Water Resistance Performance Research Articles

Mechanical and water resistance performance of physically cross-linked poly(vinyl alcohol) composite with poly(dopamine) modified cellulose nanocrystals

A novel strategy was developed for the construction of physically cross-linked poly(vinyl alcohol)- PVA composite reinforced by poly(dopamine) modified cellulose nanocrystals (PDA@CNCs) with robust mechanical and water resistance property. The PDA@CNC hybrid had improved thermal stability and the rod-like morphology of CNCs was well preserved after the PDA modification. The Young’s modulus, tensile strength and water resistance property of physically cross-linked PDA@CNC/PVA composites were obviously improved compared with the composites without cross-linking. The improved properties of the PDA@CNC/PVA composites were attributed to the destruction of intramolecular hydrogen bond and reconstruction of intermolecular hydrogen bonds as well as ferric ions coordination cross-linking interactions. The excellent mechanical and water resistance property of the developed PDA@CNC/PVA provides a path way for the development of water induced-mechanically adaptive PDA@CNC functional nanocomposites for applications such as direct ink writing in 3D/4D printing.

Thermal and chemical modification of wood – a combined approach for exclusive, high-demanding performance products

ABSTRACT Chemical and thermo-chemical modification processes were applied to European beech wood to make it applicable for interior applications which place high demands on aesthetics, hygrothermal and water resistance performance. In particular, the use of modified wood in kitchen tools was foreseen. Impregnation modification with a 20% DMDHEU solution, thermal modification and a combined approach of thermo-chemical modification were compared. All modification processes caused a darkening that for the high modification intensities became close to the aesthetics of some of the most renowned tropical hardwood species. The higher the modification intensity, the higher the improvement. In particular, chemical and thermo-chemical modification processes significantly decreased the liquid water uptake. As regards the mechanical performances while stiffness and strength did not change abruptly and hardness increased, the resistance towards dynamic impacts significantly decreased with every kind of modification process. Thermo-chemical modifications resulted to be an interesting way to improve most of the physical properties of wood with outstanding behaviour in terms of colour appearance and reduction of water uptake in wet environments. An increased brittleness is the weakest point for foreseen fields of application.

Effect of zein subunit and plasticizer on rheology and adhesion properties of zein-based adhesives

Protein-based adhesives have received widespread attention due to their low-cost, resourcefulness, ecofriendliness. Here, an easy and quick preparation of zein adhesive was introduced. Under the plasticizing action of the plasticizer (acetic acid or ethanol), amorphous zein powder changed from solid particles to sticky and flowing state, and then formed zein-plasticizer adhesive with great adherence. During this transition, the aggregates of zein molecules were destroyed by the lubricative effect of plasticizer, and α-helix structures of zein increased by the protonation of zein in acetic acid, but decreased due to the hydrophobic interaction caused by ethanol. Zein-plasticizer adhesive was mainly composed of non-covalent ‘physical’ cross-links. The zein-plasticizer adhesive containing stronger plasticizer got higher flowability and longer solidifying time. And stronger plasticizer also led to greater thermal stability, more stable structure and smoother surface for solidified zein-plasticizer adhesive, which resulted in stronger adhesion strength and greater water resistance. The ɑ-zein was easier to be plasticized than β- and γ-zein, and the plasticizing ability of acetic acid was stronger than that of ethanol. The α-zein-acetic acid adhesive therefore showed outstanding performance in adhesion strength (600 kPa) and water resistance (300 kPa) among all zein-plasticizer adhesives, and has wide application as a promising waterproof adhesive. • Zein can form adhesive with great adherence under the action of plasticizer. • Zein-plasticizer adhesive was composed of non-covalent ‘physical’ cross-links. • The degree to which the zein was plasticized determined its adherence. • The adhesion of α-zein-acetic acid adhesive was 600 kPa in dry and 300 in wet.

