Volume 13 Issue 1

Antibacterial activity is one of the desired functionalities in paper and board grades, especially for packaging. This study designed a contact-active antibacterial surface using polyvinylamine (PVAm) bonded onto inorganic particles (kaolin), and investigated appropriate ways to utilize the treated inorganic particles as antibacterial carriers to produce antibacterial paper. Antibacterial inorganic particles were prepared by modifying the surface of kaolin through a polyelectrolytes multilayering (PEM) technique with a PVAm and polyacrylic acid system. The pH control during the PEM process affected the adsorption amount of PVAm and dispersion stability of PEM-treated kaolin. The PEM-treated kaolin was applied to prepared handsheets via two ways, internal addition or surface treatment. Only the surface-treated handsheets had a noticeably reduced bacteria ratio. Antibacterial activity was > 99.9% for Escherichia coli and > 99% for Listeria monocytogenes. The inactivation of bacteria with damaging membranes was confirmed by a dual staining method. The surface coverage of the PEM kaolin on the handsheets was an important factor for inactivation of the bacteria. As a result, the surface treatment of antibacterial inorganic particles was determined to be the proper strategy to produce antibacterial paper.

The effects of tenon size were investigated relative to the front to back loading performance of Scots pine (Pinus sylvestris L.) chairs. Forty-five chair frames were constructed with mortise and tenon joints with 9 tenon sizes. Joints were assembled with a 65% solids polyvinyl acetate (PVAc) adhesive. The front to back loading performance of chairs was compared to the acceptable design load levels given in the American Library Association (ALA) specifications. Chair frames were structurally analyzed with the Finite Element Method (FEM) to obtain the moment acting on each joint under loading. The results indicated that a chair became stronger as either tenon width or length increased, but was most affected by its length. As a result of structural analyses, front leg to side rail and back leg to side rail joints carried approximately 73% of the total moment that was induced under the front to back loading. According to the comparison results with acceptable design loads, chairs constructed with 40 mm × 50 mm tenons could meet light service (domestic usage), while the chairs constructed with 50 mm × 50 mm tenons could meet medium service. The chairs constructed with other sizes could not meet any acceptable levels, and thus need reinforcement.

Mimusops elengi seed shell powder (MESSP) was introduced as a new bio-filler in polypropylene (PP). The MESSP was characterized using a particle size analyzer, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and a thermogravimetric analyzer. MESSP was successfully melt mixed with polypropylene to produce bio-composite at various MESSP loading. The processability and properties of the bio-composites were characterized by using processing torques, differential scanning calorimetry, tensile test, water absorption, and SEM. The processability of PP was not affected by the addition of MESSP, which was revealed from the minimum changes in the processing torques, melting temperature, crystallization temperature, and degree of crystallinity. The tensile strength and elastic modulus of the bio-composites were improved with an addition of MESSP of up to 10 wt.%. However, the elongation at break and resistance to water absorption decreased slightly with increased MESSP loading. Morphological observations revealed that the MESSP showed good dispersion and adhesion in the PP matrix of up to 5 wt.% MESSP. Above 5 wt.% MESSP, agglomerates formed, which influenced the physical-mechanical properties of the PP and MESSP bio-composites. Results indicated that PP/MESSP composites can be used to replace PP in applications such as car dashboards and door panel, furniture, and rigid packaging.

The directions of South, North, West, and East had no significant influence on hemp hurd thickness (p > 0.05) based on the data from 100 hemp plants measured and oriented in different directions. As the hemp hurd grew, the thickness of the plants at different orientations also changed. The pectin and ash content in the wide areas were higher than those in the narrow areas. The lignin, holocellulose, alpha cellulose, and hemicellulose content in the wide areas were lower than those in the narrow areas (p = 0.05) in different hemp plants of different genders and plant densities. Additionally, the cell numbers in the wide areas were higher than those in the narrow areas in different locations of hemp plants, of different genders, and varied plant densities (p < 0.05). Thus, the formation of the narrow areas and wide areas in the hemp hurd were caused by the division difference of cambium. The plant hormones were the main influence on the division of cambium. Three particular plant hormones cytokinin (CTK), abscisic acid (ABA), and auxin (IAA) in the wide areas of hemp plants were higher than those in the narrow areas of plants of different genders and plant densities (p < 0.05). The eccentricity had a great influence on the physical and chemical properties of hemp hurd.

The research and refinement of papermaking wastewater treatment and reuse technology are important measures for energy conservation and emission reduction in the papermaking industry. This paper studied the process of biofilm formation and dissolved oxygen mass transfer of biofilms cultivated under different aeration intensities and attempted to enhance the biofilm reactor performance. The removal efficiencies of the chemical oxygen demand, total nitrogen, and ammonia nitrogen through biofilm treatment in two parallel biofilm reactors were higher under the larger aeration intensity (8 L/min) than under the smaller intensity (4 L/min). Macroscopically, this reflected the effect of dissolved oxygen on nitrogen removal. Microscopically, in terms of the dissolved oxygen profiles inside of the biofilms determined using a microelectrode probe, both aerobic and anaerobic layers occurred inside the biofilms, which suggested that simultaneous nitrification and denitrification occurred. The different aeration intensities led to differences in the internal and external dissolved oxygen concentrations in the biofilms, which affected the biofilm growth. This led to different micro-structures, and so the internal metabolism and wastewater treatment performance of the biofilms were not identical.

