Research Articles

Although several authors have studied 3D forming using the press forming process, the gas tightness of polymer-coated paperboard trays has not been widely researched. In this paper, the effect of blank holding force on the surface quality and tightness of press-formed paperboard trays was researched. The press-formed trays were heat-sealed with a multilayer polymer lid. The tightness of the trays was analyzed by following the oxygen content of the packages over the course of 14 d and by using a penetrant coloring solution to locate possible leaks. The results indicate that the blank holding force had a great effect on the quality and tightness of the trays, especially in the case of a rectangular geometry. The geometry of the formed trays played a significant role in process parameter selection, and more demanding geometries emphasize the importance of parameter optimization. However, with the correctly selected parameters, the use of modified atmospheric packaging (MAP) in polymer coated paperboard trays was shown to be possible. The oxygen content of both analyzed geometries was found to be less than 1% 14 d after sealing. It was also demonstrated that the gas tightness of a seal cannot be confirmed using a penetrant solution test exclusively.

The liquid hot water (LHW) pretreatment on cotton linter (CL) was carried out using an autoclave heated in a hot oil bath. The LHW pretreated CL (LCL) was dissolved in NaOH/urea and LiOH/urea aqueous solutions and subsequently used to produce cellulose membrane. The effects of LHW pretreatment, amount of cellulose, and type of alkaline solvent on properties of cellulose solution and cellulose membrane were studied. The formation of cellulose II and crystallinity index (CrI) on the cellulose membranes were confirmed by X-ray diffraction (XRD). The morphology of cellulose membranes were observed by field emission scanning electron microscopy (FESEM). The LHW pretreatment resulted in higher cellulose solubility, higher cellulose solution viscosity, and improved properties of regenerated cellulose products compared to non-treated cellulose. Results also revealed that the amount of cellulose used affected the solubility and viscosity of the cellulose solution and the higher dissolving power of the LiOH/urea system as compared to the NaOH/urea system. In fact, higher solubility and viscosity properties are key factors in many cellulose applications such as membranes, fibers, hydrogels, and other regenerated cellulose products.

Both non-destructive and semi-destructive tests can potentially be very efficient methods for the assessment of structural timber density. This paper describes an investigation into the suitability of three techniques: core drilling, probing, and screw withdrawal. It presents the results after testing 150 pieces of large cross-section (80 mm x 120 mm) structural timber of radiata pine (Pinus radiata D. Don.) from a Spanish source. A strong correlation was found between specimen density and core drilling. Meanwhile, there was also a meaningful correlation with the screw withdrawal, and an acceptable correlation with probing. Even though differences were observed in their predictive capacity, none of these procedures should be rejected as a way of estimating density, as each has its own respective advantages and limitations.

Various soybean straw (stem and pod) samples were dissolved in 8% lithium chloride/dimethyl sulfoxide (LiCl/DMSO) following 4 h of planetary ball-milling. The solubility, extractable lignin yield, and crystal structure of the ball-milled soybean straw were greatly affected by the ball-milling pretreatment. The dissolved soybean straw could be regenerated by being poured into excess distilled water under rapid stirring. The total regenerated fraction yield decreased with the increase in the duration of ball-milling. Approximately 10% to 25% of the straw mass was lost in the dissolution-regeneration procedure. For comparison, ethylenediamine (EDA)-pretreated soybean straw was also completely dissolved in 8% LiCl/DMSO to form a homogeneous solution containing 1% straw after 24 h of continuous stirring. The dissolution-regeneration performance of soybean straw submitted to the EDA pretreatment was quite different due to the lack of vigorous ball-milling.

Hemp (Cannabis sativa L.) shiv has great potential for the production of bio-composites as a reinforcement material. To gain more information about hemp shiv, this research studied the influence of gender on the physical and mechanical properties of the fiber cell wall in the shiv of three dioecious hemp plant varieties by optical microscopy, image analysis software, WXRD, and nanoindentation. The results show that a hemp plant’s gender greatly influences the properties of hemp shiv. While long and thin in female hemp shiv, the fibers are shorter with a larger diameter in male hemp shiv. In addition, the cell walls in female shiv are thinner than those in male shiv. The microfibril angle (MFA), relative degree of crystallinity, elastic modulus, and hardness values of fiber cell walls as well as the lignin content in male hemp plants are higher than those in female hemp plants. Besides, the relationship between mechanical properties and MFA do not align with those observed in previous research, which shows that the gender of an individual plant has a greater effect on the mechanical properties of the fiber cell wall than does its MFA. Thus, when the fiber from this dioecious plant is investigated or used, the sex of the plant should be known and considered.

