钉子植入木材的力学特性试验

通过分析钉子植入木材的过程,确定力学特性试验的方法,依据此方法设计试验装置并进行钉子对木材植入的力学特性试验。通过对试验结果相关数据的处理和分析,得出木材在钉子植入其内的过程中的力学特性,体现为一定的阻尼性和弹性。     

水性木器涂料的研究进展

对水性聚氨酯和水性丙烯酸木器涂料进行了详细介绍。分析了水性木器涂料的研究现状及存在问题,提出了相关的发展趋势和研究方向。     

扬州雕漆、楠木雕“双绝”赵如柏

本文主要介绍了赵如柏大师的学艺经历,和他在传统工艺美术雕漆技艺以及楠木雕技艺方面所取得的成就。     

Study on the two-way corrugated aluminum honeycomb as a filler material in impact limiters for spent fuel transport casks

Impact limiters installed on nuclear spent fuel transport casks are used to absorb energy and limit overload during transport and accidents. The two-way corrugated aluminum honeycomb, a new kind of filler material, is designed based on the action mechanism of the impact limiter. Quasi-static compression tests are used to compare the properties of the honeycomb and the traditional filler material, paulownia wood. Experimental results indicated that the compressive and energy absorption properties of paulownia wood with axial wood grain and radial wood grain were very different. Also, the moisture content of paulownia wood led to a significant decrease in its properties. The two-way corrugated aluminum honeycomb, as a new porous material, showed better compression and energy absorption properties than paulownia wood in the x, y, and z directions. The peak stress (σ_pe), platform stress (σ_pl), and energy absorption capacity (W_EA) were 2.10 times, 2.07 times, and 1.69 times higher than that of paulownia wood with axial wood grain. The two-way corrugated aluminum honeycomb is a filler material that has essential application value in impact limiters of spent fuel transport casks.     

Rods glued in engineered hardwood products part II: Numerical modelling and capacity prediction

The second part of this series of two papers presents the modelling and strength prediction of Glued-in Rods (GiR) experimentally investigated in Part I. Unlike what has been documented in previous publications, significant effort was put into extensive modelling of all components (adhesive, wood, and rods), in particular regarding stress components other than shear. Based upon the material modelling, stresses inside the GiR were estimated through Finite-Element Analysis (FEA), which indicated that transverse tensile strength are at least as significant as shear stresses in their magnitude. Both results mitigate previous research findings that focused on shear-dominated failure mechanisms and neglected transverse tensile strength. Combining the material characterisation with FEA, and reformulating strength in probabilistic terms, then allowed to perform predictions of joint capacities for all 60 experimentally investigated GiR-configurations. The comparison between predicted and experimental values showed a good agreement wit relative difference amounting to –3% for beech GLT, –2% for oak GLT, and +1%, respectively. Unlike Fracture Mechanics and Cohesive Zone Modelling, necessary parameters were solely obtained independently from the GiR itself, and no single parameter had to be back-fitted on the experimental results of the GiR. Results clearly showed that transverse tensile strength of the wood is at least as important as shear strength for joint capacity of GiR, and that longitudinal strength plays a minor role.     

Accurate evaluation of hydrogen crossover in water electrolysis systems for wetted membranes

In fuel cell and electrolysis systems, hydrogen crossover is a phenomenon where hydrogen molecules (H₂) permeate through a membrane, lowering the overall process efficiency and generating a potential safety risk. Many works have been reported to mitigate this undesired phenomenon, but it is yet difficult to accurately measure the rate of hydrogen crossover, particularly when the membrane is fully wetted in water. In this work, we investigated the pressure decay method as a simple, convenient, and low-cost method to characterize hydrogen crossover through wetted membranes for water electrolysis systems. Three different ion exchange membranes were analyzed: Nafion 212, Nafion 115, and in-house sulfonated poly(arylene ether sulfone). We rigorously confirmed our method and data by comparing it to the ANSI dataset with the current state-of-the-art equations of state (EOS) to account for the nonideality of high pressure hydrogen systems. The error from the gas non-ideality was less than 0.03%. As expected, the rate of hydrogen crossover showed high dependency on the temperature; more importantly, hydrogen crossover increased significantly when the membrane was fully soaked in water. For dry membranes, the proposed pressure decay method corroborated well with the literature data measured using other known methods. Moreover, for wetted membranes, the obtained data showed high similarity compared to the GC method which is currently the most reliable method in the literature. We attempted to predict the hydrogen permeability of wetted membranes using the solution diffusion model. The model based on the given thermodynamic parameters overestimated the hydrogen permeability, which can be used to estimate the ion channel tortuosity.     

