An eco-friendly wood adhesive based on waterborne polyurethane grafted with gelatin derived from chromium shavings waste

Depollution of Polymeric Leather Waste by Applying the Most Current Methods of Chromium Extraction

The leather industry is one of the most polluting industries in the world due to the large amounts of waste following raw hide processing but also due to the high content of chemical substances present in leather waste. The main problem with chromium-tanned leather solid waste is related to the storage, due to the ability of chromium to leach into soil or water, and also owing to the high ability of trivalent chromium to oxidize to its toxic form, hexavalent chromium. The purpose of this article is to present the most current methods of chromium extraction from solid tanned leather waste in order to obtain non-polluting leather, which can constitute secondary raw material in new industrial processes. The extraction methods identified in the present study are based on acid/basic/enzymatic hydrolysis and substitution with the help of organic chelators (organic acids and organic acid salts). In addition, this study includes a comparative analysis of the advantages and disadvantages of each identified extraction method. At the same time, this study also presents alternative chromium extraction methods based on the combination of conventional extraction methods and ultrasound-assisted extraction.

Preparation of a high-strength, hydrophobic performance starch-based adhesive with oxidative cross-linking via Fenton's reagent

Starch is a highly attractive carbohydrate in the production for the preparation of adhesives in recent years, due to its widespread availability, renewability, and abundance of reactive hydroxyl groups. However, the mechanical properties, hydrophobicity, self-adhesion, and particularly high energy efficiency are generally unsatisfactory for current starch-based adhesives. On this premise, starch was oxidized using Fenton's reagent in a ""one-pot cooking" process. The prepared oxidized starch was chain expanded by polyvinyl alcohol (PVA) and then cross-linked with a 10 % isocyanate (PM-200) to fabricate a starch-based adhesive (SFA) with a network crosslinked structure. SF12A35%/2.5-55 adhesive shows significantly higher wet shear strength (1.18 MPa), a remarkable 94 % increase compared to SF0A35%/2.5-55. The adhesive film also demonstrates both hydrophobicity (99° contact angle) and exceptional energy efficiency, with a DSC test revealing a notable 10 % elevation in energy efficiency. In addition, the crosslinked structure increases its molecular weight, thereby increasing its self-adhesion (Fig. S1). This study opens up new possibilities for the design and manufacture of multifunctional starch-based adhesives.

Preparation and Properties of a Novel Cross-Linked Network Waterborne Polyurethane for Wood Lacquer

Waterborne polyurethane (WPU) is a waterborne coating with excellent physicochemical properties. Its deficiencies of water resistance, chemical resistance, staining, and hardness have limited the wide application of polyurethane in the wood lacquer market. In this study, polycarbonate diols (PCDL) were used as soft segments and WPCU was modified by cross-linking using Trimethylolpropane (TMP) to prepare polycarbonate type WPU (WPCU) with cross-linked network structure. The new wood lacquer was prepared by adding various additives and tested by applying it on wood board. The successful synthesis of WPCU was determined by FTIR testing, and the cross-linking degree of WPCU was probed by low-field NMR. The viscosity of the cross-linked WPCU emulsion showed a decreasing trend compared to the uncross-linked WPCU emulsion, and WPCU-2 had the smallest particle size. Compared with the uncrosslinked WPCU film, the crosslinked WPCU film had lower water absorption (2.2%), higher water contact angle (72.7°), excellent tensile strength (44.02 MPa), higher thermomechanical, and better water and alcohol resistance. The effect of crosslinker content on the microphase separation of WPCU chain segments on the surface roughness of the film was investigated by SEM. The wood paint prepared by WPCU emulsion has good dry heat resistance, chemical resistance, and adhesion, and the hardness of the wood paint when the TMP content is 3% reaches H. It also has good resistance to sticky stains, which can be used to develop new wood lacquer.