Editorial: Special Issue on Smart and Green Infrastructures with Optimum Life Cycle Solutions

Editorial: Special Issue on Smart and Green Infrastructures with Optimum Life Cycle Solutions

Physically Cross-linked nanocellulose composites tailored from base bath and ferric (III) ion: Mechanical, water resistance and thermal property

The development of sustainable composites from wood derived cellulose nanocrystals (CNCs) and degradable poly(vinyl alcohol)-PVA polymer is a promising strategy to resolve the issue of plastic pollution, which is also consistent with the current carbon neutrality and sustainable development tendency. However, the strong intra- or inter-molecular hydrogen bonding interactions of CNCs endow it with poor processability, resulting in the composites with unsatisfied comprehensive performance. Therefore, a novel method developed from base bath solutions and ferric (III) ion was reported to construct the physical cross-linking (e.g., hydrogen bonding and coordination interactions) to improve the water resistance, thermal and mechanical performance of PVA/CNC composites. For the comparison with the counterparts without cross-linking, the Young’s modulus and tensile strength of physically cross-linked PVA/CNC composites were obviously increased. Meanwhile, the thermal and water resistance property of physically cross-linked composites was also obviously improved owing to the physical interactions, e.g., hydrogen bonding and ferric (III) ion-carboxyl group coordination interactions. The results above provided the basis for the further exploration of direct ink writing 3D/4D printing sustainable nanocellulose composites.

Microanalytical characterizations, mechanical strength and water resistance performance of solidified dredged sludge with industrial solid waste and architecture residue soil

Industrial solid waste (slag, desulphurization gypsum, fly ash) and construction soil architecture residue soil are used to solidify dredged silt to develop a novel cover material. Through the application of shear, compressive, and permeability tests, shear strength parameters, unconfined compressive strength, volume shrinkage and hydraulic conductivity of the cured silt were assessed under the different curing times and wet-dry cycles conditions. The result shown slag played the most significant role in the silt consolidation process, followed by FGD gypsum and fly ash. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and nuclear magnetic resonance (NMR) detection methods were employed to determine the hydration products, chemical characteristics, microscopic morphology and pore structure of the solidified sludge, and identify the solidification mechanisms of the industrial waste and slag. After the wet and dry cycles, micropores and foramen (0.1–0.5 µm) continued to dominate pores, accounting for 64–76 % of pore space. Hydration products in the solidified sludge primarily consisted of C-S-H, C-A-S-H, and N-A-S-H gelled products, along with ettringite and zeolite.

K2SiF6:Mn4+ significantly improves water resistance and luminescence performance by coating green emission graphene quantum dots

In order to enhance the luminescent thermal stability and water resistance of K2SiF6:Mn4+, we proposed a simple hydrothermal method to synthesize K2SiF6:0.06Mn4+@GE-GQDS (6 mg/mol) (GE-GQDs: green emission graphene quantum dots) red emitting phosphor with outstanding water resistance. The emission intensity of the sample coated with the GE-GQDs still maintains 87.74% of the initial one after immersion for 360 min, while the uncoated K2SiF6:0.06Mn4+ sharply decreases to 11.26%. Another impressive phenomenon is that due to the negative thermal quenching (NTQ) effect, the luminescent thermal stability of the coated sample is also significantly improved, and the integrated photoluminescence (PL) intensity at 180 °C is 238% of that at 25 °C. In the meantime, the integrated PL intensity of the coated samples is 2.55 times that of K2SiF6:0.06Mn4+ under room temperature. Based on experimental results, it is suggested that after coating with GE-GQDs, a surface protective layer is formed on the surface of the sample, which improves the water resistance, room temperature emission intensity, and luminescent thermal stability of the coated sample. Finally, the improvement mechanism of the above multiple enhancements on luminescent properties is discussed and proposed. The above multiple enhancement effects make the sample have broad application for blue light-based warm and high-power WLEDs (white light-emitting diodes).

