Volume 6 Issue 4

The drying process of Norway spruce (Picea abies [L.] Karst) wood exposed to infrared heat radiation was studied by measuring the moisture profiles of the wood samples at controlled temperature during drying. The thermal treatment was executed in a purpose-made industrial pilot-plant containing the heat radiators covered by infrared (IR) transmition filters. The moisture content of the samples was detected at certain stages of the process. Based on the results of exposing the samples to IR radiation for 15, 25, 35, and 45 hours, the drying mechanism of wood is discussed. The moisture transport mechanism was explained by a semipermeable membrane process considering the moisture content as a dilute aqueous solution. If the semipermeable cell wall allows only the passage of water but not that of solute molecules, water diffusing from the region of higher (center) to lower (periphery) water content produces osmotic pressure difference between the two sides of the cell walls. The importance of this osmosis was considered in the approach of moisture migration.

In this study the effect of virgin and recycled plastics on water absorption of nanocomposites from newsprint fiber and organoclay was studied. Newsprint fiber was mixed with either virgin or recycled polypropylene (PP) at 30% by weight fiber loading. The samples were made by melt compounding and then injection molding. The concentration was varied as 0, 2.5, and 5% for nanoclay. The amount of coupling agent was fixed at 10% for all formulations. The long-term water absorptions of samples were evaluated by immersing them in water at room temperature for several weeks, and water diffusion coefficients were also calculated by evaluating the water absorption isotherms. The results indicated that whether or not virgin plastic is used has a significant effect on the water absorption of composites. The water absorption of the newsprint fiber/recycled plastic composites was higher than those of virgin plastics. Furthermore, with addition of nanoclay content in composites, water absorption decreased. Water absorption of all formulations was proved to follow the kinetics of a Fickian diffusion process. Morphological findings showed the formation of intercalated morphology and better dispersion with 2.5% of nanoclay.

The objective of this work was to compare the adsorption of different polysaccharides and cellulose derivatives on cellulose nanofibril films. Cellulose films having the native cellulose I structure were prepared from hardwood kraft pulp by extensive mechanical disintegration. Further fractionation enabled the preparation of reproducible, nanometer-scale thickness films. Systematic comparison by Quartz Crystal Microbalance with Dissipation (QCM-D) showed that various industrially available galactomannans have almost as good affinity to cellulose surface as xyloglucan and that most of the polysaccharides attach irreversibly to cellulose nanofibrils at low pH (4.5) and intermediate ionic strength (10 mM). SPR results support the QCM-D findings. Atomic Force Microscopy (AFM) imaging and Digital Pulsed Force Mode (DPFM) measurements further confirmed that a uniform non-aggregated layer of polysaccharides was formed that changed the properties of the NFC film.

100% natural tannin-based rigid foams were synthesized. Tannin-furfuryl alcohol networks were polymerized in an acid environment applying a temperature between 120° and 160°C. The process was developed in two ways: in a ventilated oven and in between the heated plates of a press. The foams produced showed a high homogeneity in both cases. By modifying the formulation in terms of type and amount of components it was possible to produce two kinds of foams: (1) light with density of approximately 50 Kg/m³, and (2) resistant having a density of approximately 180 Kg/m³. The compression resistance and the water absorption of these materials were evaluated. The results of these tests, in comparison with those of formaldehyde-reinforced tannin foams, indicated that these lightweight foams have lower mechanical strength but higher water affinity. The latter was also demonstrated with moisture uptake measurements. Particular attention was dedicated to the press-produced foams for their possible application as core-layer for lightweight composite panels.

Kinetic modeling of enzymolysis of pulp fiber waste pretreated by a wet oxidation process was studied. First, a wet oxidation pretreatment of fiber waste was carried out. It was found that hemicellulose were removed efficiently, yielding material with a pentosan content of 4% (based on the o.d. biomass). A statistical kinetic model was developed based on the experimental results of the enzymatic hydrolysis of wet oxidation pretreated material. The model can be described as follows: RSY (reducing sugar yield)=12.48×C0.4261×(1-e-0.2021t) ×100%, an equation that can be used to predict the reducing sugar yield in an enzymolysis process. The RSY by enzymatic loading of 35FPU/g achieved almost the highest yield after 48 h, and there was no significant improvement with further extension of the enzymolysis time. The modeling was validated within the enzymatic loading range of 15 to 35FPU/g and provided a satisfactory interpretation of the experimental data.

