Expansive soil, characterized by significant swelling-shrinkage behavior, is prone to cracking under wet-dry cycles, severely compromising engineering stability. This study combines experimental and molecular dynamics (MD) simulation approaches to systematically investigate the improvement effects and micromechanisms of polyvinyl alcohol (PVA) on expansive soil. First, direct shear tests were conducted to analyze the effects of PVA content (0 %-4 %) and moisture content (30 %-50 %) on the shear strength, cohesive force, and internal friction angle of modified soil. Results show that PVA significantly enhances soil cohesive force, with optimal improvement achieved at 3 % PVA content. Second, wet-dry cycle experiments revealed that PVA effectively suppresses crack propagation by improving tensile strength and water retention. Finally, molecular dynamics simulations uncovered the distribution of PVA between montmorillonite (MMT) layers and its influence on interfacial friction behavior. The simulations demonstrated that PVA forms hydrogen bonding networks, enhancing interlayer interactions and frictional resistance. The improved mechanical performance of PVAmodified soil is attributed to both nanoscale bonding effects and macroscale structural reinforcement. This study provides theoretical insights and technical support for expansive soil stabilization.

The application of coating materials to regulate nitrogen release is a crucial strategy for minimizing fertilizer loss and alleviating agricultural nitrogen pollution. However, it remains a significant challenge to develop ecofriendly coatings that are both biodegradable and effective in slow-release. In this study, Ca/Al layered double hydroxides (LDHs) were incorporated into a conventional polyvinyl alcohol/polyvinylpyrrolidone (PVA/ PVP) matrix to create PVA/PVP-LDHs composite films. The inclusion of LDHs (1.0 %, w/w) resulted in a 32 % enhancement in water resistance, a 10 % reduction in water vapor/ammonia permeability, and a 16 % improvement in mechanical properties. These enhanced performances by addition of LDHs were attributed to the combined effects of the tortuous diffusion pathways, and the formation of robust hydrogen bonding networks between the hydroxyl groups of LDHs and PVA/PVP at the organic-inorganic interface. These interactions could reduce free hydroxyl groups on the film surface, leading to hydrophobicity and structural integrity. The composite films exhibited significantly reduced nitrogen permeability under various pH conditions, indicating the improved stability in both acidic and alkaline soil environments. Degradation experiments revealed that the composite film lost 40 % of its mass over 120 days, with a half-life only 8.0 % longer than pure PVA/PVP. These results indicated that the incorporation of LDHs had minimal impact on biodegradability, maintaining the environmental compatibility of the films. These findings highlight the potential of PVA/PVP-LDHs composite films as sustainable, eco-friendly, and efficient slow-release fertilizer coatings, offering a practical solution for improving nitrogen use efficiency and reducing agricultural nitrogen pollution.

Mulching films serve various functions, such as temperature regulation, moisture retention, and weed suppression. They can substantially increase crop yields and are widely adopted in agricultural practices. However, the use of traditional plastic mulch films is limited by their difficult recycling processes and poor biodegradability, leading to soil contamination and negatively affecting crop growth. Consequently, eco-friendly alternatives are gaining attention as replacements for conventional petroleum-based films in agricultural applications. Enhancing the performance of these eco-friendly films remains a crucial challenge. Traditional polyvinyl alcohol (PVA) films have inherent limitations, including low mechanical strength and poor water resistance. In this work, a PVA/sodium alginate (SA)/glycerol (GLY)/glutaraldehyde (GA) film was prepared that is biodegradable, demonstrates superior mechanical properties, and offers exceptional transparency through glutaraldehyde crosslinking. The impact of GA on films was examined using characterization techniques. The findings revealed that the composite film has a uniform, compact surface with no observable holes or aggregation. The mechanical performance and water vapor barrier properties (WVP) of the film were significantly enhanced after GA crosslinking. The tensile strength and elongation at the break of the PVA/SA/GLY/GA film reached 33.73 MPa and 362.89%, respectively. This work offers a straightforward approach to the development of sustainable agricultural materials.