Study on the mechanical properties of modified rammed earth and the correlation of influencing factors

The main ingredients of traditional rammed earth walls are plain soil, which decreases the compressive strength and water resistance performance of the rammed earth buildings. To promote the application of rammed earth in traditional buildings, varying additional materials were added to modify the rammed earth, and the water stability and compressive strength of modified rammed earth were investigated. Firstly, the plain soil in Northwest Sichuan was selected as raw material, and seven groups of modified rammed earth standard specimens were fabricated by mixing cement, fiber, sand and gravel or soil stabilizer. Then, the compressive strength tests, water stability tests, and splitting tensile strength tests were performed. After the tests, the failure modes, load displacement curves, compressive strength, and splitting tensile strength of the specimens are analyzed. Furthermore, the correlation between varying parameters and compressive strength, water absorption, and splitting tensile strength of specimens are studied, and the micro mechanism of modified rammed earth is discussed. It indicates that the porosity of the modified rammed earth is reduced and generates a more compact and stable microstructure, which improves the compressive strength, water stability and splitting tensile strength of the modified rammed earth. The hydration products generated by the cement hydration process wrap and connect the soil particles, which fill the gap between the soil particles. By performing variance and correlation analysis, it is found that the variation of fiber types had significant effects on water-saturated compressive strength, water absorption，and compressive strength, and the corresponding correlation coefficients are 0.766， −0.701，and 0.534，respectively. By performing value analysis, SN5 (mixed 8% cement + 20% sand +20% gravel + 0.05% polypropylene fiber) exhibits the better mix proportions and the lower cost.

Superamphiphobic coatings with subambient daytime radiative cooling—part 1: Optical and self-cleaning features

Waterborne and solvent-based coatings with prominent passive subambient daytime radiative cooling (RC) coatings were fabricated to conserve cooling energy in the summer. Concurrently, water- and alcohol-based superamphiphobic self-cleaning coatings were manufactured and introduced into the RC coatings as topcoats. The contact angles of water and n-hexadecane of the superamphiphobic topcoat containing coating systems were 163.4° and 151.4°, respectively; additionally, the sliding angles of water and n-hexadecane of these systems were 2° and 9°, respectively. Moreover, the introduction of a transparent superamphiphobic topcoat to the RC coatings did not affect their originally high solar reflectance but improved their emissivity values in the atmospheric transparency window, wavelengths between 2.5 and 24 μm, and the entire infrared spectrum due to the presence of plenty of silicon-oxygen bonds formed via hydrolysis and/or alcoholysis reactions and the subsequent co-polycondensation of tetraethoxysilane and 1H,1H,2H,2H-perfluorodecyltriethoxysilane. The solar reflectance of the coating system was 0.986, which is the highest recorded worldwide. The emissivity of the superamphiphobic RC coatings in the atmospheric transparency window was 0.954. The superamphiphobic RC coatings possessed excellent static and dynamic non-wetting capabilities, significantly improving their water resistance, waterproofing properties, and anti-graffiti performance. Additionally, the superamphiphobic RC coatings exhibited outstanding self-cleaning properties, preventing the coating surfaces from being contaminated by dust, soiling, grime, and water/oil-soluble pollutants, thereby enabling them to maintain an extremely high solar reflectance.

High-performance water vapor barriers via amorphous alumina-polycrystalline zinc oxide hybrids with a self-wrinkling morphology

