Volume 15 Issue 3

A two-step extraction method was used to extract proteins from Caragana korshinskii Kom., including a NaOH solution extraction followed by a water extraction. A power-law model, three-site kinetic extraction model, and second-order model were utilized to investigate the mechanism of the water extraction process and the key factors affecting the protein yield. The experimental data fitted well with the three-site kinetic model, indicating that the water extraction process included washing and faster and slower stages. In addition, the slower stage was the rate-limiting step. For the water extraction process, the protein yield was increased by decreasing the particle size, increasing the NaOH concentration, or raising the extraction temperature, among which the extraction temperature was the critical factor for controlling the protein yield.

Thermal modification is widely used for bamboo materials as an efficient modification method. CO2 laser with the advantages of high energy density, short process period, non-pollution, etc. could be applied as a novel thermal treatment for wooden and bamboo materials processing. The laser intensity argumentation of power, motion arguments of feed rate, and sweep width for laser emitter were selected as input arguments for treating the Moso bamboo surface. The lightness variation and total color variation (∆L* and ∆E*) were collected using a portable colorimeter to describe the bamboo surface color variation after laser irradiation. Response surface methodology was chosen for designing experiments and modeling. The results showed that the increase of laser power had a positive influence on increasing the absolute values of ∆L* and ∆E*, but the feed rate of laser emitter and sweep width increasing had opposite effects on absolute values of ∆L* and ∆E*. The quadratic models of ∆L* and ∆E* created by response surface methodology were competent for describing the relationship between laser processing arguments and color indexes of ∆L* and ∆E*. This approach will be useful for selecting suitable and desirable processing arguments to get the surface color of bamboo productions.

Pulping spent liquor was used to hydrolyze abandoned bovine hair, and the resulting keratin hydrolyzate was blended with polyvinyl alcohol (PVOH), polyacrylamide (PAM), N,N-methylenebis (acrylamide) (MBA), and glycerol (GL) to prepare the low-cost degradable keratin-based sprayable mulch film (KSMF). The prepared KSMF contained elements required for plant growth, such as N, P, K, S, Ca, Si, and the water absorbency reached 380% in deionized water. A degradation of 23.1 wt% was attained while it was buried for 50 d in soil. The KSMF was easy to apply and needed to be diluted for spraying on the soil surface and formed a physical barrier to reduce evaporation of water and heat preservation. The KSMF had good degradability and entered the soil to become a high-quality biomass organic fertilizer during the growth of the crop, thus avoiding “white pollution” and realizing the recycling of waste, which would extend the application prospects in sustainable modern agriculture.

Bamboo is a potential non-wood lignocellulosic material from which to make particleboard. Sucrose-based adhesive is another potential ingredient, but its use in particleboard has been limited. Addition of ammonium dihydrogen phosphate (ADP) can be used to increase the bonding ability of sucrose-based adhesive and to reduce the required pressing temperature. Therefore, this research used different pressing temperatures and sucrose/ammonium dihydrogen phosphate (ADP) composition ratios to optimize the properties of particleboards. The physical and mechanical properties of the boards were analyzed and compared with the JIS A 5908 (2003) standard for particleboard. The results showed that the interaction of the sucrose-ADP composition ratio and the pressing temperature significantly affected the physical and mechanical properties of the particleboards. The particleboard using only sucrose as adhesive had optimum properties at 200 °C; however, after addition of ADP, the intended properties could be achieved at a 160 °C pressing temperature.

Ammonia-ethanol-water (AEW) pretreatment was adopted to treat wheat straw for ameliorating saccharification with the integrated preparation of submicron lignin spheres (SLS). Results showed that AEW pretreatment could remove 77% of lignin and 90% of extractives, thus increasing specific surface area and porosity of the substrate and finally enhancing the release of fermentable sugars in saccharification. Under the optimal pretreatment conditions (170 °C for 2 h, ethanol concentration 55% (v/v), ammonia concentration 7.5 wt%), the final total sugar yield reached 81.7% after pretreatment and saccharification, which was 2.25 times higher compared to the conventional ethanol organosolv pretreatment. Moreover, washing could be excluded for AEW-pretreated wheat straw before saccharification, and both ethanol and ammonia could be readily recovered and reused, making the AEW pretreatment clean and sustainable. In addition, SLS with hollow structure and average diameter of 161.2 ± 53.6 nm were fabricated using the fractionated lignin, which could offset the overall cost of AEW pretreatment.

