Poplar Boards Research Articles

Effect of Two Pomelo Peel Flavonoid Microcapsules on the Performance of Waterborne Coatings on the Surface of Poplar Boards

Two types of microcapsules were added to the coating separately. The specifications of the poplar board were 50 mm × 50 mm × 8 mm. The antibacterial rate of the poplar board surface gradually increased with the increase in the microcapsule content, and the antibacterial activity for Staphylococcus aureus was slightly higher than that against Escherichia coli. Influenced by the change in the wood grain’s color on the poplar board itself, both microcapsules had no significant effect on the chromaticity value and color difference of the poplar board surface, as well as the reflectance of the visible light band. The glossiness decreased with the increase in the microcapsule content, and the gloss loss rate increased with the increase in the microcapsule content. With the increase in the microcapsule content, the hardness of the poplar board surface in both groups increased slightly, and the roughness increased gradually. The adhesion of the poplar board surface coating with melamine-resin-coated pomelo peel flavonoid microcapsules was slightly reduced, and the impact resistance was not significantly affected. Chitosan-coated pomelo peel flavonoid microcapsules had no significant effect on the adhesion of the poplar board surface coating, and the impact resistance increased slightly when the content of microcapsules was higher. Comprehensively, the poplar board coating with 9.0% chitosan-coated pomelo peel flavonoid microcapsules had a better overall performance, with antibacterial activities for Escherichia coli and Staphylococcus aureus of 70.6% and 77.6%, respectively. The color difference was 6.70, the gloss loss rate was 53.9%, the reflectivity was 50.60%, the hardness was H, the adhesion was grade 1, the impact resistance was grade 2, and the roughness was 2.10 μm. The results provide technical references for the application of antibacterial microcapsules of pomelo peel flavonoids on the surface of wood materials.

Mechanical and thermal stability improvement of cellulosic fiber products derived from waste poplar boards under UV irradiation via lignin retention

As a derivative of agriculture crops and forestry cultivated plants, cellulosic fiber product (CFP) is of much industrial interest deemed a promising alternative to wooden composites and plastics owing to the low environmental impact. The high-performance CFP was fabricated via a facile molding and hot-pressing process without using adhesives. The UV aging test was carried out to evaluate the physical and mechanical stability before and after delignification. The tensile strength was increased from 41.3 MPa to 53.7 MPa, and the flexural strength was increased from 72.3 MPa to 85.4 MPa as the lignin was removed from 11.7% to 3.0%. The holocellulose content and crystallinity of fibers were increased, and the fiber dimensions were correspondingly decreased after delignification. However, the delignified specimens exhibited a faster reduction in mechanical strength than that of lignin-rich products (e.g., 0.074 vs 0.041 in the slope rate of fitting curves) throughout the UV irradiation, and the thermal stability was also decreased from 317.2 ℃ to 311.3 ℃ in onset decomposition temperature due to the delignification. Moreover, the lignin-rich CFP was superior to that of typical plastics (e.g., PP and epoxy resin) and wooden composites (e.g., WF/PP) in mechanical and thermal stability under UV irradiation through the comparison. • Cellulosic fiber product (CFP) developed using waste poplar boards via facile process. • Lignin-rich CFP exhibited higher mechanical stability than delignified products. • CFP was superior to that of plastics in properties stability under UV irradiation.

COMPARATIVE STUDY ON PHYSICAL-MECHANICAL PROPERTIES OF PLYWOOD PRODUCED FROM EUCALYPTUS GRANDIS AND POPULUS DELTOIDS VENEERS. SHORT NOTES

Nine-ply plywood panels were produced from Eucalyptus grandisand Populus deltoidsusing urea-formaldehyde (UF) and phenol-formaldehyde (PF) adhesives. The physical and mechanical properties,such as moisture content, density, modulus of rupture (MOR) and modulus of elasticity (MOE) of the eucalyptus and poplar boards, were compared in this study. Samples were tested on both,along and across the grain. Higher values of MOR and MOEwere observed foreucalyptus as compare to poplar. Density of ply board was observed as 500-560kg.m-3in plywood from poplar and 700-720 kg.m-3in plywood from eucalyptus species. These differences were attributed to the variation in properties of veneer wood species. The effect of veneer wood species on some physical and mechanical properties of plywood was found statistically different.