This work presents a materially and structurally designed barrier thin film with a self-wrinkling morphology, which consists of composites of amorphous alumina (a-Al2O3) and polycrystalline zinc oxide (ZnO). The pure ZnO, Al2O3 films, and Al2O3-ZnO composited film are deposited on polyethylene terephthalate (PET) by magnetron co-sputtering at room temperature. The water vapor transmission rate (WVTR) for the composited film with about 30 % ratio of Al2O3 to ZnO is down to 0.026 g·m−2·day−1 from 1.184 g·m−2·day−1 of pure ZnO film at 38 °C/90 % RH, indicating that the nanocomposite structure of amorphous Al2O3 and crystalline ZnO can significantly improve the water-resistance performance. Theoretical calculations demonstrate that the amorphous Al2O3 can dramatically suppress the defect fraction within ZnO from 4.65 % to 0.08 %. Furthermore, a self-wrinkling morphology with Al2O3-ZnO composited film deposited on PET/acrylic is designed to have the WVTR value as low as 1.30 × 10−3 g·m−2·day−1. Due to the stress release when forming micro-scale wrinkles, the more smooth and dense Al2O3-ZnO composited film can markedly sharpen up the barrier property. The low WVTR barriers via amorphous and crystalline hybrid composites with self-wrinkling morphology by magnetron sputtering potentially serve as a low-cost and large-scale production path for electronics encapsulation as compared to atomic layer deposition (ALD) and plasma-enhanced chemical vapor deposition (PECVD).

Preparation of a Novel Carbon Dot/Polyvinyl Alcohol Composite Film and Its Application in Food Preservation.

Carbon dots (CDs) were synthesized with the facile hydrothermal method to produce CDs/polyvinyl alcohol (PVA) active food packaging films. The CDs had a diameter ranging from 2.01 to 5.61 nm and were well-dispersed. The effects of different concentrations of CDs on mechanical strength, water resistance, morphology, optical, and thermal performance of the CDs/PVA films were discussed. The incorporation of CDs in the PVA film improved its mechanical properties, water resistance properties, UV blocking properties, and thermal stability and endowed the composite film with antioxidant and antimicrobial properties. The maximum scavenging rates of 2,2-diphenyl-1-picrylhydrazyl and ABTS free radicals by the 0.50% CDs/PVA film were 72.81 and 97.08%, respectively. The inhibition zone diameters of the 0.50% CDs/PVA solution against Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), and Escherichia coli (E. coli) were 9.52, 8.21, and 9.05 mm, respectively. Using the 0.50% CDs/PVA film as active packaging, the shelf life of banana, jujube, and fried meatballs was observed to be extended significantly. These results demonstrate the viability of the CDs/PVA composite film as a promising active food packaging material.

Water-resisting performances and mechanisms of magnesium phosphate cement mortars comprising with fly-ash and silica fume

Design of hydraulic structures using magnesium phosphate cement (MPC) composites is a still challenging issue because of the volume instability of MPC matrices in water environment. In this research, an attempt was taken to progress the water-resistance performance of MPC blended with fly ash (FA) and silica fume (SF). The FA was introduced as one third of magnesia in the mortar specimens, where SF dosages were 5%, 10% and 15% as the substitution of magnesia. Physico-mechanical and microstructural properties of mortar samples were examined considering the air and water curing systems. The analytical results bared that compressive strength (CS) and flexural strength (FS) of specimens composed with MPC + FA+5%SF were observed about 25% higher as compared to control. Both strength properties having the optimized content of SF (i.e. 5%) was reduced close by 3–4% in water system, whereas the pure MPC matrix exhibited around 20% less at 28 d. In addition, mass loss (ML) was found nearby 1.56% at 28 d. Moreover, SEM, EDS and XRD tests were detected that intermediate minerals namely Berlinite, Mullite, Lizardite and Enstatite were formed in the microstructures, and micro-cracks and micro-pores were significantly reduced. Consequently, compact microstructure was obtained that resulted the well water-resistant of proposed MPC mortar. The outcomes of this research might be a potential information for constructing the MPC-based water structures.