A TCF bleaching sequence consisting of a urea pretreatment stage (U), laccase-mediator system stage (L), alkaline extraction stage (E), and hydrogen peroxide bleaching stage (P) was used to study the effect of five independent variables on the dependent variables pulp properties, hydrogen peroxide consumption, and residual enzyme activity. Results showed that the most influential variable was L stage pulp consistency, followed by mediator and laccase dosages. On the other hand, oxygen pressure did not have a significant effect. The optimal UL partial sequence significantly enhanced the EP bleaching sequence: 49.8% vs. 33.4% delignification, up to 65.6% ISO vs. 56.3% ISO bleached brightness, and 50.3% vs. 89.9% peroxide consumption in the P stage. The ULE partial sequence also improved an ECF bleaching sequence (ULED0E1D1): 0.6 vs. 1.0 final kappa number; 82.7% ISO vs. 76.0% ISO brightness; and 54.1 N∙m∙g-1 vs. 51.9 N∙m∙g-1 and 3.3 KPa∙m2∙g-1 vs. 2.7 KPa∙m2∙g-1, tensile and burst indexes, respectively, when compared to the control D0E1D1 sequence.

Various soybean straw (stem and pod) samples were dissolved in 8% lithium chloride/dimethyl sulfoxide (LiCl/DMSO) following 4 h of planetary ball-milling. The solubility, extractable lignin yield, and crystal structure of the ball-milled soybean straw were greatly affected by the ball-milling pretreatment. The dissolved soybean straw could be regenerated by being poured into excess distilled water under rapid stirring. The total regenerated fraction yield decreased with the increase in the duration of ball-milling. Approximately 10% to 25% of the straw mass was lost in the dissolution-regeneration procedure. For comparison, ethylenediamine (EDA)-pretreated soybean straw was also completely dissolved in 8% LiCl/DMSO to form a homogeneous solution containing 1% straw after 24 h of continuous stirring. The dissolution-regeneration performance of soybean straw submitted to the EDA pretreatment was quite different due to the lack of vigorous ball-milling.

The modulus of elasticity (MOE) of birch (Betula platyphylla) wood specimens with four different moisture content (MC) levels, i.e., water-saturated, green, air-dried, and oven-dried, were examined under a low temperature condition ranging from -196 °C (liquid nitrogen temperature) to +20 °C (room temperature). Dynamic mechanical analysis (DMA) was used to evaluate the dynamic viscoelastic properties before and after the low temperature treatment, while X-ray diffraction (XRD) was used to analyze the crystalline structure. The results showed that MOE with different MC increased after the low temperature treatment. Specimens with higher MCs were more affected by the treatment than specimens with lower MCs. However, the effect of low temperature treatment (within four times) on MOE was not significant (P > 0.05). Cyclic treatments of liquid nitrogen did not decrease wood MOE. As a structural material, wood has a better residence to low temperatures compared to concrete, in which mechanical properties decreased dramatically after one cycle of low to room temperature.

It has been suggested that the Klason method overestimates the lignin content of non-wood tissues of plants. To evaluate the effect of pre-extraction treatments on lignin determination in leaves, nine kinds of pre-extraction treatment were applied to ginkgo leaves and zelkova leaves. The apparent lignin contents (lignin determination by the Klason method) of ginkgo and zelkova leaves without pre-extraction treatments were 30.7% and 42.6%, respectively. After the various pre-extraction treatments, the apparent lignin contents were still high. On the other hand, the yield of nitrobenzene oxidation products (NPs) per apparent lignin content was maintained at a very low level before and after pre-extraction treatments (maximum value was 6% for ginkgo leaf and 11% for zelkova leaf after extraction treatment) compared with the value from wood (25 to 60%). These results suggested that the Klason method overestimates the lignin content of leaves even after the pre-extraction treatments examined in this study. In addition, a considerable part of the sample from which NPs or neutral sugars originate was lost during these pre-extraction stages. These results implied that some parts of the cell wall components were also removed by these pre-extraction treatments.

Chitosan can be widely used in many areas owing to its unique properties, although its poor solubility in water is still a limiting factor. In the present study, low molecular weight chitosan (LMWC) was prepared by degradation with NaClO so that chitosan was able to dissolve in water. Chitosan to liquor ratio, NaClO content, temperature, and time were considered variables of NaClO degradation, and the Box-Behnken design was used to determine optimal conditions. There was good agreement between the experimental data and their predicted counterparts. The optimum conditions for chitosan degradation were estimated to be 1:67.91 of chitosan to liquor ratio, 22.03% of NaClO content, a temperature of 90.3 °C, and a time of 3.07 h. It was found that synthesis under these optimized conditions achieved the lowest molecular weight (10,937.4 Daltons). In addition, Fourier transform infrared spectroscopy, X-ray diffractograms, and thermogravimetric analysis showed that the structure of LMWC was similar to the original chitosan, while the crystallinity and thermal stability decreased after degradation.