Preparation and Properties Study of Wood-Based Cushioning Materials.

Traditional cushioning package materials, such as Expended Polystyrene (EPS) and Expanded Polyethylene (EPE), were made with petroleum-based plastics, which are harmful to the environment. It is crucial to develop renewable bio-based cushioning materials that can replace the aforementioned foams due to the rising energy demands of human society and the depletion of fossil fuels. Herein, we report an effective strategy for creating anisotropic elastic wood with special spring-like lamellar structures. Selective removal of lignin and hemicellulose by simple chemical treatment and thermal treatment of the samples after freeze-drying results in an elastic material with good mechanical properties. The resulting elastic wood has a reversible compression rate of 60% and a high elastic recovery (99% height retention after 100 cycles at 60% strain). Drop tests revealed that the elastic wood has excellent cushioning properties. In addition, the chemical and thermal treatments also enlarge the pores in the material, which is favorable for subsequent functionalization. By loading the elastic wood with a muti-walled carbon nanotube (MWCNT), electromagnetic shielding properties are achieved, while the mechanical properties of elastic wood remain unchanged. Electromagnetic shielding materials can effectively suppress various electromagnetic waves propagating through space and the resulting electromagnetic interference and electromagnetic radiation, improve the electromagnetic compatibility of electronic systems and electronic equipment, and ensure the safety of information.

Review on Wood Deformation and Cracking during Moisture Loss.

Wood, being a natural hygroscopic material, the interaction between wood and moisture plays a crucial role in wood processing and utilization. Moisture affects the physical and mechanical properties of wood, and is also one of the main external factors that cause wood deformation and cracking. Drying shrinkage is a common phenomenon during the processing and utilization of wood induced by moisture loss. Drying stress is the main cause of wood deformation and cracking. The shrinkage differential between tangential and radial direction and moisture content gradient of wood are two reasons induced the generation of drying stresses. In this review, the existing states of moisture in wood and the interaction between water molecules and wood components were systematically summarized. The current research progress and deficiencies in three aspects including the factors resulted in deformation and cracking in wood caused by moisture loss, the correlation between wood mechanical properties and moisture, as well as the development of deformation and cracking in wood under moisture loss were discussed. This review aims to facilitate further research on the deformation and cracking of wood under moisture loss by providing valuable insights and assistance, ultimately reducing the occurrence of wood deformation and cracking. And thus, it will enhance the overall utilization of wood resources, making wood better serve human life.

Determination of Moisture Content and Shrinkage Strain during Wood Water Loss with Electrochemical Method.

Moisture content and shrinkage strain are essential parameters during the wood drying process. The accurate detection of these parameters has very important significance for controlling the drying process and minimizing drying defects. The presented study describes an electrochemical method to determine wood moisture content and shrinkage strain during drying, and the accuracy of this method is also evaluated. According to the results, the electrical resistance of the samples increased with the decrease in wood moisture content. As the moisture content changed from 42% to 12%, the resistance increased from 1.0 × 107 Ω to 1.2 × 108 Ω. A polynomial fitting curve was fitted with a determination coefficient of 0.937 to describe the relationship between moisture content and electrical resistance. In addition, both the shrinkage strain and resistance change rate increased with the decrease in wood moisture content, especially for the moisture content range of 23% to 8%, where the shrinkage strain and resistance change rate increased by 4% and 30%, respectively. The shrinkage strain increased exponentially with the increase in the resistance change rate; thereby, an exponential regression equation was proposed with a determination coefficient of 0.985, expressing the correlation between the two. This demonstrates the feasibility of the electrochemical method for measuring wood moisture content and shrinkage strain.

Manufacturing and Characterization of Modified Wood with In Situ Polymerization and Cross-Linking of Water-Soluble Monomers on Wood Cell Walls.