The growing significance of biodegradable plastics for environmental protection underscores the need to enhance their performance of degradation in natural environments. This study prepared PLA/PVA blends with varying ratios to assess the impact of PVA on their thermal properties, mechanical properties, and degradation behavior. Results indicated that as the PVA content increased from 0 to 100%, both tensile and flexural strengths initially decreased before increasing. Furthermore, the decomposition temperature of the blends decreased by 18-35 degrees C as the PVA content increased. Specifically, pure PLA exhibited a thermal degradation temperature of 332 degrees C; while, the blend with 80% PVA showed a reduced temperature of 296 degrees C. Hydrolysis tests showed that weight loss increased significantly with higher PVA content, with the 20PLA/80PVA blend losing 78.9% of its weight after 30 days, compared to only 0.13% for pure PLA. The mechanical properties of the 20PLA/80PVA blend decreased by 98.31% in tensile strength and 79.19% in hardness after 30 days of hydrolysis, demonstrating accelerated degradation. Soil degradation tests further revealed that the 20PLA/80PVA blend lost over 85% of its weight within 20 days; while, pure PLA lost less than 1%. These results suggest that altering the PLA/PVA ratio can substantially enhance degradation rates, offering valuable insights for the development of efficient biodegradable plastics.

Earthen sites of substantial significance have experienced considerable degradation. Chemical stabilization is a commonly used restoration technique, and temperature effects are a critical factor for this degradation, particularly for outdoor sites. However, significant gaps exist in research on the threats posed to stabilization materials by elevated temperatures. Therefore, this study investigates polyvinyl alcohol (PVA) as a representative organic stabilizer to examine the effects of temperature variations from 20 degrees C to 400 degrees C on mechanical properties and microstructure of PVA-stabilized soil. A combination of macro- and micro-scale characterization techniques, alongside theoretical modelling, is employed. The results show that constitutive models inspired by concrete effectively characterize the stress-strain behavior of PVA-stabilized soil under high-temperature conditions. Unconfined compressive strength of PVA-stabilized soil significantly decreases from 0.90-2.25 to 0.17-0.40 MPa as the temperature increases from 200 degrees C to 300 degrees C, which is attributed to structural changes of soil induced by thermal decomposition of PVA. The thermal degradation of PVA can generate harmful gases and cause a significant colour change. Therefore, organic materials like PVA are suitable for the restoration of earthen sites in non-fire-risk areas. However, caution is necessary when applying these materials in earthen sites at risk of fire hazards, especially those with vegetation cover.

This study focused on synthesizing polyvinyl alcohol (PVA) utilizing glutaraldehyde (GA) as a crosslinking agent and silicon dioxide (SiO2) nanopowder with titanium dioxide (TiO2) nanopowder to reduce or prevent the hydrophilic property of PVA. Integrating SiO2 and TiO2 into the PVA boosted the hydrophobicity, thermal properties, and self-cleaning of the PVA film. The characteristic properties of PVA/GA, PVA/SiO2/GA, and PVA/SiO2/TiO2/GA nanocomposites polymer membranes were investigated by gel content, swelling capacity, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction patterns (XRD), scanning electron microscope (SEM), thermal gravimetric analysis (TGA), and contact angle. The resulting PVA/5%SiO2/1%TiO2/GA nanocomposite exhibits much better physical properties than PVA/GA hydrogel (water absorbency from 3.1 g/g to 0.07 g/g and contact angel from 0 degrees to 125 degrees). In addition, the nanocomposite retains very low swelling properties. These prepared nanocomposites are promising in a variety of applications such as sand soil stabilizers, construction, and building works where they exhibit excellent water resistance performance. This study introduces a novel approach for creating hydrophobic polymeric membranes from hydrophilic polymeric materials to stabilize sandy soil effectively.

