Kenaf bast for fiber reinforced polymer composites

Cellulosic fibers sized from the macro-scale to the nano-scale were prepared hierarchically from kenaf bast fibers using chemicals. The process began with a hermetical alkaline retting followed by a bleaching treatment. The bleached fibers were hydrolyzed using inorganic acid, from which microfibers and cellulose nanowhiskers (CNWs) were fabricated. Inorganic nanoparticle impregnation (INI) was used to treat the retted fibers for the improvement of the interfacial compatibility between the fiber and polypropylene (PP) matrix. The retted fibers and INI-treated fibers were used as reinforcement for the PP polymer composites. Film casting process was used to make CNW/PVA composites. The hermetical retting process used in this study produced fibers with high cellulose contents (81-92%) by removing the lignin and hemicelluloses. Higher retting temperature resulted in higher fiber surface hardness and elastic moduli. The tensile strengths and tensile moduli of the fibers decreased as the temperature increased. The SEM images showed the micropores in the cell wall structure for the fibers retted at over 130°C, providing the possibility to anchor nanoparticles into the cell wall. Surface morphology of the INI-treated fibers was examined with SEM, and showed that the CaCO3 nanoparticle crystals grew onto the fiber surface. Energy-dispersive X-ray spectroscopy (EDS) was used to verify the CaCO3 particle deposits on the fiber surface. As the size scale of the fibers decreased, the fiber crystallinity increased from 49.9% (retted fibers) to 83.9% (CNWs). About 23% á-cellulose in the raw kenaf bast fibers had been converted into CNWs. The retted fibers without INI treatment had poor compatibility with the polypropylene matrix. The INI treatment improved the compatibility between the fibers and the PP matrix, resulting in an improvement in kenaf fiber/PP composite tensile moduli and tensile strengths. The CNWs prepared from kenaf bast fiber gave excellent reinforcement for PVA composites. A nine percent increase of CNWs in the CNW/PVA composites yielded significant improvements in tensile strength and modulus of about 46% and 152%, respectively, compared with pure PVA

Evaluation of the Noah\u27s Ark: Wood Mechanical Properties Affected by Water Immersion

This study focuses on the mechanical properties of different wood types related to Noah’s Ark and their degradation over time as the ark experienced over a year in water. The objective of this research was to evaluate the wood mechanical properties affected by water immersion as a function of time to see if the strength and stiffness would be diminished. Wood specimens from white oak, teak, and pitch-coated and non-coated southern yellow pine were chosen, because they represent upper and lower bounds of the elastic moduli and strengths of different wood types found around the world. Teak is thought to best represent gopher (term used in the bible) wood, since it was prevalently used as a structural material in the Middle East. The different wood types were soaked in fresh water and salt water for one year (the total time of the flood event). The tensile, compressive and flexural properties of the wood specimens were tested every two months, and the results were statistically analyzed. Since all of the wood types gave similar degradation trends in their mechanical properties over time, one would expect that the mechanical behaviors of gopher wood would exhibit the same trends. Even pitch was used to coat some wood specimens for comparison to provide understanding of the corrosion protection by water-proofing. The bottom line is that the mechanical properties and consequential dimensional stability of gopher wood would not have changed significantly by water immersion (30% maximum), even if it was in salt water and even if there were no pitch to cover the wood. This 30% reduction is not enough to diminish the structural integrity of the ark

Kenaf Bast Fibers—Part I: Hermetical Alkali Digestion

The objective of this study was to develop a hermetical alkali digestion process to obtain single cellulosic fibers from kenaf bast. Kenaf bast were hermetically digested into single fiber using a 5% sodium hydroxide solution for one hour at four different temperatures (80°C, 110°C, 130°C, and 160°C). The hermetical digestion process used in this study produced fibers with high cellulose content (84.2–92.3%) due to the removal of lignin and hemicelluloses. The surface hardness and elastic modulus of the fibers digested at 130°C and 160°C were improved significantly compared with those digested at 80°C. The tensile modulus and tensile strength of the individual fibers reduced as the digestion temperature increased from 110°C to 160°C. Micropores were generated in fiber cell wall when the fibers were digested at 130°C and 160°C. The studies on the composites that were made from polypropylene reinforced with the digested fibers indicated that the compatibility between the digested fibers and polypropylene matrix was poor