It is still too early to promote biodegradable mulch film on a large scale: A bibliometric analysis

Biodegradable mulch film was considered to be a sustainable ecological alternative alleviate of plastic mulch film. Extensive studies related to biodegradable mulch film have been carried out in multiple perspectives. However, there was no systematic synthesis of the studies because of the complex research subjects, diverse research contents, and plentiful research perspectives in this field. In the present study, a bibliometric analysis was applied to analyze the evolution and current status of the research about biodegradable mulch film, so as to reveal research hotspots and predict future trends. The research about biodegradable mulch film had developed from a field concentrated on material development to multi-disciplinary field with three main research knowledge bases: the necessity of degradable mulch film application, mulching on crop production and degradation process of biodegradable mulch film. The study hotspot has shift from development of biodegradable materials to farmland application of the biodegradable mulch film. The ecotoxic of degradation process and degradation products especially for microplastics of biodegradable mulch film on soil environment was getting the attention of scientists. Based on these findings and status quo, three research directions including development of renewable biodegradable materials with higher water resistance performance, farmland suitability evaluation of biodegradable mulch film and safety evaluation of farmland soil with biodegradable film mulching. It is still too early to apply biodegradable mulch film on a large scale because its potential ecotoxicity to soil environments is not identified yet.

Enhanced Water Resistance and Catalytic Performance of Ru/TiO2 by Regulating Brønsted Acid and Oxygen Vacancy for the Oxidative Removal of 1,2-Dichloroethane and Toluene.

The compositions of volatile organic compounds (VOCs) under actual industrial conditions are often complex; especially, the interaction of intermediate products easily leads to more toxic emissions that are harmful to the atmospheric environment and human health. Herein, we report a comparative investigation on 1,2-dichloroethane (1,2-DCE) and (1,2-DCE + toluene) oxidation over the Ru/TiO2, phosphotungstic acid (HPW)-modified Ru/TiO2, and oxygen vacancy-rich Ru/TiOx catalysts. The doping of HPW successfully introduced the 1,2-DCE adsorption sites to promote its oxidation and exhibited outstanding water resistance. For the mixed VOCs, Ru/HPW-TiO2 promoted the preferential and superfluous adsorption of toluene and resulted in the inhibition of 1,2-DCE degradation. Therefore, HPW modification is a successful strategy in catalytic 1,2-DCE oxidation, but Brønsted acid sites tend to adsorb toluene in the mixed VOC oxidation. The Ru/TiOx catalyst exhibited excellent activity and stability in the oxidation of mixed VOCs and could inhibit the generation of byproducts and Cl2 compared with the Ru/HPW-TiO2 catalyst. Compared with the Brønsted acid modification, the oxygen vacancy-rich catalysts are significantly suitable for the oxidation of multicomponent VOCs.

In-situ construction of carbon-doped ZnO hollow spheres for highly efficient dimethylamine detection

Pure ZnO and carbon-doped ZnO hollow spheres were successfully synthesized by a hydrothermal-calcination process. The doping content of carbon in ZnO was controlled by different calcination temperatures at 500 ℃ and 600 ℃ (named as ZnO-500 and ZnO-600). Systematic material characterization indicates that mesoporous ZnO hollow spheres are featured in abundant defects induced by in-situ carbon doping. Used as gas sensing materials, the response of ZnO-600 towards 200 ppm dimethylamine (83.6) is 28.6 times and 2.5 times higher than that of Pure ZnO (2.9) and ZnO-500 (32.8) at the optimum operating temperature of 240 ℃. Remarkably, the response of ZnO-600 toward 1 ppm dimethylamine is as high as 7.2, and simultaneously the limit of detection is as low as 108 ppb. In addition, ZnO-600 hollow spheres hold excellent gas-sensing performance in response-recovery speed, selectivity, repeatability, long-term stability, and water resistance towards dimethylamine. The boosted dimethylamine sensing performance of ZnO-600 is mainly attributed to synergistic effects of the unique mesoporous microstructure and rich defects induced by in-situ carbon doping. This work provides a promising material for dimethylamine detection, the properties of which can be improved for practical applications in the future. Furthermore, this contribution gives new insights into nonmetal-doped metal oxide nanostructures for high-performance gas sensors via surface defect control.