Effects of alkali treatment of rice straw flour on the mechanical properties of rice straw flour-polypropylene composites were investigated. Rice straw flour (40 mesh) was first treated with sodium hydroxide using two concentrations of sodium hydroxide, 5 and 10% (W/W), and two treatment times (45 and 90 min) for a total of four treatments. The composites were then made with the rice straw flour as a filler (30%), polypropylene (65%) as a matrix, and maleic anhydride (5%) as a coupling agent. The polypropylene/rice straw flour mixtures were blended in an internal Haake mixer and made into molds that were later used for mechanical testing. The results showed that the treatment of rice straw flour with 5% alkali (W/W) increased the tensile modulus and impact strength. Longer treatment time also resulted in a higher tensile modulus and impact strength. The fiber/matrix interaction was analyzed from the mechanical data and morphological (SEM) studies. Treatment of rice straw flour with 10% alkali (W/W), however, decreased these properties even under a longer treatment time. Increasing the alkali concentration and treatment time increased the flexural modulus, flexural strength, and tensile strength of the composites. The SEM results showed greater adhesion between the rice straw flour and the polypropylene matrix at higher alkali concentrations and longer treatment times.

The effects of different circular saws on surface roughness were determined for heat-treated wood, including Scots pine (Pinus sylvestris L.), eastern beech (Fagus orientalis L.), Uludağ fir (Abies bornmülleriana Mattf.), and sessile oak (Quercus petraea L.), which are used commonly in Turkey. Samples were heat-treated for 3, 5, or 7 hours at 140 or 160ºC, and cut with circular saws with 28, 48, 60, 72, or 96 teeth. Then, the surface roughness of the samples was determined using a scanning device (TIME TR200) with respect to the ISO 4287 standard. Heat treatment increased the surface roughness of the wood used, and changed the colour of the wood. To obtain smooth surfaces with or without heat treatment, a circular saw with 28 teeth and a double chamfered (WZ) mouth profile is recommended.

Surface treatment is an important step of papermaking, namely for improving the final product quality. For uncoated printing and writing papers (P&W), surface sizing is becoming a common practice for controlling paper surface characteristics and liquid spreading and absorption. This work aims at evaluating the potential of assessing and controlling paper surface chemistry, by analyzing the impact of the application of different surface sizing formulations both on the chemical surface characteristics of the modified paper samples and on the final printing quality. For that, blends of cationic starch and minor quantities (5%, 10%, and 20% w/w) of four distinct copolymers of styrene were used, resulting in a total of 12 different surface sizing formulations. A sample surface sized only with cationic starch was taken as reference. Surface chemical properties were determined by using contact angle measurements and inverse gas chromatography. Finally, the inkjet printing quality was evaluated. The results revealed that the surface sizing treatments tested have a substantial influence on the surface energetics and partially explain the differences detected in the inkjet printing quality.

Scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy were used for determination of morphology, crystal structure, and surface chemical groups. Thermal behavior was analyzed by thermogravimetric analysis. can induce cellulose folding, surface erosion, and , together with the shorter average length of NCC (96 nm) than that prepared without ultrasonication (150 nm). Due to the smaller size and larger number of free ends of chains, the thermal stability of NCC was lower than BSKP. The degradation of BSKP exhibited one significant pyrolysis stage within the range of 300 to 420 °C. In contrast, UH-NCC exhibited three pyrolysis stages within the range of 210 to 450 °C. NCC prepared with ultrasonication decomposed at lower temperature and over a wider temperature range, together with higher char yield of 43% (compared with 27% for that without ultrasonication). The obtained NCC had similar (74%).

Empty fruit bunches (EFB) from palm oil were characterized. The holocellulose (66.97%), α-cellulose (47.91%), and lignin (24.45%) are similar to wood materials, and various non-wood materials, but the fiber length is shorter (0.53 mm). The influence of operational variables in the EFB pulping [formic acid (75-95%), hydrochloric acid (0.05-0.15%), and time (30-150 min)], on the yield, kappa number, viscosity, and brightness of the pulps was studied. By using a factorial design, equations that reproduced the experimental results for the dependent variables, errors less than 10% were obtained. These equations could be used to find suitable conditions, so that operating with not too high values of operating variables (with minor costs of capital and of operation), pulps could be obtained with acceptable properties. In this way, a cellulosic pulp with a 42.3% yield, 22.7% brightness, and a 512 mL/g viscosity was obtained under the following conditions: 92.5% of formic acid, 0.075% of hydrochloric acid, and a time of 60 min. A pulp (31.1 kappa number and 606 mL/g viscosity) was bleached by EPabOPoP sequence, achieving a brightness of 69.4%, a loss of viscosity and yield of 34.8% and 13.1%, respectively. The residual liquor from the pulping with formic acid 95%, 0.05% hydrochloric acid and 30 min, provides a liquor with 18.2% residual lignin, 4.1% glucose, 9.8% xylose, and 1.2% arabinose, all on dry weight of original material.