Fast-growing plantation wood has poor dimensional stability and easily cracks, which limits its application. As wood modification can improve the dimensional stability, strength, and other properties of wood, it has been extensively used. In this study, 2-Hydroxyethyl methacrylate (HEMA) and glyoxal were applied to treat poplar wood (Populus euramevicana cv.I-214) by using vacuum pressure impregnation to improve its dimensional stability. The weight percentage gain (WPG), anti-swelling efficiency (ASE), water absorption rate (WAR), leachability (L), and other properties of modified wood were examined. Results showed that the modifier was diffused into the cell walls and intercellular space and reacted with the wood cell wall after heating to form a stable reticular structure polymer which effectively decreased the hydroxyl content in the wood and blocked the water movement channel; thus, further improving the physical performance of wood. These results were confirmed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR). When the ratio of the modifier was 80:20, the concentration of the modifier was 40%, and the curing temperature was 120 °C, the modified poplar had the best performance, which showed a low WAR (at its lowest 58.39%), a low L (at its lowest 10.44%), and a high ASE (of up to 77.94%).

Moisture-Related Shrinkage Behavior of Wood at Macroscale and Cellular Level.

Due to wood moisture sensitivity, shrinkage cracks tend to present wooden structures. These failures are caused by moisture-related shrinkage behavior. In order to avoid it, it is necessary to have a better understanding of shrinkage behavior. In this respect, studying the dimension changes in wood at different scales is of utmost significance for a better understanding of the shrinkage properties. Herein, the shrinkage behavior of Masson pines (Pinus massoniana) wood was investigated at macroscopic and cellular levels during moisture loss via digital image correlation using VIC-3D and digital microscopic systems, respectively. According to the full-field strain maps, shrinkage strain near the external face was higher than that at the internal face, which increased susceptibility to cracking at the external face of lumber. Additionally, the anisotropic shrinkage of wood was explored. The shrinkage ratio at the end of drying was about 5.5% in the tangential (T) direction and 3.5% in the radial (R) direction. However, at a cellular level, the shrinkage ratios in the T and R directions of earlywood tracheids were 7.13% and 2.46%, whereas the corresponding values for latewood tracheid were 9.27% and 5.52%, respectively. Furthermore, the maximum T/R shrinkage ratio at the macroscopic level (1.7) was found to be similar to the value of latewood tracheid (1.72). The earlywood showed high anisotropic, its T/R shrinkage ratio was 2.75. The macroscopic shrinkage was the result of the interaction of the tracheids of earlywood and latewood and was mainly dominated by latewood tracheids.

[Time-effect reaction observation of micro-invasion embedded poly glycolide-co-lactide suture in Sanyinjiao (SP6) in healthy subjects by using magnetic resonance].

OBJECTIVE: To observe the time-effect of stimulation of the embedded poly glycolide-co-lactide (PGLA) suture in Sanyinjiao (SP6) area in normal human body, so as to provide an experimental evidence for clinical application of micro-invasion suture-embedding at an appropriate interval. METHODS: A total of 8 healthy volunteer students (3 boys and 5 girls, ranging in age from 24 to 27 years) were recruited in the present study. A piece of sterilized PGLA suture was implanted into the left SP6 using minimally invasive surgery after strict local skin disinfection. The fat-suppression T2 weighted magnetic resonance images (MRI, displaying local lesion after eliminating interference of fat tissue signals), and T2 mapping 8-echo train images were acquired before and 8 h, 3, 7, 10 and 14 days after PGLA suture embedment by using a MR imaging system. After transformation of the T2-mapping 8-echo train images into T2-mapping images by using a relevant software, the T2 values (meaning the relaxation time of the local muscle) of the left SP6 were measured, followed by analysis of the signal intensity of T2 weighted fat-suppression images and T2 values at different time-points. RESULTS: Before the suture embedding, no abnormal signals were found in the signal intensity of T2 weighted fat-suppression images. After PGLA suture embedment, the local signal intensity of T2WI fat-suppression images was relatively increased at the 8th h, and on day 3, 7, 10 and 14 relevant to pre-embedment, but gradually atte-nuated on day 10 and 14. The T2 values were significantly increased at the 5 time-points of post-embedment (all P<0.01), but without significant differences among the 8thh, the 3rd and 7thd (P>0.05), and being markedly lowered on day 14 relevant to day 7 (P<0.01) in spite of being still markedly higher than that of pre-embedding (P<0.01). CONCLUSION: The signal intensity of T2 weighted fat-suppression images and T2 values acquired from PGLA-suture-embedded SP6 acupoint area in healthy subjects may keep at least for 2 weeks, suggesting that the stimulating reaction of suture-embedment persists more than 14 days. Hence, when a micro-invasion embedding with PGLA suture performed, the interval of two weeks would be appropriate.