The impacts analysis of moisture content on mechanical properties of wormwood stem

The disposable chopsticks caused a large amount resources waste of bamboo and wood. Thus, it has a significant resources and environmental benefits using wormwood stem as raw materials to make disposable chopsticks. In this paper, the radial compression and bending performances of wormwood stem were tested with different moisture content, which provide a reference for reasonably design the grinding device of wormwood stem and the feasibility of wormwood stem instead of bamboo chopsticks. The test results show that: the mechanical properties decrease with the increase of moisture content. In the actual grinding process, the moisture content of wormwood stem is controlled about 20%, it can withstand the radial force of 600N and the bending force of 41N, which meet the load requirements of the grinding processing and use. This study provides a theoretical basis for reasonably design grinding device of wormwood stem, producing and storing high quality herbal chopsticks.

Short note. Physical and mechanical properties of Paulownia tomentosa wood planted in Hungaria

The Paulownia tree (or to its well-known name Chinese empress tree; Paulownia tomentosa) is classified among the most variable wood species of the world concerning usability. Its cultivation in Hungary in form of research plantations has just started in the last decade, first of all for the investigation of energetic properties. Due to this the information related to the physicalmechanical properties of the wood was still not determined, from which aspect this study is essential. The investigated wood with an air-dry density of 0.3 has shown low bending (42 MPa), compressive (22 MPa), shear (7 MPa), tensile (33 MPa) and impact strength (1.6 values, based on which its wooden material properties can be compared to poplars considering tree species in the region.

Cell wall structure and mechanical properties of Salix psammophila

Salix psammophila can grow rapidly in desert and grassland areas. As an abundant bioresource, it is useful to understand its cell morphology, chemical compositions and mechanical properties. In this study, Anatomical properties of Salix psammophila in different annual rings were measured and compared. Fourier transform infrared spectroscopy and chemical titration were used to estimate cell wall chemical compositions. Moreover, mechanical properties in different annual rings were measured through nanoindentation. Fiber cell lumen diameter, fiber cell wall thickness, vessel cell lumen diameter and vessel cell wall thickness of Salix psammophila were measured to be 7.371, 2.285, 32.541 and 1.926 μm, respectively. Fiber cell lumen diameter, fiber cell wall thickness, vessel cell lumen diameter differs among the annual rings. The cellulose, hemicellulose and lignin contents of Salix psammophila were 44.43, 34.99 and 17.93 %, respectively. Both hemicellulose and lignin contents varied among the annual rings with more hemicellulose but less lignin at the annual ring closer to the pith. The modulus of elasticity (MOE) of fiber cell wall of Salix psammophila decreases from pith
to bark.

Dynamic relationship between mechanical properties and chemical composition distribution of wood cell walls

Wood is a natural composite material with a complex structure. Its mechanical properties are mainly due to the cell walls. In order to investigate the relationship between mechanical properties and chemical composition of wood cell wall. Nanoindentation and Raman imaging were used to characterize the longitudinal mechanical properties and chemical composition distribution of wood fibers of three years old fast-growing poplar (Populus×euramericana cv. ‘74 /76’) during the growing season at different times. The results were showed that the content and distribution of cellulose and lignin are closely related to the mechanical properties of wood fiber cell walls, especially the cellulose for the longitudinal elastic modulus and the lignin for the hardness of cell walls. It was also demonstrated that the longitudinal elastic modulus and hardness of the secondary wall 2 layer (S2) were strongly correlated to the micro fibril angle (MFA) and crystallinity of cellulose during the active phase.

Permeability and mechanical behaviour of microwave pre-treated Norway spruce ripewood

This is a study of the influence of microwave (MW) pre-treatment on the permeability of Norway spruce ripewood (Picea abies L. Karst) as it affects its mechanical properties. Specimens were treated under variable moisture content, MW intensity, and impregnation processes. According to the results, the specimens with an initial moisture content of 45–65% exhibited the highest permeability values compared to reference samples. An insignificant difference was found between MW pre-treatments at 2 and 3 kW. Statistically significant results were found after long-time (24h) vacuum-pressure impregnation (LP). The average retention value following LP was 132 kg.m-3, which is almost three times greater than the MW-treated groups impregnated in a short-time vacuum-pressure process. The average depth of penetration after LP was 2.0 mm and the proportion of the impregnation area following LP was 17.6%. MW pre-treatment had no effect on the impregnability or the mechanical properties of the wood; other MW regimes are open for further examination.