Parallel strand bamboo (PSB), a processed bamboo composite, has been used as an alternative to wood products in building and engineering applications. Inelastic analysis of PSB members is important because of the evident nonlinearity of the material. The present work conducted experimental investigations on intermediately slender PSB columns subjected to biaxial eccentric loads. The bending failure, which underwent a pronounced nonlinear process, was the major characteristic of the intermediately slender PSB column that had a biaxial compressive load. The mid-height cross section of the columns can be divided into three parts over its depth: the plastic compressive zone, the elastic compressive zone, and the tensile zone. Both the secondary bending and material nonlinearity were important factors that impacted the nonlinear response of the columns. An analytical method was presented for evaluating the load-carrying capacity of intermediately slender PSB columns with rectangular cross sections under biaxial eccentric compression loads. There was good agreement between the results of the experiments and calculations.

Scots pine sapwood samples were pre-treated with a Lewis acid (AlCl₃) and a combination of Lewis and protonic acids (AlCl₃ and H₂SO₄), and were subsequently exposed to respective temperatures of 180 °C and 120 °C for establishing a comparable mass loss with those impregnated with demineralized water and solely thermally modified at 220 °C. Water impregnated samples dried at 120 °C also served as controls. The swelling behavior of all wood samples was examined with respect to maximum swelling in water, anti-swelling efficiency (ASE), shrinkage, and dynamic water vapor sorption at relative humidity ranges of 0% to 95%. The thermal modification at 220 °C diminished swelling and moisture adsorption, and also reduced moisture increment and decrement compared with the unmodified control. However, it was less obvious than both acid pre-treated samples. Excess surface work and Hailwood-Horrobin results calculated from water vapor sorption studies demonstrated that, at comparable mass loss, the available sorption sites were reduced to a greater extent by Lewis acid and combination of Lewis and protonic acids pre-treatment than the sole thermal treatment. This was attributed to more pronounced degradation of polysaccharides, mainly hemicelluloses and amorphous parts of cellulose, and to cross-linking of cell wall polymers due to the acid pre-treatments.

The use of cellulosic materials in the construction of low-rise housing in tropical climates has great potential. Bambusa blumeana (B. blumeana, J.A. and J.H. Schultes), the most abundantly available bamboo species in the Philippines, is a promising alternative material for the construction of cost-efficient buildings. However, to comply with municipal rules and regulations for construction, a comprehensive understanding of the organic raw material is needed to permit its application as a load-bearing structural member. In this study, the physical and mechanical properties of B. blumeana bamboo from a typical growth region of the Philippines were tested according to ISO 22157-1 (2004) and ISO 22157-2 (2004). The characteristic strength values of B. blumeana were as follows: compressive and tensile strengths parallel to the grain of 20 and 95 MPa, respectively; shear strength of 5 MPa, bending strength of 34.6 MPa, and the mean and fifth percentile modulus of elasticity of 13100 and 8600 MPa, respectively. Based on these results, a recommendation for permissible stresses for structural design was made in line with ISO 22156 (2004).

Load limit capacity, stiffness, and failure mechanisms were evaluated for the bending of two new types of furniture joints: one with an adhesive-bonded flat cross fastener, and the other with a frictional eccentric fastener. The results were compared with a commonly known direct thread connection used as a reference. For each of the three investigated types of joints, their strength-displacement curves and failure mechanisms were compared. The obtained results confirmed that the two new fasteners are suitable for making furniture joints with more advantageous load capacity and stiffness, as compared with the thread connection.

A new strategy is described to optimize multiple closely related parameters that are involved in the degradation of lignocellulose. Exo-β-1,4-glucanase, endo-β-1,4-glucanase, and β-glucosidase contained in the broth of Trichoderma viride 3.3711 cultures were used as enzyme solution. Corn stover (CS) pretreated by a combination of H2O2 and lignin peroxidase was used as raw feedstock. A comprehensive hydrolysis index (CHI) of three enzymatic activities was constructed by principal component analysis (PCA). Corn stover (CS) was pretreated with a combination of H2O2 and lignin peroxidase. The accuracy of the CHI was demonstrated by a quadratic regression using the CHI as an independent variable and the yield of the total reducing sugar (Ytrs) as a dependent variable. The results showed that the CHI was closely post-correlated with Ytrs and could be used to optimize the fermentation medium components for T. viride cultures due to a highly significant correlation between CHI and Ytrs. Based on the CHI at 96 h, an optimal medium contained 0.6% fructose, 0.6% xylose, 0.3% bean pulp, 0.15% yeast extract, 0.12% KH2PO4, 0.004% CaCl2, 0.008% FeSO4, 0.006% ZnSO4, 0.012% glycine betaine, and 0.004% polyethylene glycol. The maximum actual Ytrs was very near to the theoretical Ytrs.