Influence of polymerizable surfactants on the adhesion performance and water resistance of water-based acrylic pressure-sensitive adhesives (PSAs)

The behavior of different polymerizable surfactants was investigated to improve the water-resistance of pressure-sensitive adhesives (PSAs) based on acrylic acid (AA) and n-butyl acrylate (n-BA). Differences in the adhesion properties were found according to the chemical structure and the critical micelle concentration of the polymerizable surfactant, especially when compared to the non-polymerizable reference surfactant (Dowfax 2A1). The polymerizable surfactants with a branched structure resulted in more gel content and higher glass transition temperature in the adhesive. In general, the peel resistance and tack properties decreased with the use of polymerizable surfactants in the PSA formula. However, increased shear resistance was observed with respect to the PSA adhesive synthesized with the reference surfactant. Furthermore, the adhesives made with higher molecular weight polymerizable surfactants resulted in higher shear elastic modulus, shear strength, and deformation energy than the rest of the PSA adhesives. On the other hand, as expected, all the polymerizable surfactants studied contributed to the improved water resistance of the PSA compared to the reference PSA prepared with a conventional surfactant. The covalent bond formed between the polymer and the surfactant limited the migration of the surfactant towards the air-film interface thus reducing the formation of water entry pathways. The polymerizable surfactants with linear molecular structure showed the best water resistance performance.

Development and characterisation of sugarcane bagasse nanocellulose/ PLA composites

ABSTRACT Nanocellulose from sugarcane bagasse fibres was isolated via chemo-mechanical method subjected to preparation of its PLA-based bionanocomposites using an Injection moulding process with varying weight percentages of nanocellulose. The mechanical properties (i.e. tensile, flexural, fracture toughness, and impact), thermal property (TGA analysis) and dynamic mechanical properties (i.e. storage modulus, loss modulus, and damping) of the prepared bionanocomposites were studied. In addition, water absorption behaviour in terms of maximum water uptake and sorption, diffusion and permeability coefficients of the bionanocomposites were also investigated. Anoticeable improvement in thermal stability, water resistance, and mechanical performance was seen in bionanocomposites with 2 wt. % of nanocellulose. There were 41.44%, 26.21%, 89.79%, and 16.38% improvements in tensile strength, flexural strength, fracture toughness and impact strength, respectively, for 2 wt. % of nanocellulose reinforcement composite over neat PLA matrix. ANOVA analysis was also performed and found that contents of nanocellulose have asignificant impact on the mechanical properties of the bionanocomposites.

N-doped carbon-modified palladium catalysts with superior water resistant performance for the oxidative removal of toxic aromatics

The supported palladium catalysts perform well in the oxidative removal of hazardous aromatic hydrocarbons. However, water vapor can seriously deactivate the catalysts especially in the low-temperature regime. Hence, improving moisture resistance of the Pd-based catalysts is full of challenge in the removal of aromatics. Herein, we report a new type of Pd@NC/BN catalysts featured with nitrogen-doped carbon layers modified Pd supported on hexagonal boron nitride (h-BN), and the relationship between structure and water resistance of the catalysts. The results show that in the presence of 10 vol% H2O in the feedstock, the Pd@NC/BN catalyst could effectively oxidize o-xylene (with an almost 87% removal efficiency), whereas o-xylene conversion declined from 69% to 20% over the conventional Pd/Al2O3 at a reaction temperature of 210 °C and a space velocity of 40,000 mL/(g h). The adsorption of H2O was significantly inhibited on the nitrogen-doped carbon layers due to the hydrophobic nature. Meanwhile, the oxygen species active for o-xylene oxidation were not only from the adsorbed gas-phase oxygen but also from the new active oxygen (*OOH and *OH) species that were generated via the interaction of O2 and H2O in the presence of water in the feedstock. It is concluded that the reactive oxygen species that accelerated the activation and cleavage of C−H bonds significantly facilitated the conversion of key intermediate species (from benzaldehyde to benzoic acid), thus playing a decisive role in o-xylene oxidation. The present work provides a direction for developing the superior water resistance catalysts with hydrophobic nature and good water activation ability in the oxidative removal of volatile organic compounds.