Internal fiberglass mesh reinforced bark-based panels

One-layer bark panels were internally reinforced with two different grid sizes fiberglass mesh sheets (M1 and M2). The thermal conductivity, water absorption, thickness swelling, static bending properties and internal bond strength of these panels were tested. The reinforcement doesn’t affect the thermal conductivity, but the physical and mechanical properties of the panel were improved. The thickness swelling was reduced by 7.43% and 12.93%; the water uptake decreased by 4.93% and 16.32% for the M1 and M2 sheets, respectively. MOR increased from 0.54 MPa to 2.44 and 2.1 MPa, and MOE increased from 0.28 GPa to 0.66 and 0.63 GPa, respectively. The internal bond didn’t change. The findings indicate that it is possible to produce internal reinforced bark panels for insulation materials depending on the characteristics and tensile properties of the reinforcing materials, as well as the adhesion properties and interfacial interaction of the composite materials.

Modification of radiata pine wood with low molecular weight modifying agents and large molecular weight styrene/acrylic acid copolymer dispersion

Our previous study revealed that treatment with aqueous styrene/acrylic acid copolymer (SA) is a cell-lumen filling process, and the treated wood exhibited negative values for cell wall bulking efficiency (BE) and anti-swelling efficiency (ASE). In this study, three low-molecular-weight agents (LMWAs), 1, 3-dimethylol-4, 5-dihydroxyethyleneurea (DM, 10%), glutaraldehyde (GA, 10%), and n-methylol acrylamide (NMA, 10%), were separately combined with SA (5, 10, 15, or 20%) and used to modify radiata pine wood at the levels of cell walls and cell lumens. The combinative treatments caused positive BE and ASE values, indicating restrained wood deformation, likely due to the diffusion and reaction of LMWAs in the wood cell walls. Infrared spectroscopy and dynamic mechanical analysis showed that LMWAs exhibit little reaction with SA, and the SA copolymer retains thermoplasticity in the wood cell lumen. The combinative treatments resulted in considerable improvement in bending modulus, bending strength, and compression strength of wood of 36, 36, and 124%, respectively, but there was little effect on impact strength. These findings confirm that LMWAs can act as cell wall modifying agents to synergistically improve wood properties, especially the dimensionally stability, when used together with SA.

Nanomechanical behavior of wood cell walls observed by different indentation loading prerequisites

The variations of nanomechanical behavior of wood cell walls under different peak loads, loading times, and holding times were studied. Samples were separately loaded to preset peak loads of 100, 150, 200, 250 and 300 μN. Changes in the micromechanical properties were tracked in the longitudinal direction to determine change values of the elastic modulus and hardness. Moreover, the creep behavior was also analyzed under different holding times. It was found that the longer the holding time, the larger the creep ratio of all of the samples, and the creep rate decreased slowly with longer loading times. Finally, when the peak load was larger, the displacement rate and strain rate increased, but the strain rate in each test exhibited a tendency to become constant after 10 s.

Impact of silvicultural measures on the quality of Scots pine wood. Part I. effect of regeneration method

This study deals with the influence of the silvicultural measures on selected mechanical properties of Scots pine (Pinus sylvestris L.) wood in the Czech Republic. Sample trees were selected at two different localities that are characteristic of Scots pine growth, and they represent two different Scots pine regeneration methods, namely the clear-cutting and shelterwood regeneration method. We tested compressive strength and impact bending strength. The density of the wood was also evaluated as a factor influencing strength characteristics. The shelterwood regeneration method shows higher values in most of the investigated characteristics (49.3 MPa for the shelterwood method and 44.6 MPa for the clear-cutting method in the case of compressive strength); however, these differences are not significant for the processing industry. Another positive effect of the shelterwood regeneration method is the even distribution of the properties within the trunk in radial direction in contrast to clear-cutting method.

