Volume 6 Issue 3

The aim of the research was to study the potential of lignocellulosic fillers such as flour of rice hull, wood saw dust, sanding flour from Medium Density Fiberboard (MDF), and sawdust from particleboard as reinforcement for recycled high density polyethylene. Natural filler HDPE composites were made from recycled HDPE and lignocellulosic fillers at 60% by weight filler loadings using a dry blend/hot press method. In all compounds 3 per hundred compound (phc) Maleic Anhydride Polyethylene (MAPE) was used. Nominal density and dimensions of the panels were 1g/cm3 and 35×35×1 cm. Physical properties of panels including short and long-term of water absorption and thickness swelling and mechanical properties, including flexural modulus, flexural strength, strain at yield, and energy to yield point were studied. Composites containing sanding flour from MDF showed higher short-term values of water absorption and thickness swelling. For the long term, such as maximum values of water absorption and thickness swelling and diffusion coefficient, composites including wood sawdust showed higher values, and composites contain rice hulls exhibited the lowest values. In addition, composites made from sanding flour from MDF showed high value of the swelling rate parameter. Water absorption behavior of studied composites followed Fick’s model. The flexural properties of composites were investigated with reference to the effect of filler type. Composites containing sanding flour from MDF and particleboard sawdust exhibited better flexural properties than others and composites containing wood sawdust showed the lowest values.

The structure of wood is so compact that enzymes are too large to penetrate into the structure and thereby attack the wood components for modifications that can be valuable for various purposes. Here we present a pretreatment method based on traditional kraft pulping, which opens the wood structure, so that enzymes are able to attack the wood components. To study this kind of chemical pretreatment, spruce wood samples were treated at similar conditions used in kraft cooking at varying intensities (H-factors). To verify if the structure was “opened” for enzymes, the pretreated wood samples were incubated with a cellulolytic culture filtrate, and the released reducing sugar concentration after the enzymatic hydrolysis was measured. The results indicated that un-pretreated wood fibers could not be attacked by the enzymes, but already relatively mild pretreatment was sufficient for letting the culture filtrate attack wood polysaccharides, and more intensive treatments opened the structure further. The mildest treatments did not cause any significant yield losses of lignin (Klason lignin). Some galactogluco-mannans were however lost during the pretreatments. The mechanisms behind the effect and the technical significance of the method are discussed.

Whiskers, having large length/diameter ratio, are fiber-shaped single crystals. The technical possibility of using calcium carbonate whiskers as papermaking filler to replace conventional powder-like calcium carbonate was investigated. The results showed that it may be feasible to use calcium carbonate whisker as papermaking filler. Compared with conventional precipitated calcium carbonate, calcium carbonate whisker had higher retention efficiency. The use of calcium carbonate whisker also favorably affected the strength properties of paper sheets. A model was proposed to suggest the mechanism for paper strength improvement. The whiskers filled in paper sheets could increase the friction between fibers, thus increasing bonding strength. Moreover, the strength properties of paper were further improved because calcium carbonate whiskers were partly embedded in pulp fiber walls.

Sugarcane bagasse (SCB) is an important by-product from the sucro-alcohol industry in Brazil, and it is a convenient raw material for new applications. In this study, SCB was modified with thiophosphoryl chloride in order to attach the P=S chelating moiety to the fibers, aiming at the production of a new material (SCB-F) with increased cadmium adsorption capacity. The SCB-F was characterized by elemental analysis, infrared spectrometry, thermogravimetry coupled to mass spectrometry, and acid-base titration. Adsorption isotherms for Cd(II) revealed a maximum adsorption capacity (qmax) of 74 mg/g, over 60 times higher than that of unmodified SCB. SCB-F thus represents a potentially interesting product for the decontamination of water bodies or effluents polluted with heavy metals.

Maleopimaric acid (MPA) can be used for polymer materials as a rosin derivative. In this study, rosin-based waterborne polyurethane (RWPU) was prepared with different content of maleopimaric acid polyester polyol (MAPP), which was synthesized from MPA. The properties of RWPU were studied by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Other properties including tensile strength, elongation at break, and water absorption were also determined. The onset decomposition temperature of RWPU with 30 wt% MAPP is improved from 170°C to 237°C, compared to the pure WPU. The tensile strength of the derivative was increased from 7.24 MPa to 23.24 MPa as well relative to the default polyurethane. The water absorption decreased significantly from 78.6% to 14.7%.

