To address the depletion of non-renewable resources and align with the principles of green development, researchers increasingly turned to natural plant extracts to synthesise bio-based waterborne polyurethanes (BWPU) as a sustainable alternative to conventional petroleum-derived BWPUs. Although BWPU demonstrated low emissions and non-toxic characteristics, they still exhibited limitations in heat resistance and relatively reduced biodegradability. Thus, to enhance the overall performance of BWPU, sorbitan monooleate (SP) and quercetin (QC) were incorporated into the formulation of hybrid waterborne polyurethane (CWPU). As natural bio-based hybrid materials, QC and SP facilitated the formation of cross-linking networks and hydrogen bonds, enhancing intermolecular interactions and conformational stability in self-cross-linking CWPU. The research concentrated on investigating the chemical structure, mechanical properties, thermal characteristics, and biodegradability of CWPU. The results demonstrated that the introduction of QC constructed a dense cross-linking network, leading to an increase in elongation at the break of CWPU from 460 % to 864 %. Under the condition of 5 % weight loss (T5%), the thermal stability of CWPU was significantly enhanced, with the decomposition temperature increasing from 200 to 243 degrees C. In addition, after degradation in soil and in a 0.6 % lipase PBS buffer for 28 days, the weight of CWPU decreased to 53 % and 48 %, respectively. CWPU can optimise the utilisation of BWPU in biomedical and packaging applications, thereby contributing to innovations in environmentally friendly materials.

Loess exhibits poor engineering properties, such as low strength and poor water stability. Conventional materials used for improving loess, such as cement and lime, result in environmental pollution issues throughout their production and application processes. To assess the efficacy of bio-based materials, including calcium alginate (CA), xanthan gum (XA), cotton fibers (CO) and flax fibers (FA) in the treatment of loess, the improved soil's strength, disintegration, and water resistance were examined. Subsequently, an optimal amendment approach was determined, and dry -wet cycle tests and microscopic observation were performed. The results show that 1.0 % calcium alginate can effectively enhance the strength of loess, significantly improving its resistance to disintegration with almost no observable disintegration; permeability is significantly reduced, and water repellency is enhanced. 2.0 % xanthan can improve the strength and disintegration resistance of loess, but the improvement in strength is lower than that of calcium alginate. Additionally, the improved soil with XA experiences a flocculent disintegration in static water, which cannot maintain the soil structure. Cotton fibers and flax fibers can enhance both compressive and tensile strength of the soil. The content of 0.45 % flax fibers is considered the optimal choice as it has no effect on water stability. Combining the above results, the combination of 1.0 % CA and 0.45 % FA has been selected to improve the loess, which effectively improves the comprehensive mechanical properties and water stability of the composite improved soil. The decrease in strength and mass loss rate are significantly reduced after dry -wet cycle tests. Microscopic tests show that calcium alginate connects soil particles by Ca2+ ionic bridges, which allows the cementing materials to fill the loess pores and exert the role of agglomeration and coagulation to enhance the integrity of the loess. This study shows that the bio-based material with calcium alginate as the main body can effectively improve the mechanical strength and water stability of the loess.