Experimental Investigation on Post-Peak Permeability Evolution Law of Saturated Sandstone under Various Cyclic Loading–Unloading and Confining Pressure

The permeability evolution law of saturated rock under cyclic loading–unloading after shear yield is an important basis for revealing the water resistance performance and water inrush risk of overlying rock under multiple mining conditions. In this paper, the influence of the confining pressure, the cyclic loading–unloading times (CLT), and the volumetric strain on the post-peak permeability of saturated sandstone was studied by carrying out a post-peak permeability experiment. Based on SEM images and an improved simulated annealing algorithm, the 3D internal structure characteristics of sandstone samples before and after the experiment were reconstructed. The influences of the confining pressure on pore diameter, effective porosity, connectivity, seepage path length, and tortuosity of the sandstone before and after the experiment are discussed. Research results indicated that (1) In the post-peak cyclic loading–unloading stage, the volumetric strain is negatively correlated with permeability. At the unloading and initial loading stage, the volumetric strain showed a gradually decreasing trend as the specimen was slowly compressed. However, at the middle and final loading stages, the volumetric strain curve shifted to the left and showed a decreasing trend, resulting in an obvious increase in permeability. (2) The influence of CLT on k is closely related to the confining pressure level. When the confining pressure changed from 4 MPa to 12 MPa, the volumetric strain–average stress hysteretic curve shifted to the left in turn and the corresponding permeability gradually increased. When the confining pressure increased to 16 MPa and 20 MPa, the volumetric strain–average stress hysteretic curve shifted to the right in turn and the corresponding permeability showed a decreasing trend. No matter what the value of CLT, the magnitude of sandstone permeability gradually decreased and the decreasing trend became flat as the confining pressure increased, especially for σ3 = 16 MPa and 20 MPa. (3) No matter what value of the confining pressure, the hysteresis area of the first cycle was larger than that of last three cycles, indicating that the plastic deformation generated in the first cycle was larger than that generated in the last three cycles and the recovery rate of the permeability increased with an increase of CLT. (4) As the confining pressure gradually increased, the pore diameter, effective porosity, and connectivity all approximately showed a linear decrease due to more easily compacted pores and cracks under high confining pressure, lower connectivity, and permeability, while the length and tortuosity of the seepage path increased nonlinearly, roughly due to a more significant shear failure phenomenon where the seepage path became more tortuous, that is, the greater the tortuosity, the longer the seepage path. The research results can provide an important theoretical basis for water resistance performance and water inrush risk assessment of overlying aquifer under the influence of mining stress.

Fabrication and characterization of soybean straw and polylactide acid-based hybrid bio-board

Biodegradable bio-board is held together by the self-bonding ability of natural fibre rather than by the synthetic resin adhesives used in traditional fibreboard. This provides a promising way to reduce the use and release of toxic substances. However, the hydrophilic characteristic of natural fibres gives bio-board poor water resistance compared to conventional fibreboards. Therefore, the objective of this study was to fabricate a hybrid bio-board in a wet forming process using soybean straw fibre with polylactic acid (PLA) added as a binder at different mass percentages. The effects of applied pressure during fabrication on the mechanical properties, water resistance properties, and wettability of hybrid bio-board were investigated. The thermal stability, spectroscopic characteristics, and morphological properties were also analysed. The addition of PLA weakened the bending strength and tensile strength of the hybrid bio-board made at each of three applied pressure levels. Fortunately, the hybrid bio-board with 10 and 30% PLA contents could maintain a considerable bending strength higher than 35 MPa when made with 8 MPa of applied pressure. The addition of PLA greatly improves the water-resistant performance of the board. Even with only 10% PLA, the water absorption and thickness swelling rates were reduced by more than half. We argue that PLA could be utilized as a latent natural binder to make hybrid bio-board using agricultural straw fibre; however, an environmentally friendly coupling agent is needed to improve the mechanical properties.