Conventional biochar-based fertilizers, which typically consist of a mixture of biochar, chemical fertilizers, and additives, offer benefits but often exhibit rapid nutrient release, limiting their long-term effectiveness. Herein, we explored the enhancement of slow-release performance in biochar-based compound fertilizers by incorporating a kaolinite-infused polyvinyl alcohol/starch (K-PVA/ST) coating, resulting in a new formulation denoted as KPVA/ST-BCF. The results demonstrated that, compared to traditional NPK fertilizers, nitrogen leaching from KPVA/ST-BCF in soil column leaching tests was reduced to 19.1 % over 29 days, while phosphorus and potassium leaching were reduced to 48.5 % and 72.3 %, respectively. Mechanistic investigations revealed that the inclusion of kaolinite in the PVA/ST matrix reduces swelling, improves water retention, and enhances mechanical properties, leading to a more gradual and sustained release of nutrients. Field trials on reclaimed land showed that KPVA/ST-BCF increased wheat yield by up to 100 % compared to conventional NPK treatment. It also enhanced soil nitrogen content and organic matter, with organic matter reaching 22.7 g/kg at grain maturity. The economic assessment indicated that despite higher initial production costs compared to conventional NPK fertilizers, K-PVA/ST-BCF offers higher nutrient use efficiency, reduced management costs, and a net profit increase of $1525.86 per hectare.

Fenton cellulose nanofibrils (F-CNF) were prepared by Fenton oxidation with the followed homogenization and then F-CNF /PVA composite films with the F-CNF additives from 1% to 20% were prepared by solution casting method. Scanning electron microscopy (SEM), confocal laser scanning microscope (CLSM), Fourier transform infrared spectroscopy (FTIR), universal tensile testing machine, swelling property detection, thermogravimetric analysis and soil burial degradation rate test were used to characterize the microstructure, chemical structure, mechanical properties, hygroscopicity, thermal stability and biodegradability of the composites. The results showed that a large number of hydrogen bonds were formed between F-CNF and PVA molecules and an acetal reaction occurred. F-CNF can be uniformly dispersed in PVA matrix, and both have good interfacial compatibility. After the addition of F-CNF, the tensile strength and elastic modulus of the composite films were significantly improved, the water absorption of the composite material was reduced, and its thermal stability was improved. When the amount of F-CNF was 15%, the tensile strength and Young's modulus of the composite films were 65.27 MPa and 1460.32 MPa, respectively, which were 217.77% and 830.69% higher than those of pure PVA.

This research investigates the production of biodegradable films using a combination of gum odina (GO) and polyvinyl alcohol (PVA) with varied ratio. The study focuses on the chemical, physical, and mechanical properties of PVA-GO composite films, emphasizing how versatile and biodegradable they may be for a range of packaging applications. Solvent-cast PVA-GO films with different ratios are subjected to a methodical analytical process to determine several parameters like mechanical qualities, thermal stability, biodegradability in soil, contact angle, transparency, water vapor permeability, moisture content, thickness, density, water solubility, microstructure, and FTIR analysis. The outcomes demonstrate that GO improves UV barrier qualities and water vapor permeability. Additionally, the films showed notable biodegradability, acceptable thermal stability, and mechanical qualities. In short, PVA-GO films can provide an eco-friendly packing substitute with adaptable qualities fit for a range of uses. Therefore, this research may further contribute promising information in the field of biodegradable packaging materials in the future. image

Modern agriculture is troubled by white pollution caused by nondegradable polyethylene (PE) mulch film and high transportation costs caused by the large amount of water in liquid mulch film. Aiming at these problems, this study developed a new degradable and water-free powder mulch film (SUPM) with straw powders, urea, and polyvinyl alcohol (PVA) as raw materials. The wind erosion resistance and film-forming properties of SUP powders as SUPM's precursor were investigated as well as the influence of PVA and urea content on the mechanical properties and water resistance of SUPM film. The results showed that PVA in SUPM film was in a gradient distribution conducive to the germination of crop seedlings. Here, PVA colloids were more distributed at the interface between film and air than at the interface between film and soil. The optimized SUPM film exhibited a biodegradation rate of 90.5 % over 100 d. After SUPM film degradation, soil carbon and nitrogen contents were 33.5 and 58.8 % higher, respectively, than in bare soil. In two consecutive planting experiments, pakchoi yields were higher and more stable in the soil with SUPM than in bare soil and soil with PE. Compared to other reported biodegradable mulch films, SUPM demonstrated advantages in ease of use, enhancement of soil carbon and nitrogen content, and stable crop yields. This study provided a new approach for the large-scale utilization of straw waste, mitigating environmental issues caused by traditional PE mulch, and promoting the development of environment-friendly modern agriculture.