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

KENAF BAST FOR FIBER REINFORCED POLYMER COMPOSITES

Cellulosic fibers sized from the macro-scale to the nano-scale were prepared hierarchically from kenaf bast fibers using chemicals. The process began with a hermetical alkaline retting followed by a bleaching treatment. The bleached fibers were hydrolyzed using inorganic acid, from which microfibers and cellulose nanowhiskers (CNWs) were fabricated. Inorganic nanoparticle impregnation (INI) was used to treat the retted fibers for the improvement of the interfacial compatibility between the fiber and polypropylene (PP) matrix. The retted fibers and INI-treated fibers were used as reinforcement for the PP polymer composites. Film casting process was used to make CNW/PVA composites. The hermetical retting process used in this study produced fibers with high cellulose contents (81-92%) by removing the lignin and hemicelluloses. Higher retting temperature resulted in higher fiber surface hardness and elastic moduli. The tensile strengths and tensile moduli of the fibers decreased as the temperature increased. The SEM images showed the micropores in the cell wall structure for the fibers retted at over 130°C, providing the possibility to anchor nanoparticles into the cell wall. Surface morphology of the INI-treated fibers was examined with SEM, and showed that the CaCO3 nanoparticle crystals grew onto the fiber surface. Energy-dispersive X-ray spectroscopy (EDS) was used to verify the CaCO3 particle deposits on the fiber surface. As the size scale of the fibers decreased, the fiber crystallinity increased from 49.9% (retted fibers) to 83.9% (CNWs). About 23% á-cellulose in the raw kenaf bast fibers had been converted into CNWs. The retted fibers without INI treatment had poor compatibility with the polypropylene matrix. The INI treatment improved the compatibility between the fibers and the PP matrix, resulting in an improvement in kenaf fiber/PP composite tensile moduli and tensile strengths. The CNWs prepared from kenaf bast fiber gave excellent reinforcement for PVA composites. A nine percent increase of CNWs in the CNW/PVA composites yielded significant improvements in tensile strength and modulus of about 46% and 152%, respectively, compared with pure PVA

A CHEMICAL PROCESS FOR PREPARING CELLULOSIC FIBERS HIERARCHICALLY FROM KENAF BAST FIBERS

The objective of this research was to evaluate an all-chemical process to prepare nano-scale to macro-scale cellulosic fibers from kenaf bast fibers, for polymer composite reinforcement. The procedure used in this all-chemical process included alkaline retting to obtain single cellulosic retted fiber, bleaching treatment to obtain delignified bleached fiber, and acidic hydrolysis to obtain both pure-cellulose microfiber and cellulose nanowhisker (CNW). At each step of this chemical process, the resultant fibers were characterized for crystallinity using X-ray diffraction (XRD), for functional groups using the Fourier Transform Infrared spectroscopy (FTIR), and for surface morphology using both the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The chemical components of the different scale fibers were analyzed. Based on the raw kenaf bast fibers, the yields of retted fibers and bleached fibers were 44.6% and 41.4%. The yield of the pure cellulose microfibers was 26.3%. The yield of CNWs was 10.4%, where about 22.6% α-cellulose had been converted into CNWs. The fiber crystallinity increased as the scale of the fiber decreased, from 49.9% (retted single fibers) to 83.9% (CNWs). The CNWs had fiber lengths of 100 nm to 1400 nm, diameters of 7 to 84 nm, and aspect ratios of 10 to 50. The incorporation of 9% (wt%) CNWs in polyvinyl alcohol (PVA) composites increased the tensile strength by 46%