Cellulose fibers were isolated from sugarcane bagasse in three stages. Initially sugarcane bagasse was subjected to a pre-treatment process with hydrolyzed acid to eliminate hemicellulose. Whole cellulosic fibers thus obtained were then subjected to a two-stage delignification process and finally to a bleaching process. The chemical structure of the resulting cellulose fibers was studied by Fourier Transform Infrared (FTIR) spectroscopy. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) were used to analyze the effects of hydrolysis, delignification, and bleaching on the structure of the fibers. Two different thermal analysis techniques were used to study the bleaching cellulose fibers. These techniques confirmed that cellulose fibers were isolated from sugarcane bagasse. A future goal is to use these fibers as reinforcement elements in composites, organic-inorganic hybrid, and membranes for nanofiltration.

Based on global research and experiences producing newsprint from bagasse, the possibility of using bagasse chemical pulp in the furnish of local mill-made mixed hardwood CMP pulp was studied at laboratory scale, for making newsprint. Bagasse soda chemical pulp at digester yield of about 47% was bleached to about 60% brightness by single stage hydrogen peroxide. The effects of using up to 30% bagasse chemical pulp in a blend with hardwood CMP pulp, with or without softwood kraft pulp, were studied. The results showed that superior hand sheet properties could be achieved by using bagasse chemical pulp; in comparison with main mill pulp furnish (83% hardwood CMP pulp and 17% imported long fiber pulp). In other words, by using bagasse chemical pulp in a blend with local mill made hardwood CMP pulp, acceptable newsprint could be made with considerable reduction in the consumptions of hardwood species and softwood reinforcing kraft pulp.

Epoxidization is an interesting way to develop a new application of lignin and therefore to improve its application potential. In this work, kraft lignin-based epoxy resins were obtained by the epoxidization reaction, using the kraft lignin recovered directly from pulping liquor and modified by a methylolation reaction. The methylolated lignins were obtained by the reaction of original kraft lignin with formaldehyde and glyoxal, which is a less volatile and less toxic aldehyde. 1H-NMR spectroscopy showed that methylolated kraft lignin has more hydroxymethyl groups than glyoxalated kraft lignin. For the epoxidization reaction we studied the influence of the lignin:NaOH (w/w) ratio, temperature, and time of the reaction on the properties of the prepared epoxidized lignins. The structures of lignin-based epoxy resins were followed by epoxy index test and FTIR spectroscopy. Optimal conditions were obtained for lignin-based epoxy resin produced at lignin/NaOH = 1/3 at 70 ºC for 3h. Thermogravimetry analysis (TGA) revealed that the epoxidization enhances the thermal stability of lignins and may allow a wider temperature range for applications with lignin epoxy-PF blends.

The objective of this study was to investigate the effect of natural weathering in ground contact on biological resistance, modulus of rupture, and color stability of heat-treated alder wood. Chemical composition of weathered wood was also studied by FTIR-ATR spectra. Wood stakes were heated at 150, 180, and 200°C for periods of 2, 6, and 10 hours, and the stakes were subsequently exposed to natural weathering and decay in a field area located in the north of Turkey for 3 years. The decay index of heat-treated stakes was lower than that of the controls. The weight loss prevention ratio had an increasing tendency with increasing treatment temperature and length of time. Depending on the treatment parameters, heat treatment reduced the modulus of rupture by up to 50%; however decay caused by soil micro-organisms gave rise to a greater loss of modulus of rupture than heat. Weathering processes caused remarkable color changes in the samples. FTIR-ATR spectra showed significant deformations and degradations in wood components, especially in the hemicelluloses of heat-treated samples. Degradation of hemicelluloses increased with an increase in heat temperature and exposure time.

Adsorption and recovery of hexavalent uranium from dilute aqueous solutions by low cost citrus waste biomass was investigated by performing adsorption-desorption studies. Different samples of citrus waste biomasses were screened for removal of U(VI) from aqueous solutions. The results indicated that the biosorption capacity was strongly affected by the solution pH, biosorbent dose, contact time, and initial uranium concentration. Uranium binding by the test biomass was rapid, achieving >79% sorption efficiency within 15 min, and the equilibrium was established in 60 min. Optimum biosorption capacity (qe) was observed at pH 4.0, biosorbent dose 0.1 % (w/v), initial uranium concentration of 100 mg/L. The kinetic data fitted well to a pseudo-second-order rate equation (R2=0.980). The adsorption process conformed to a Langmuir adsorption isotherm model. Gibbs free energy (ΔGo) and enthalpy change (ΔHo) indicated that reaction was spontaneous and exothermic in nature at the studied temperatures. FT-IR studies showed the involvement of carbonyl, carboxyl, and amide groups in the biosorption process. Treatment of biomass with different reagents affected its biosorption capacity, and maximum removal (70.63%) was recorded with polyethyleneimine (PEI) treated biomass. EDTA had the best effects as an eluent, showing 94.7% desorption capacity.