounds were prevalent in the HTL bio-oil, while phenols and phenolic derivatives were found in both bio-oils. The 31P-NMR (phosphorous nuclear magnetic resonance) analysis of the bio-oils further revealed that both FP and HTL bio-oils are rich in phenolic OH and aliphatic OH functionalities, which could serv...
Research Interests:
Research Interests:
Research Interests:
A theoretical study on reaction energetics to better understand the pyrolysis behavior of lignin-derived from hardwood.
Research Interests:
Abstract Flexible graft-interpenetrating polymer networks (IPNs) were synthesized out of polyurethane (PU) and acrylic-based copolymers using two co-monomers, styrene and methyl methacrylate (MMA). Chemical bonds between the two polymers... more
Abstract Flexible graft-interpenetrating polymer networks (IPNs) were synthesized out of polyurethane (PU) and acrylic-based copolymers using two co-monomers, styrene and methyl methacrylate (MMA). Chemical bonds between the two polymers participating in the interpenetration network were utilized to decrease the system's phase separation. The effect of changing the composition of the two co-monomers on the properties of the IPN system was studied. Dynamic mechanical analysis (DMA), tensile, and shear tests were used to characterize the thermomechanical and mechanical properties of IPNs sheets/plates and IPNs as an adhesive. A scanning electron microscope (SEM) was utilized to characterize the failure mechanism of the tensile dog bone samples. Moreover, impact tests were performed on a sandwich structure with synthesized IPN as an inter-layer adhesive to characterize the toughness and stiffness of the IPN samples. Overall, excellent transparency and impact resistance in visible light range with a wide range of thermo-mechanical properties (from extreme elastomeric to more ductile) was observed in IPN samples, which shows their tremendous potential in various transparent, high-performance applications.
Research Interests:
<jats:p> <jats:fig position="anchor"> <jats:graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" mimetype="image" position="float"... more
<jats:p> <jats:fig position="anchor"> <jats:graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" mimetype="image" position="float" xlink:href="S0883769417000896_figAb" xlink:type="simple" /> </jats:fig> </jats:p>
Research Interests:
Research Interests:
Research Interests:
Single-network hydrogels can have an internal porous structure and biocompatibility, but have lower mechanical properties. Combining these properties with another biocompatible and mechanically strong network can help in mimicking the... more
Single-network hydrogels can have an internal porous structure and biocompatibility, but have lower mechanical properties. Combining these properties with another biocompatible and mechanically strong network can help in mimicking the extracellular matrix of native tissues to make them suitable for tissue scaffolds with desired performance. In the current objective, we combine the properties of poly (ethylene glycol) dimethacrylate (PEGDMA) macromer and polysaccharides as the two components in double networks (DN) for synergistic effects of both components resulting in the interpenetrating polymeric network for making it functional for replacement of injured tissues. The hydrogels were characterized by physical properties like swelling ratio, mechanical properties like tensile and compressive modulus, and rheological behavior. The chemical composition was studied using Fourier transform infrared spectroscopy (FTIR), and the thermal behavior using differential scanning calorimetry (D...
Research Interests:
Polymer composites are becoming an important class of materials for a diversified range of industrial applications due to their unique characteristics and natural and synthetic reinforcements. Traditional methods of polymer composite... more
Polymer composites are becoming an important class of materials for a diversified range of industrial applications due to their unique characteristics and natural and synthetic reinforcements. Traditional methods of polymer composite fabrication require machining, manual labor, and increased costs. Therefore, 3D printing technologies have come to the forefront of scientific, industrial, and public attention for customized manufacturing of composite parts having a high degree of control over design, processing parameters, and time. However, poor interfacial adhesion between 3D printed layers can lead to material failure, and therefore, researchers are trying to improve material functionality and extend material lifetime with the addition of reinforcements and self-healing capability. This review provides insights on different materials used for 3D printing of polymer composites to enhance mechanical properties and improve service life of polymer materials. Moreover, 3D printing of fl...