Szczepienie włókien naturalnych cyklodekstryną

Over the years, a multiplicity of grafting modification techniques have been studied to combine the adsorption and wettability of natural fibres with the capacity of cyclodextrins (CDs) to form inclusion complexes. The fixation of CDs on fibres is possible using crosslinking agents or reactive derivatives of cyclodextrins. Various crosslinking chemicals are suitable to bind the hydroxyl groups of non-reactive cyclodextrins with those of natural fibres by way of spraying, padding, surface coating, and impregnation. Nano-composite dense polimer film could also be formed to anchor the cyclodextrin on the natural fibre surface by the methods of hydrogen binding or covalent binding in sol-gel. A vinyl monomer such as glycidyl methacrylate was used to form polymer coatings due to the pendant epoxy group coupled with the –OH of cyclodextrin and natural fibres. This review also focused on the derivatives of CDs with the reactive group reacting with the hydroxyl groups of natural fibres.Przez lata badano wiele technik szczepienia, aby połączyć adsorpcję i zwilżalność włókien naturalnych ze zdolnością cyklodekstryn (CD) do tworzenia kompleksów inkluzyjnych. Utrwalanie CD na włóknach jest możliwe przy użyciu środków sieciujących lub reaktywnych pochodnych cyklodekstryn. Różne chemikalia sieciujące są odpowiednie do wiązania grup hydroksylowych niereaktywnych cyklodekstryn z tymi z włókien naturalnych poprzez natryskiwanie, napawanie, powlekanie powierzchni i impregnację. W celu zakotwiczenia cyklodekstryny na powierzchni włókien naturalnych metodami wiązania wodoru lub wiązania kowalencyjnego w zolu-żelu można zastosować możliwość tworzenia nano-kompozytowej folii polimerowej. W pracy do utworzenia powłok polimerowych użyto monomeru winylu – metakrylan glicydylu. W artykule skupiono się również na pochodnych CD z grupą reaktywną reagującą z grupami hydroksylowymi włókien naturalnych

Kenaf Bast Fibers—Part II: Inorganic Nanoparticle Impregnation for Polymer Composites

The objective of this study was to investigate an inorganic nanoparticle impregnation (INI) technique to improve the compatibility between kenaf bast fibers and polyolefin matrices. The Scanning Electron Microscopy (SEM) was used to examine the surface morphology of the INI-treated fibers showing that the CaCO3 nanoparticle crystals grew onto the fiber surface. Energy-dispersive X-ray spectroscopy (EDS) was used to verify the CaCO3 nanoparticle deposits on the fiber surface. The tension tests of the individual fiber were conducted, and the results showed that the tensile strength of the fibers increased significantly (more than 20%) after the INI treatments. Polymer composites were fabricated using the INI-treated fiber as reinforcement and polypropylene (PP) as the matrix. The results showed that the INI treatments improved the compatibility between kenaf fibers and PP matrix. The tensile modulus and tensile strength of the composites reinforced with INI-treated fibers increased by 25.9% and 10.4%, respectively, compared to those reinforced with untreated kenaf fibers

Aerosol assisted chemical vapour deposition of nanostructured ZnO thin films for NO2 and ethanol monitoring

Gas response control through structural and defect engineering in metal oxides are critical approaches to realize high performance sensors. Herein, we present the fabrication of ZnO thin films containing nanosized structures and high concentration of zinc interstitials for NO2 and ethanol monitoring. The target materials were fabricated by aerosol assisted chemical vapour deposition (AACVD) method on ceramic and glass substrates, and were characterized by complementary analytical techniques. The obtained ZnO nanoparticulate and nanopyramidal thin films yielded an outstanding response of similar to 41 to 1 ppm NO2 and similar to 236 towards 100 ppm ethanol, respectively. The reasons accounting for such an enhancement were revealed by the surface-depletion model in ZnO and the chemisorption energies of oxygen molecules on Zn-i-enriched crystal facets