Biodegradable, flame retardant wood-plastic combination via in situ ring-opening polymerization of lactide monomers

A wood-plastic combination (WPC) was created via in situ polymerization of the l-lactide monomer (3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione. Commercial poplar boards (Liriodendron tulipifera) were impregnated with the flame retardant chemical resorcinol bis(diphenyl phosphate)(RDP). These samples were then soaked in a solution of the monomer and deionized water with sulfuric acid 5% wt/wood as a catalyst for polymerization. The wood and solution were placed in a vacuum oven for impregnation and polymerization of the monomers. The wood RDP combination was not flame retardant and had an Izod impact strength that was slightly smaller than neat wood sample. Addition of lactide monomer tripled the Izod impact strength relative to wood, and scanning electron microscope (SEM) images indicated that a polymerized coating had formed which reinforced the porous wood structure. Addition of all three components produced a synergy. The Izod impact strength of the material was nearly 14 times greater and the WPC was flame retardant surpassing the stringent UL-94-V0 requirement.

Mat Compression Measurements During Low-Density Particleboard Manufacturing

This study regards the effect of technological aspects on mat compression during the manufacturing of low-density particleboards made of two low density species - i.e. poplar and pine. Using these materials, three-layer low-density particleboards (500 kg/m3) were prepared. Three series were manufactured: (1) neat pine, (2) poplar-pine (face layer and core layer, respectively) and (3) neat poplar boards. Measurements of real-time variations in mat core temperature, pressure, and mat thickness allowed for the analysis of the mat compaction. Selected mechanical properties (modulus of rupture, modulus of elasticity, and internal bonding) of the manufactured particleboards were determined. Raw material of lower density used for particleboard manufacturing required either prolonged pressing time or more intense heat transfer into the mat core. The highest strength values were obtained for the poplar-pine particleboards.

Sandwich compression of wood: control of creating density gradient on lumber thickness and properties of compressed wood

In order to utilize the plantation poplar wood, white poplar boards were soaked, heated and compressed to improve the mechanical properties in this study. The densities and densified zones were managed inside the board by choosing various parameters of soaking time between 0.5 and 5.5 h, heating time between 20 and 200 s and pressing time between 6 and 60 s. The density gradient was generated with the higher density near surface and the lower density toward the center of board. With this method, the density near the surface can be modified to 0.89 g/cm3 with an increase of about 100 % in comparison with poplar wood without any treatment. The boundary between the high-density layer and the low-density layer was characterized by X-ray scanned images. The modulus of elasticity (MOE) of compressed white poplar wood increased linearly with the compression ratio, and the modulus of rupture (MOR) increased exponentially. At the compression ratio of 47 %, MOE and MOR of compressed poplar wood were 19.77 GPa and 153.94 MPa, respectively. They were 73.2 and 88.9 %, respectively, greater than that of untreated specimens.

Evaluation of the effects of compression combined with heat treatment by nanoindentation (NI) of poplar cell walls

Abstract A combination of compression and heat treatment is a modification method that has great potential for improving the mechanical properties and dimensional stability of wood materials in industrial application. The objective of this project was to track changes in the microstructure, chemical composition, cellulose crystallinity, and mechanical properties of the treated poplar cell wall to investigate the mechanism of modification. Poplar boards were compressed at 100°C and subsequently treated in the hot press at 200°C. The results indicated that the treatment contributed to a reduction in porosity without obvious mechanical compression and damage to the cell wall. Hemicellulose degraded, however, and the relative lignin content and cellulose crystallinity increased during the process. The observed increase in relative lignin content and crystallinity may contribute to the improvement of mechanical properties. The longitudinal elastic modulus and hardness of poplar cell walls increased significantly from 12.5 and 0.39 GPa for the control to a maximum of 15.7 and 0.51 GPa for compressed wood with HT, respectively.

Dimensional Stability of Poplar Wood after Densification Combined with Heat Treatment

Hybrid poplar boards were subjected to thermo-mechanical densification combined with heat treatment. Hydroscopicity and hygroscopicity of the treated samples were measured. The results showed that dimensional stability of the samples was influenced by compression set significantly. The higher the compression set, the greater the swelling of the samples. On the contrary, the influence of densification temperature and duration was not significant. Thermal modification significantly reduced hydroscopicity and hygroscopicity of the samples. Both higher treatment temperature and longer holding time resulted in better dimensional stability.

Temperature distribution in lumber during impingement drying

Techniques are described for measuring the surface temperature of drying lumber with a radiation thermometer and for measuring interior temperatures at various depths with 30-gauge (0.25 mm) thermocouples. Experimental results with 52 mm thick yellow poplar boards dried above 100°C with impinging jets of hot air over a range of temperatures are presented showing surface and interior temperatures and moisture content as functions of drying time. Surface temperatures rose rapidly to within 10 to 30° of dry-bulb temperature, and interior temperature at the center of the boards remained near 100°C until the boards dropped below 10 percent moisture content.