Agricultural crop-based lignin was utilized to modify phenol-formaldehyde (PF) resin to prepare fast curing biobased phenolic resins by copolymerization.

No abstract

Abstract:Demethylation technique has been used to enhance lignin reactivity for preparation of phenolic resins. However, the demethylation efficiency and the demethylated lignin (DL) reactivity were still unsatisfactory. To improve the demethylation efficiency, alkali lignin was demethylated under different mild conditions using sodium sulfite as a catalyst. Lignin and DL were characterized by 1 H-NMR (nuclear magnetic resonance) and Fourier transform infrared (FT-IR) spectroscopy to determine the demethylation mechanism. With the demethylation of lignin, the methoxyl group content decreased from 1.93 m mol/g to 1.09 m mol/g, and the phenolic hydroxyl group content increased from 0.56 m mol/g to 0.82 m mol/g. These results revealed that methoxyl groups were attacked by SO 3 2− , and some methoxyl groups were converted to phenolic hydroxyl groups by a nucleophilic substitution reaction, generating DL with high reactivity. The chemical properties of lignin-based phenolic resins were studied by 13 C-NMR and FT-IR spectroscopy, and their physical properties were also investigated. The results indicated that lignin-based phenolic resins exhibited faster curing rate and shorter gel time. In addition, the bonding strength increased from 0.92 MPa to 1.07 MPa, and the formaldehyde emission decreased from 0.58 mg/L to 0.22 mg/L after lignin demethylated at the optimum condition.

No abstract

No abstract

No abstract

No abstract

The porous Ti6Al4V alloy has emerged to solve the biomechanical mismatch between implant and bone as its tunable mechanical properties. Cell-surface interaction is related to numerous factorsthe surface’s chemical composition, morphological structure, and external effect. The microarc oxidation (MAO) method was employed in this study to improve the surface properties of scaffolds produced by Electron Beam Melting (EBM), and low-intensity pulse ultrasound (LIPUS) provides physical stimulation for cells in vitro. Although MAO-treated and untreated scaffolds shared the same three-dimensional (3D) structures, the former recreated a more affinity surface than the latter in the 3D room, which could stimulate cell adhesion, proliferation, and differentiation. Therefore, MG63 cells were represented with a stereoscopic cytoskeleton structure on the MAO-treated scaffold as numerous cellular filopodia/lamellipodia with rich extracellular matrix secretion, while flat and sheetlike cells were observed on the untreated scaffold. The expression of ALP, OCN, BMP2, Bmpr1a, and Runx2 were up-regulated by the MAO-treated scaffold; in addition, LIPUS stimulation effectively promoted cell proliferation and osteogenesis differentiation. In the future, the EBM–MAO strategy can be applied to prepare 3D hierarchical macro-/microstructure titanium implants for bone grafts, and LIPUS stimulation can be used as a therapeutic method simultaneously.