Understanding the bonding mechanism of the interfacial region between bamboo and adhesives is essential for accelerating the development of improved adhesives for advanced bamboo-based materials. In this study, Br-labelled phenol-formaldehyde (PF) resins with four different molecular weights (MWs) were used to make bamboo–adhesive interfaces for tracing the adhesives in bamboo. Ultra-depth-of-field microscopy and scanning electron microscopy in conjunction with energy dispersion spectrometry were used to access the distribution and penetration of resin in the bamboo polymer. Fourier transform infrared images and solid-state cross-polarization/magic angle spinning nuclear magnetic resonance spectra were used to access the molecular-scale interactions between PF resins and bamboo cell walls. The results showed that the PF resins with high MW infiltrated into the lumina of damaged bamboo cells near the bondline to form glue nails, while those with low MW penetrated into the bamboo cell wall to form nanomechanical interlocking. Chemical bonds and secondary forces such as polar forces and hydrogen bonds were generated between bamboo and PF resin. Finally, the twice-adhesive dispensing method combining low-MW resins with high-MW resins was used to improve the bonding strength of the interface.
12 September 2022 in Journal of Colloid and Interface Science
Our aim was to compare the utility and accuracy of the Chinese Version of Montreal Cognitive Assessment Basic (MoCA-BC) and the Montreal Cognitive Assessment-Beijing Version (MoCA-BJ) in the identification of mild cognitive impairment (MCI) under different education levels. A sample of individuals with MCI (n = 295), Alzheimer's disease (AD; n = 254), and normal controls (NC; n = 259) at 2 Memory Clinics and communities was administered the MoCA-BC, MoCA-BJ, Mini-Mental State Examination (MMSE), and other neuropsychological tests. The discriminant validity of the MoCA-BC and MoCA-BJ as diagnostic instruments was ascertained. The overall discriminant validity for detection of MCI from NC (receiver operating characteristic area under the curve [95% confidence interval]) was that the MoCA-BC (0.95 [0.93, 0.97]) had better sensitivity and accuracy than MoCA-BJ (0.87 [0.84, 0.90]). In addition, we provide an easy to use table that enables the conversion of MoCA-BC to the MoCA-BJ scores or to MMSE scores. The MoCA-BC and MoCA-BJ provided good diagnostic accuracy when compared to MMSE. The MoCA-BC, which was proved to be an appropriate tool when screening for MCI among elderly subjects, can now be compared directly with the MoCA-BJ.
The bamboo fiber-based composite (BFBC) has high-performce in terms of mechanical properties and dimensional stability. In this study, BFBCs were prepared with different hot-pressing temperatures (150 °C, 160 °C, 170 °C, 180 °C, 190 °C, and 200 °C) and designed with different densities (1.05 g/cm3, 1.10 g/cm3, 1.15 g/cm3 and 1.20 g/cm3), and their selected properties were evaluated. Temperature affected BFBC performance, which, with a general increase in temperature, showed a decrement in mechanical properties and an improvement in dimensional stability. Holocellulose content significantly decreased, and the color of BFBC became darker with the increasing of the press temperature. As the density of BFBC increased, the modulus of elasticity (MOE) significantly increased from 23.09 GPa to 27.01 GPa with the increase in temperature. The thickness swelling ratio (TSR), width swelling ratio (WSR) and water absorption ratio (WAR) declined by more than 30% with the increase in density. Overall, the results of this study provide a theoretical basis and a source of technical support to promote the design, application, and popularization of BFBC in different fields.
The process of bamboo-oriented strand lumber (BOSL) represents one of the best opportunities for automation, property control and consistency, and high utilization of material from abundant, fast-growing, and sustainable bamboo. In this study, BOSLs were prepared, with reference to the preparation process of bamboo scrimber, by compressing and densifying constituent units under the action of moisture-heat-force and resin polymerization, and then the effects of density variation on their physical and mechanical properties were investigated. The results revealed that the modulus of rupture, modulus of elasticity, compressive strength and shear strength of BOSL with density of 0.78–1.3 g/cm3 ranged from 124.42 to 163.2 MPa, 15,455 to 21,849 MPa, 65.02 to 111.63 MPa, and 9.88 to 18.35 MPa, respectively. The preparation of BOSL with bamboo as raw material could retain the good mechanical properties of natural bamboo, and produce bamboo-based structural products with different properties by controlling the density. The high strength of BOSL with high density was primarily due to the increased volume fraction of elementary fibers, the reduced porosity, and the enhanced gluing interface. The performance of BOSL can be comparable to, or surpass that of, wood or bamboo products. This study provided necessary basic research for the engineering design and application of BOSL.