Improvement of storage stability of UF resins by adding caprolactam

During storage, the structure of urea-formaldehyde (UF) resins suffers modifications due to reactions between monomers, oligomers, polymer and free formaldehyde, leading to increase in viscosity and decrease in pH. Eventually, viscosity reaches a value that renders the resin unusable, and it must be disposed off. This aging process is accelerated if storage temperature increases.The aim of this work is to obtain UF resins with long storage stability, even when exposed to relatively high temperatures, such as 40 °C. The main strategy adopted was the addition of a chain growth blocker, caprolactam. This monofunctional compound reacts with end groups, blocking them and therefore reducing the polymer's reactivity. In addition, a weak base was added to adjust the pH value, instead of the traditional strong base, sodium hydroxide, therefore hindering the Cannizzaro reaction.The storage stability of UF resins with formaldehyde to urea molar ratio of 1.6–2.0 was monitored by pH and viscosity measurements. Caprolactam was added in different amounts and at different reaction stages. It was found that 10% addition at the beginning of condensation led to the best results, giving a much higher storage stability at 40 °C (2 months when compared to 4 days for a commercial UF resin with low F/U molar ratio). As expected, the resin reactivity decreased with caprolactam addition, demanding for longer pressing times for wood-based panel manufacture. These verified the internal bond strength specification for EN 312 - P2 standard class. Formaldehyde content in the panels was above the E1 class limit when fresh or one month old modified resins were used, implying addition of formaldehyde scavengers. The resin stored for 2 months allowed producing panels within E1 limit. These preliminary results demonstrate the concept that addition of an end-group blocker during UF synthesis is an effective strategy for improving storage stability, encouraging future work on alternative compounds and synthesis conditions optimization.     

In-depth material characterization of polyhydroxybutyrate from a forest biorefinery

Large-scale replacement of petroplastics with compostable plastics, like polyhydroxybutyrates (PHB) will contribute to elimination plastic pollution, decrease greenhouse gas emissions, and valorize local biomass resources. Lignocellulose hydrolysates have emerged as potentially sustainable carbon sources for PHB production. For industrial processing, it is necessary to know the polymer properties. Yet, most studies on PHB samples from lignocellulose report few material properties. PHB samples produced from a pilot scale hardwood holocellulose hydrolysate conversion process were characterized and compared with PHB from a sugar hydrolysate and a commercial PHB powder. PHB from hardwood holocellulose hydrolysate was found to be comparable with commercial PHB in all properties. Differential scanning calorimetry and thermal gravimetric analysis showed that all samples had similar thermal behavior, where the melting temperature was 176°C and the decomposition temperature was 293°C. From the melting enthalpy, all samples showed 63% crystallinity. Dynamic mechanical analysis showed a glass transition temperature at 5°C and a crystallization temperature of 57°C. Fourier transform infrared spectroscopy and nuclear magnetic resonance confirmed that the samples were homopolymers comprised of hydroxybutyrate units. The difference among the samples was the number average molecular mass, being lower for wood hydrolysate (246.4 kDa) than sugar hydrolysate (670.3 kDa).     

Lignin and lignin derivatives as components in biobased hot melt adhesives

Hot melt adhesives (HMAs) are formulated for the first time with different lignins as major components, and the developed HMA formulations were tested for gluing paperboard. The best formulations showed equal or even better bond strength compared to a commercial HMA reference. A maximum bond strength of 16.1 N was achieved with a formulation of oxidized cellulose acetate, organosolv lignin, and triethyl citrate, whereas the bond strength of the commercial HMA reference was 10.5 N. The performance was adjusted via the selection of lignin, the formulation, and chemical modification. Lignin modification was not necessary but provided further possibilities for adjusting the properties for different products (reversible vs irreversible adhesive seams) and also for producing plasticizer-free formulations. Modification with tall oil fatty acids enabled the formulation of fully biobased HMAs without any external plasticizer and provided a bond strength as high as high as 8.9 N. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47983.     

RDM脉冲中子饱和度测井仪器应用研究

RDM (Reservoir Data Miner)是最新研制的针对低孔低渗地层的脉冲中子饱和度测井仪。实际测井中套后自然伽马由于受水淹影响发生变形,与裸眼井自然伽马校深困难,提出了替代套后自然伽马的校深索引曲线。通过对套后自然伽马曲线归一化分析,提出了一种水淹层指示方法。