Research Interests:
The objectives of this study were to utilize bio-oil-based epoxy resin in oriented strand board (OSB) production and investigate the effect of bio-oil substitution in epoxy resin as an adhesive for OSB production. Bio-oil was produced by... more
The objectives of this study were to utilize bio-oil-based epoxy resin in oriented strand board (OSB) production and investigate the effect of bio-oil substitution in epoxy resin as an adhesive for OSB production. Bio-oil was produced by the fast pyrolysis (FP) process using southern yellow pine (Pinus spp.). Bio-oil-based epoxy resin was synthesized by the modification of epoxy resin with FP bio-oil at various substitution levels. Acetone extraction using a Soxhlet process indicated a superior cured reaction of bio-oil and epoxy resin at 20% bio-oil substitution. FTIR spectra corroborated the Soxhlet extraction with the removal of the epoxide peak signature within the cross-linked polymer. Images from the scanning electron microscopy suggested bulk phase homogeneity. OSB panels were tested according to ASTM D1037-12. The modulus of rupture (MOR), modulus of elasticity (MOE), internal bond strength, and water resistance (thickness swell and water absorption) properties of the OSB pa...
Research Interests:
New polysaccharides are being intensely studied as sources of edible materials, with potential application in food packaging systems, eco-materials and the pharmaceutical industry. This investigation aimed to develop biopolymer films... more
New polysaccharides are being intensely studied as sources of edible materials, with potential application in food packaging systems, eco-materials and the pharmaceutical industry. This investigation aimed to develop biopolymer films based on the polysaccharides obtained from chañar (CH) fruit (Geoffrea decorticans). The resulting polysaccharides, from hydrothermal extraction (CHT) and acid extraction (CHA) were hydrodynamically characterized, with density, viscosity, and diffusion coefficient measurements to obtain their properties in an aqueous solution (intrinsic viscosity, shape factor, partial specific volume, hydration value, molecular weight, and hydrodynamic radius). The polysaccharides films (CHTF and CHAF) were characterized with SEM/EDX, DSC, TGA-DTG, FTIR, DRX, mechanical tests, water vapor permeation, colorimetry, antioxidant capacity, and biodegradability, to determine potential applications based on these properties. The results indicated that the extraction method af...
Research Interests:
Research Interests:
The goal of this study was to investigate the role of ethanol and temperature on the hydroxyl and carbonyl groups in biopolyol produced from hydrothermal liquefaction of loblolly pine (Pinus spp.) carried out at 250, 300, 350 and 390°C... more
The goal of this study was to investigate the role of ethanol and temperature on the hydroxyl and carbonyl groups in biopolyol produced from hydrothermal liquefaction of loblolly pine (Pinus spp.) carried out at 250, 300, 350 and 390°C for 30min. Water and water/ethanol mixture (1/1, wt/wt) were used as liquefying solvent in the HTL experiments. HTL in water and water/ethanol is donated as W-HTL and W/E-HTL, respectively. It was found that 300°C and water/ethanol solvent was the optimum liquefaction temperature and solvent, yielding up to 68.1wt.% bio-oil and 2.4wt.% solid residue. (31)P-NMR analysis showed that biopolyol produced by W-HTL was rich in phenolic OH while W/E-HTL produced more aliphatic OH rich biopolyols. Moreover, biopolyols with higher hydroxyl concentration were produced by W/E-HTL. Carbonyl groups were analyzed by (19)F-NMR, which showed that ethanol reduced the concentration of carbonyl groups.
Research Interests: Chemistry, Water, Polymers, Medicine, Multidisciplinary, and 13 moreBiomass to fuel conversion, Biopolymers, Ethanol, Based Polyol, Solutions, Thermochemical conversion of biomass, Pinus Taeda, Bio Oil, Phosphorus NMR, Production of Polyols from Non Petroleum Sources, Solvents, Bioresource technology, and Hydroxyl Radical
Research Interests:
Research Interests:
Research Interests:
Research Interests:
There is substantial demand in medical and industrial sectors for coatings, films and fibers that prevent bacterial adhesion and growth. Pathogenic bacteria form biofilms that affect human health, producing considerable economic loss and... more
There is substantial demand in medical and industrial sectors for coatings, films and fibers that prevent bacterial adhesion and growth. Pathogenic bacteria form biofilms that affect human health, producing considerable economic loss and human morbidity/mortality. These films are especially troublesome in the health care field (hospital-acquired infections and infections from indwelling medical devices), the military (infections from protective apparel), drinking water supplies (obstruction of pipes and contamination of water distribution systems), and food industries.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Fast pyrolysis of pine wood was carried out to yield a liquid bio-oil mixture that was separated into organic and aqueous phases. The organic phase (ORG-bio-oil) was characterized by gas chromatography–mass spectroscopy, 31P-nuclear... more
Fast pyrolysis of pine wood was carried out to yield a liquid bio-oil mixture that was separated into organic and aqueous phases. The organic phase (ORG-bio-oil) was characterized by gas chromatography–mass spectroscopy, 31P-nuclear magnetic resonance spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. It was further used as a raw material for producing a mixture of biphenolic compounds (ORG-biphenol). ORG-bio-oil, ORG-biphenol, and bisphenol-A were reacted with cyanogen bromide to yield cyanate ester monomers. Cyanate esters were characterized using FTIR spectroscopy and were thermally cross-linked to develop thermoset materials. Thermomechanical properties of cross-linked cyanate esters were assessed using dynamic mechanical analysis and compared with those of cross-linked bisphenol-A-based cyanate ester. ORG-biphenol cyanate ester was observed to have a superior glass transition temperature (350–380°C) as compared to bisphenol-A cyanate ester (190–220°C). Cyanate es...
