Volume 14 Issue 4

Mechanical and waterproof properties were evaluated for hot-pressed cotton boards produced from different layers (3, 4, and 5) of cotton veneers under the same weight of cotton fibers and melamine-urea-formaldehyde adhesive. The mechanical and waterproof properties of cotton boards exceeded the specifications for particleboard and medium-density fiberboard of the China national standard requirements, and the four-layer cotton boards performed better. Scanning electron microscopy images showed that fibers were intertwined to form a dense network structure after hot-pressing with water, and thicker veneers were not conducive to the penetration of adhesives after cold-pressing. Fourier transform infrared spectra indicated that hydrogen bonding, physical, and mechanical bonding took place in the cotton veneers, and stronger absorption peaks were shown for the chemical functional groups of the five-layer and four-layer cotton boards. X-ray diffraction spectra revealed that the cellulose crystallinity of the cotton boards (3, 4, and 5 layers) increased to 74.5%, 74.4%, and 73.2%, respectively. Thermal gravity/ differential thermal gravity curves showed that the thinner cotton veneers of the cotton boards showed better thermal stability. These results showed promise for the revaluation of this textile waste to produce biomass composites and for its potential use as a raw material in the preparation of biomass composites.

In biomechanical analyses, computational models are essential tools for simulating the behavior of a tree subjected to a load. However, such models allow only approximation of the actual behavior of the tree if the elastic parameters of the wood in different tree parts (stem, branches, and roots) and at least orthotropic behavior are not considered. In addition, as the wood is green, the parameters of strength and stiffness must be adequate for this level of moisture. However, even for stem wood, knowledge of elastic properties is not available for most species used in urban tree planting, and this scarcity of information is even greater for wood branches. The objective of this research was to evaluate methodology, based on wave propagation, in characterizing the 12 elastic constants of wood from branches. Complementarily, compression tests were performed to characterize the strength. The obtained elastic parameters using ultrasound tests were comparable with the values expected based on theoretical aspects related to the behavior of the wood. The results of the compression test complemented the ultrasound characterization, but the application of this method for the complete characterization of the elastic parameters is not feasible for tree branches because of their small size.

Cellulose was extracted from corn stalk pith (CSP) and used for fabricating hybrid composite films with acceptable physical properties. As reinforced additives, low contents of graphene oxide (GO) and black phosphorene (BP), both ranging from 0.05 to 0.15 wt%, were separately incorporated into the cellulose matrix in a ZnCl2 aqueous system. A series of the composites were prepared via a regeneration process. The as-prepared composites showed various properties depending largely on the additive content, manner of processing, and the type of additive used. GO and BP nanosheets were homogeneously dispersed in the regenerated cellulose (RC), smoothly forming the dense films. Crystalline structures of RC-based films were revealed to be cellulose-II, and in addition to GO-crosslinked RC samples (RC-GO), an increase in the additive dosage led to a decrement in the crystallinity index of blended films (RC/GO and RC/BP). At 0.15 wt% additive amount, the RC-GO possessed superior thermal stability, tensile strength, and Young’s modulus, increasing 7.8%, 190.2%, and 79.0%, respectively, while the RC/BP exhibited a 3.5 times improvement in the elongation at break.

With the ever-increasing usage of recycled fibers, dry-strength agents play an increasingly important role in the papermaking industry. In this study, a new kind of dry-strength agent (CMS-g-PAM) was developed via grafting polyacrylamide onto carboxymethyl starch (CMS). Effects of the operation conditions, including the CMS-g-PAM dosage, polyaluminium chloride (PAC) dosage, and pH value of pulp system, on the properties of the paper were investigated. The contrasting effects when comparing the CMS-g-PAM and CMS were also researched. The results indicated that CMS-g-PAM had a beneficial effect on the paper properties. Compared to the control sample, when 1% CMS-g-PAM was added, the tensile index, burst index, and folding endurance of handsheets displayed noticeable increases of 38.2%, 34.7%, and 97.7%, respectively, and these properties were increased by 27.4%, 17.2%, and 46.6% when compared with the CMS-treated sample of this addition level. Scanning electron microscopy images showed that the bonding between fibers of the paper became tighter after using the CMS-g-PAM. The results demonstrated that CMS-g-PAM can be used as an effective dry-strength agent.

Wood-plastic composites for 3D printing from plant fiber (bleached pulp powder, mechanical pulp powder, newspaper pulp powder, eucalyptus powder, pine powder, and lignin) and polylactic acid (PLA), with silane coupling agent (KH550) as plasticizer, were prepared via melt extrusion. The physical properties, such as surface morphology, apparent density, tensile strength, melt flow rate, compatibility, and thermal stability were measured. Moreover, the effects of the content of various types of plant fiber powder in PLA on the properties of the prepared composites were investigated. The results showed that the modified lignin/PLA composite exhibited a superior performance under the same added amount. In particular, when the amount of lignin added was 15%, the tensile strength of the composite was 74.0% higher than that of pure PLA, and the melt flow rate was reduced by 17.8% compared with pure PLA. The density of the composite increased 15.8% compared with pure PLA when the lignin content was 20%. The scanning electron microscopy cross-sectional morphology and differential scanning calorimetry analyses showed that the optimal addition amount of lignin was 15%. Finally, the prepared lignin/PLA composite material was used in 3D printing with a smooth silky property and an excellent printing performance.