During the embossing process, a fiber sandwich is compressed between embossing tools. The use of ultrasound causes a short-term increase in the material temperature in addition to causing plastic deformation. The combination of the material compression and an increase in material temperature leads to structural changes, which can be observed by the change in mechanical properties of the cardboard. This work investigated the influence of an ultrasonically induced temperature increase on the structural changes of cardboard. Using three-parameter combinations, different temperature levels were achieved with a material densification of less than 5%. Subsequently, the samples were subjected to selected physical and visual analyses to characterize the change in the fiber structure. With the increase of 124 ºC material temperature there was a decrease of about 15% in the splitting resistance and 10% in the bending stiffness.

Artocarpus heterophyllus (jackfruit) leaves (JL) are a waste product that is commonly used as livestock feed. Jackfruit leaves have been revealed to possess many medicinal values such as antioxidant and anti-inflammatory properties. In this study, different drying treatments (shade (SD), sun (SN), and oven (OV)) and ethanol/water ratios (E/W) were investigated to evaluate the impact on drying kinetics, color, and antioxidant properties of jackfruit leaves. Results showed that the Newton model was the best fitted mathematical model for the JL drying kinetics. The moisture effective diffusivities ranged from 2.920 × 10-10 to 6.814 × 10-10 m2/s over the temperature range studied. Shade drying was able to preserve the green pigment better than OV and SN drying treatments. Treatment with ethanol/water ratio at 80% and oven-dried (OV80) revealed the highest phenolic content (195.05 ± 1.21 mg gallic acid equivalent (GAE)/g extract weight (EW)), flavonoid content (11.02 ± 0.17 mg artocarpin equivalent (AE)/g EW), and antioxidant activities (90% scavenging activity and reducing power of 1043.84 ± 5.28 µM trolox equivalent (TE)/g EW) compared to SD and SN treatments. The OV80 also possessed the highest artocarpin, squalene, and β-sitosterol contents determined. The OV80 was selected for improving antioxidant and colour stability, and has the potential to be developed into functional biopolymer production.

This study investigated the possibility of applying flat-pressed wood-polymer composites in conditions of high humidity. The experiment involved three variants of wood-polymer composite panels 16 mm thick, and 680 kg per m3 density. The wood particles were bonded with polyethylene. The share of polyethylene in the core layer was fixed at 50%, while in the face layers the content was varied (40%, 50%, or 60%). The following parameters were examined: modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), screw holding (SH), thickness swelling (TS), water absorption (WA), susceptibility to drilling and milling, wettability and surface free energy, and resistance to mold. The results were compared to particleboard glued with urea-formaldehyde resin. The wood-polymer composite had lower MOR and MOE values and similar IB and SH values. The panels indicated a remarkably higher water resistance (lower TS and WA values) with good surface wettability and high resistance to mold fungi. Additionally, the composites were easier to machine, e.g. drilling or milling, in comparison to standard particleboards.

Oxidized starch (OS) adhesives with a balance between their adhesion and disintegration properties were prepared by controlling the degree of oxidation and modifying the cross-linker type and level to replace urea-formaldehyde (UF) resins for easy recycling of medium density fiberboard (MDF). Four molar ratios of H2O2/starch, two types of cross-linker, i.e., blocked-pMDI (B-pMDI) and citric acid (CA), and three levels of the cross-linkers were employed to tailor the performance of the OS adhesives. The OS reacted with the isocyanate groups from the B-pMDI to form amide linkages, while it formed ester linkages by reacting with the CA. The resulting B-pMDI/OS-bonded MDF had better physical and mechanical properties than the CA/OS-bonded MDF, with comparable adhesion (0.34 MPa) to UF resins and ten times greater degree of fiber disintegration than UF resins. The combination of a 0.5 molar ratio OS with 7.5 wt% of B-pMDI produced MDF exhibiting an optimal balance between adhesion and disintegration, suggesting that such OS adhesives could someday replace UF resins in manufacturing and recycling of MDF without formaldehyde emission.

To evaluate the effects of chemical changes during thermal modification on the resistance of wood against photodegradation, heat-treated specimens of rubber wood (Hevea brasiliensis) were exposed to ultraviolet light for 384 h. The color changes in the exposed wood surfaces were analyzed using a colorimeter; the chemical changes were monitored using Fourier-transform infrared spectroscopy (FTIR). The photoweathering performances of rubber wood treated at 155 °C for 2 h, 155 °C for 6 h, and 185 °C for 2 h were similar to that of untreated wood, as the lignin did not undergo profound chemical transformation under mild modification conditions. However, compared to untreated rubber wood, the photoaging performances of rubber wood treated at 185 °C for 6 h and 215 °C for 2 h were notably changed. The transformation process was confirmed by FTIR. A good linear relationship between color change and lignin degradation was observed after mild, but not severe, heat treatment. The concentration of carbonyl groups in the wood specimens generally increased during photoaging, although not all samples showed a good correlation between color change and the concentration of carbonyl groups. Only the photochromic performance of wood changed notably when lignin was extensively modified under severe heat-treatment conditions.