Effects of manufacture conditions on physical and mechanical properties of rape-polymer boards

The paper presents a method of manufacturing boards composed of lignin-cellulose chips and thermoplastic polymers (waste-based particle polymer composites, WPPC) by means of flat pressing. Rape chips, similar in size to wood chips in traditional particleboards, served as filling material, and polyethylene and polypropylene made up the outer layers. The polymers enriched only the external layers, as this allowed for considerable shortening of pressing time. The resulting boards featured satisfactory properties as compared with control, not polymer covered boards. Our study identified a temperature of 220°C and low moisture content of the polymer-containing layers as favorable for production of this type of boards. We also found out that using a sublayer with higher moisture content not only shortened the pressing time, but also improved the board properties evaluated by a bend test.

Comparison of selected properties of natural aged wood and contemporary timber of Pinus sylvestris L. investigated using standard methods and measuring of transition speed of ultrasounds along the fibre

Scots pine wood (Pinus sylvestris L.) is the most common wood material used in historical buildings in many parts of Central and Eastern Europe. Experiments were conducted natural aged wood (263 – 459 years old), extracted from construction elements of four historical buildings (from seven construction elements), and contemporary wood extracted from 5 construction elements. A strong relationship was observed between density and static bending strength (MOR) of natural aged wood (R2 = 0.5599), and also of contemporary timber (R2 = 0.7863). Antique wood compared to contemporary wood with the same average moisture content and density is characterized by significantly lower modules (static and dynamic), the speed of ultrasonic waves transitions, and bending strength. Differences in these properties increase with increasing wood density.

Mechanical and physical properties of medium density fibreboard with calcite additive

In this study, it is investigated that are calcite filler can be used in the production of medium density fiberboard. Chips have been to the process of cooking for 4-5 minutes in Asplund defibrator with the vapor pressure of 7-7.5 bar, and 180ºC temperature. 1.5% paraffin and 1% ammonium sulphate to be pulverized is added to fibers on the output of defibrillator and blowline line. Calcite fillers are prepared in a separate tank in order to use calcite instead of lignocellulosic fibers in the production of 1 m³ MDF. After that, urea formaldehyde glue is prepared as three different solutions which include the calcite, respectively with 3% (20 kg.m-3), 6% (40 kg.m-3), 9% (60 kg.m-3). The fibers are dried to moisture of 8%-12%. This press applies temperature about 185-190°C and pressure about 32-34 kg.m-2 to the mixture material for 270 seconds during pressing time. MDF panels (2100 x 4900 x 18 mm) were produced in the process. Both mechanical and physical experiments are performed on boards which are produced.

Mechanical properties and set recovery of compressed poplar with glycerin pretreatment

In order to improve the mechanical properties of low-density wood, the densified wood was fabricated. Northeast China fast-growing poplar was firstly immersed in 50% glycerin for 24 h, and then compressed under 150°C to attain 60% compression ratio with different thermal modification time (0.5, 1, and 2 h). The set recovery, modulus of elasticity (MOE), modulus of rupture (MOR) and hardness of compressed wood were tested to assess the influence of thermal modification time and wet/dry cycles on mechanical properties and set recovery of compressed poplar with glycerin pretreatment. It can be found that the thermal modification time of 1 h can be more appropriate, the first wet/dry cycle has a significant effect on mechanical properties and set recovery of compressed wood due to the dilution of glycerin during the soaking.

Effects of polymer additives on some mechanical and physical properties of cement bonded particleboards

The effects of some polymer additives, also called super plasticizers, on selected physical and mechanical properties of cement bonded particle board were investigated. Two different kinds of poly carboxylic ether (PF300, DX40) and a melamine based polymer (300M) were added to the wood cement mixture. The ratios of polymer additives to the wood cement mixture were 1%, 1.2% and 1.4%. Cement bonded particleboards were manufactured with wood/cement (w/w) ratio of 1:3; target density of 1300 kg.m-3, and CaCl2 content of 5%. The cement bonded particleboards were tested for water absorption (2 and 24 hour), thickness swelling (2 and 24 hour), bending stiffness and strength and internal bond strength. Results of the study showed that most of the polymer addition decreased water absorption and thickness swelling of the boards. Replacement of cement with polymers increased internal bond strength and bending stiffness of the boards while bending strength was slightly reduced. Use of small amount of super plasticizers significantly improves most of the board properties.