Four flame retardants and styrene-acrylic latex were used to make flame-retardant air filter paper via emulsion impregnation. The compositions and flame retardant mechanism of the flame retardants were investigated by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The flame retardance of air filter paper was evaluated using TGA and limiting oxygen index (LOI) meter, and the physical properties and pore structure of the flame-retardant air filter paper were measured using stiffness tester, burst tester, and aperture analyzer. The results showed that the optimal ratio of flame retardant to styrene-acrylic latex was 1:1.4. The synergistic effect of boron, phosphorus and nitrogen made FR3 have good flame-retardant effect on air filter paper. Air filter paper with FR3 also had good physical strength and suitable pore size distribution.

The dynamics and interactions of microbial communities in Paulownia’s life cycle are poorly understood. The main goal of this study was to compare the rhizospheric soil and endophytic microbiome and mycobiome of hybrid Paulownia elongata and Paulownia fortunei. The comparison was based on highly efficient Illumina MiSeq sequencing of bacteria and fungi from the rhizosphere and endosphere of bioenergetic trees P. elongata x P. fortunei. The general richness of bacteria and rhizospheric fungi (based on Chao 1, Shannon, and Simpson indicators) was higher than in endosphere samples from the same plants. Actinobacteria and Proteobacteria were dominant in the rhizosphere and endosphere of plants in healthy conditions. The rhizosphere fungal communities in both trials were dominated by Ascomycota, Mortierellomycota, and Basidiomycota. Most root endophytes came from Olpidiomycota, Oomycota, and Ascomycota, while most leaf endophytes were from Ascomycota and Basidiomycota. This study was the first report on the composition of bacteria and fungi associated with the endosphere and rhizosphere of Paulownia trees. These studies showed that bacterial and fungal communities from the rhizosphere and endosphere were separate communities. It also showed that the health conditions of trees did not affect the composition of endophytic microorganisms in Paulownia tissues.

Two dedicated biomass crops, shrub willow (Salix sp.) and miscanthus (Miscanthus giganteus), were evaluated for their ability to remove lead from contaminated water, both in raw ground form and after pretreatment by torrefaction or alkaline treatment. Sorption capacity experiments were conducted using a contaminant concentration that ranged from 1 mg to 15 mg per L and a biomass loading rate of 0.05 g biomass per mL. The results indicated that sorption capacities for the two feedstocks ranged from 0.15 mg to 0.26 mg of lead removed per gram of biomass, and the percentage of removal ranged from 54.3% to 93.6%. The sorption capacity of willow tended to decrease as particle size increased. Increasing torrefaction severity increased the sorption capacity of miscanthus, and alkaline treatment also increased the sorption capacity of miscanthus. The Langmuir isotherm, when fitted to measured data, characterized the samples’ sorption performance with a Mean Absolute Error (MAE) of 0.0014 mmol g-1.

Temperature fast-responsive and magnetic poly(N-isopropylacrylamide-co-acrylamide) (CMX-MNP-PNIPAm/Fe3O4) hydrogels were developed using carboxymethyl xylan (CMX) as a pore-forming agent and a NaCl solution as the reaction medium, followed by fabricating Fe3O4 nanoparticles in situ within the hydrogel matrix. It was found that NaCl played a role in the phase separation and was used as the electrolyte to shield CMX molecular chains. The obtained hydrogels exhibited a fast, temperature-responsive behavior, and the water retention was less than 15% for 1 min under 60 °C. The prepared hydrogels showed enhanced mechanical properties and magnetic properties due to the presence of Fe3O4 particles. The lower critical solution temperature of the hydrogels was in the range of 35 to 39 °C, which was acquired through adjusting the amount of hydrophilic monomer (AM). The magnetic and thermosensitive hydrogel had the attractive photothermal conversion ability and could be heated to 40 °C within 2 min, and to 69 °C within 7 min under near infrared irradiation.

This paper aimed to define the density fluctuations of thermally modified wood. This was achieved by the granular analysis of wood dust. The wood dust was acquired by sanding completed using a narrow belt sander. The samples were taken from spruce, oak, and meranti wood types that were thermally modified at temperatures of 160 °C, 180 °C, 200 °C, and 220 °C. The results showed the shares of ≤ 0.08 mm wood dust particles and how their share was related to the temperature treatment; residue curves manifested the wood dust stratification in individual sieves and their density. The shares and densities of the wood dust were statistically analysed, and the statistical significance of the analysed values was calculated. An increased temperature decreased the wood density and decreased the share of the ≤ 0.08 mm wood dust particles. The wood dust shares in the 0.032-mm sieve and at the bottom (the finest particles) of the sieving machine also decreased; however, the share increased in the 0.125-mm sieve.