Research Interests:
Research Interests:
Chionanthus retusus and most Osmanthus spp. possess torus-bearing intervascular pit membranes in their woods. Because the genera involved are thought to be closely related and are members of the subtribe Oleinae, we hypothesized that... more
Chionanthus retusus and most Osmanthus spp. possess torus-bearing intervascular pit membranes in their woods. Because the genera involved are thought to be closely related and are members of the subtribe Oleinae, we hypothesized that torus morphology should be similar across taxa. A study combining light, scanning electron, and atomic force microscopy indicates that tori in both genera comprise a bipartite thickening containing a central pustular region and an encircling corona. Removal of incrusting material from the torus exposes subtending sets of parallel microfibrils. We hypothesize that the torus structures of C. retusus and Osmanthus spp. (as represented by O. armatus) have the same morphology. Optimizing torus-bearing pits on published molecular phylogenies of the subtribe Oleinae indicates parallel evolution as an explanation for torus similarity between these two groups, although a robust and well-resolved phylogeny of the Oleaceae is still lacking. A brief study of the wo...
Research Interests:
A novel self-curing epoxy resin was synthesized using bio-oil. Bio-oil was produced by hydrothermal liquefaction of loblolly pine and utilized as a biopolyol in the synthesis of bio-oil-based epoxy resin (BOBER) for the first time.... more
A novel self-curing epoxy resin was synthesized using bio-oil. Bio-oil was produced by hydrothermal liquefaction of loblolly pine and utilized as a biopolyol in the synthesis of bio-oil-based epoxy resin (BOBER) for the first time. Hydroxyl groups in bio-oil were analyzed by quantitative 31 P NMR. It was found that not only does the total hydroxyl number of bio-oil influence the yield and epoxy equivalent weight of BOBER, but also the distribution of hydroxyl groups within bio-oil (aliphatic, phenolic, and acidic OH) played an important role in the determination of the optimum amount of catalyst in the synthesis of BOBER. Differential scanning calorimetry analysis proved the self-curing phenomena of BOBER, and Fourier transform infrared spectroscopy suggested that etherification reaction was the dominate reaction during the self-curing. Glass transition temperature, cross-linking density, and the storage modulus of self-cured BOBER were calculated using a dynamic mechanical analyzer.
Research Interests:
Research Interests:
Hybrid composite phenolic foams are reinforced with chopped glass and aramid fibers in varied proportions. The mechanical properties are measured and compared with those of foams reinforced with only aramid and glass fibers. The... more
Hybrid composite phenolic foams are reinforced with chopped glass and aramid fibers in varied proportions. The mechanical properties are measured and compared with those of foams reinforced with only aramid and glass fibers. The compression and shear properties of the hybrid reinforced foams are also compared with those of commercial polyurethane foams. The reinforced hybrid phenolic foams exhibit greater resistance
Research Interests:
Research Interests:
Large amplitude oscillatory shear (LAOS) is frequently capable of generating macroscopic alignment from an initially random orientation distribution in ordered polymer fluids. Side-group liquid crystalline polymers are of special interest... more
Large amplitude oscillatory shear (LAOS) is frequently capable of generating macroscopic alignment from an initially random orientation distribution in ordered polymer fluids. Side-group liquid crystalline polymers are of special interest in that the flow field may couple ...