Effect of pressurized hot water treatment on the mechanical properties, surface color, chemical composition and crystallinity of pine wood

The effect of a pressurized hot water treatment (PHWT) on the mechanical properties, chemical composition, surface color, and cellulose crystalline structure of Pine wood were examined in this study. The effects of PHWT of pine wood at 140, 160, 180, and 200°C for 1, 3 and 5 h were investigated in terms of changes in mechanical properties, chemical composition, surface color and cellulose crystallinity of pine wood by means of a GB/T standard, NREL LAP, Color Difference Meter, and X-ray diffraction (XRD). Both the temperature and treatment time showed significant effects. The results showed that the bending strength and elastic modulus decreased with an increasing temperature and duration. Changes in the chemical components and surface color occurred because of the degradation of the cellulose, hemicelluloses and lignin in the wood during the PHWT. Additionally, the relative degree of relative crystallinity of the samples increased. These findings demonstrated the potential of PHWT for the wood modification.

Properties of medium-density fibreboards bonded with dextrin-based wood adhesive

This study focuses on manufacturing of medium density fibreboard (MDF) panels bonded with dextrin-based wood adhesive and crosslinked in situ with various weight ratios of synthetic (e.g., polymeric-methane diphenyl-diisocyanate, pMDI) or bio-based (e.g., glyoxal) crosslinkers. The physical and mechanical properties of the panels were evaluated and compared with those from panels without crosslinker (control). Modulus of rupture (MOR) and internal bond (IB) strength of the MDF panels were considerably increased by increasing the crosslinkers’ content. While, slight improvements were observed in modulus of elasticity (MOE) of the panels as a function of crosslinker type and content. Addition of crosslinkers clearly reduced the thickness swelling (TS) and water absorption (WA) of the panels, whereas, the panels with pMDI showed superior performances than the control and glyoxal added ones within 4 h and 24 h immersion in water. The results indicate the potential of dextrin as wood panel adhesive along with the use of appropriate crosslinkers.

The effect of thermal modification by hot pressing on the some physical and mechanical properties in rubberwood (Hevea brasiliensis)

Rubberwood (Hevea brasiliensis) was thermal modified by hot pressing in an open system at three different temperatures (170, 185, 200°C) and two different durations (1.5, 3 h), and the effect on the physical and mechanical properties was studied. Results show that the thermal modification increased the oven-dried density and decreased the EMC (equilibrium moisture content) by 7.93% and 37.15%, respectively, and the dimensions stability was improved. Hardness, bending strength, modulus of bending and compressive strength parallel to grain of modified samples basically decreased with increasing temperature and time, but they showed a meaningful increase compared to control samples. However, impacting bending and nail withdrawal resistance decreased after hot pressing and thermal treatment, and the failure of the compensation for the impairment was the rubberwood hot pressed and thermal treated in the presence of air, and the participation of oxygen provoked rapid degradation reactions during the treatment.

Prediction of the mechanical properties of thermally-modified rubber wood on the basic of its surface characteristic

The goal of this research was to investigate the effect of thermal treatment on mechanical properties and surface characteristic of rubberwood (Hevea brasiliensis) and find the mathematical model to predict the mechanical properties used by its surface characteristic. Rubberwood specimens were treated by steaming at five different temperature levels of 170, 185, 200, 215, and 230°C for two different durations of 1.5 and 3 h. Based on the results, the values of bending strength, modulus of elasticity, compression strength and impact bending decreased, and the glossiness and chromatic aberration (∆E) increased with increasing temperature and enlarging duration further. This study revealed that chromaticity parameters b*, ∆E and the gloss of perpendicular to grain (GZT) could evaluate the mechanical properties of thermally-modified wood to achieve the mechanical properties detection without destruction.

Study on the structure and properties of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)/ rubber wood fiber composites modified with titanate coupling agent

In this study, the biodegradable composites were prepared from rubber wood fibers (Hevea brasiliensis) and biopolymer poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) via hot pressing process, using the titanate as the coupling agent. The morphological, chemical structure, mechanical properties and water absorption (WA) of the composites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), mechanical properties and WA analysis. Results showed that a new absorption peak of Ti-O-C was formed due to the addition of titanate, indicating that it was successfully grafted on the surface of wood fibers. In addition, the mechanical properties of the composites first increased and then decreased with the increasing of the titanate content. The obvious improvement of WA of composites was attributed to the inclusion of P34HB by titanate modified wood fiber. Moreover, it was also found that the optimal condition of the titanate coupling agent content was 1 wt%.