Volume 11 Issue 4

In a previous work (Nicu et al. 2013), the flocculation efficiency of three chitosans differing by molecular weight and charge density were evaluated for their potential use as wet end additives in papermaking. According to the promising results obtained, chitosan (single system) and its combination with bentonite (dual system) were evaluated as retention aids, and their efficiency was compared with poly(diallyl dimethyl ammonium chloride) (PDADMAC) and polyethylenimine (PEI). In single systems, chitosan was clearly more efficient in drainage rate than PDADMAC and PEI, especially those with the lowest molecular weights; however, retention is considerably lower. This drawback can be overcome by using dual systems with anionic bentonite microparticles, with the optimum ratio of polymer:bentonite being 1:4 (wt./wt.). In dual systems, the differences in retention were almost negligible, and the difference in drainage rate was even higher, together with better floc reversibility. The most efficient chitosan in single systems was Ch.MMW, while Ch.LMW was the most efficient in dual systems. The flocculation mechanism of chitosan was a combination of patch formation, charge neutralization, and partial bridge formation, and the predominant mechanism depended on the molecular weight and charge density of the chitosan.

Cellulose nanofibrils, as a bionanomaterial with many promising properties, have great potential in composite applications. Herein, well-dispersed and uniform-sized cellulose nanofibrils (CNF) was successfully obtained from commercial bleached softwood kraft pulp, with yields of 79.15% via enzyme-assisted hydrolysis and a subsequent homogenization process. Field emission scanning electron microscope (FE-SEM) confirmed the fiber morphology. Water retention value (WRV) was increased from 107.32% of original pulp to 1383.92% of the resulting CNFs, while crystallinity had no significant changes. Fourier transform infrared (FTIR) spectroscopy indicated the addition of enzyme resulted in the removal of hemicelluloses and lignin. CNFs subjected to enzymatic treatment and homogenization had less entangled network, larger aspect ratio and higher transmittance than those from pure mechanical treatment. They exhibited well-dispersed in aqueous solution and uniform-sized in morphology. These advantages revealed enzyme-assisted process had a remarkable effect on the production of CNFs and made CNFs attractive for nanotechnology and nanomaterial.

This study assessed the effect of selected factors, such as the feed force (Ff = 15, 20, and 25 N), wood species (beech (Fagus sylvatica L.), English oak (Quercus robur L.), and spruce (Picea abies L.)), and the number of saw blade teeth (z = 24, 40, and 60) on cutting power in the cross-cutting of lumber. The cutting was done using a circular saw with a rotating motion of the saw blade at a constant cutting speed (vc) of 62 m.s-1. The tangentially bucked lumber had a relative humidity (wr) of 12% ± 1% and a thickness (e) of 50 mm. For the experiment, four circular saw blades with SK plates, a uniform diameter (D = 250 mm), and identical angular geometry (angle of clearance (α) = 15°, wedge angle (β) = 60°, and rake angle (γ) = 15°) were used. The saw blades had a different number of teeth (z = 24, 40, and 60), and one saw blade had 24 teeth and a chip limiter. The aim of this study was to expand the knowledge about the resulting cutting performance with different combinations of technological process parameters.

The aim of this study was to investigate the flexural properties (bending strength and modulus of elasticity) of Scots pine wood (Pinus sylvestris L.) using micro- and standard-size test specimens. In the standard- and micro-size specimens, the average bending strengths were evaluated as 72.8 and 62.4 MPa, and the bending modulus of elasticity was 9917 and 2884 MPa, respectively. These results showed that the bending strength and modulus of elasticity values of the micro-size specimens were lower than those of the standard-size specimens. The statistically significant effects included the specimen size, individual trees, and the interactions of the specimen size and trees on the bending strength and modulus of elasticity. Furthermore, regression analyses indicated a positive linear regression between the flexural properties of the micro- and standard-size specimens. The results indicated that micro-size specimens can be used to estimate the flexural properties of Scots pine wood when obtaining standard-size specimens is not possible.

The thermogravimetric characterization and gas emission properties during the pyrolysis of rice husk (RH) and rice straw (RS) were compared, and the properties of waste rice husk ash (RHA) and rice straw ash (RSA) from the combustion process were investigated. The results showed that the pyrolysis of RH and RS followed a four-step mechanism. Comparing the emission properties of small molecule bio-syngas in the pyrolysis of these two biomass wastes implied that RS was more suitable for use as feedstock for thermochemical conversion. Chemical and phase analysis results indicated that the RSA was rich in K, Ca, and P and had good potential for use as a soil amendment or as a material for silicate ceramics. The RHA was rich in SiO2 and could be an ideal silica source for silicon compound preparation or a pozzolan source for blended cement concrete production. Morphology analysis on the ash samples revealed that the high content of alkali metals may cause the higher agglomeration tendency of RSA with respect to RHA. The contrast in pore properties of biomass char wastes isolated from the ashes indicated that the char wastes recovered from RHA would be better used as a low-cost precursor in activated carbon production.

This study focuses on changing wood’s bending properties using several types of adhesives. The strength, flexibility, and durability (service life) of laminated wood, glued with four types of adhesives, were examined. The results were compared with solid beech wood, conditioned to 9% moisture content. Depending on the adhesive used, the results indicate that laminated (layered) wood improved the strength and bending characteristics in comparison to the intact wood. Gained knowledge about materials properties have practical applications in the area of dynamic stress (e.g., as components of vibrating machinery mechanisms or in constructing beds, chairs, and sports equipment).

Antifungal potential of bark crude extracts of Pinus strobus L., Pinus douglasiana Martinez, Pinus caribaea Morelet [var. Hondurensis (scheclauze) W. H. G. Barrett & Golfari] and Pinus leiophylla Schltdl. & Cham, for inhibiting mycelial growth to fungus Trametes versicolor (L. ex Fr.) Pilát was investigated. Pinus bark was extracted through a mixture of acetone-hexane-water 54:44:2 V. Bioassays were performed according to the agar dilution method (petri dish) using concentrations of 0.1, 0.5, and 1.0 mg mL-1 for each of the obtained extracts. All extracts showed some inhibition degree. Crude extracts of P. strobus bark showed the greatest inhibition degree. Antifungal potential of all tested extracts at a concentration of 1.0 mg mL-1 was classified as toxic. Through simple regression models, concentrations were calculated in order to achieve a 50% inhibition (IC50) and the minimal inhibition concentration (MIC). MIC values were 1.58, 1.72, 1.24, and 1.94 mg mL-1 for bark extracts of P. strobus, P. douglasiana, P. caribaea, and P. leiophylla, respectively.