Biološka trajnost i tehnička svojstva toplinski modificirane topolovine

Abstract The aim of this study was to evaluate the effect of brown rot fungus Coniophora puteana activity on physical and mechanical properties as well as biological resistance of heat-treated poplar wood. Two poplar wood species (Populus deltoids and Populus nigra) were heat-treated by thermo-wood (Thermo-D) method. Control and heat-treated specimens were exposed to brown rot fungus C. puteana for 16 weeks. Physical and mechanical characteristics of specimens including density, compression strength parallel to the grain and impact strength were evaluated before and after exposure to fungus. Mass loss of specimens caused by fungal activity (MLF) was also calculated. In addition, the effect of thermal modification on laccase production by C. puteana was assayed. The highest mass loss due to fungal deterioration was observed in control specimens, coinciding with the highest substrate-enzyme interactions and constant decrease in detectable laccase levels. According to the results, thermal modification can be used effectively to protect poplar wood against brown rot fungus attack.Cilj ovog istraživanja bio je procijeniti utjecaj gljive smeđe truleži Coniophora puteana na fizička i mehanička svojstva te na biološku otpornost toplinski modificirane topolovine. Dvije vrste topolovine (Populus deltoids i Populus nigra) toplinski su modificirane postupkom thermo wood (Thermo D). Kontrolni i toplinski modificirani uzorci bili su izloženi 16 tjedana gljivi smeđe truleži C. puteana. Prije i nakon izlaganja gljivama određena su fizička i mehanička svojstva uzoraka uključujući gustoću, čvrstoću na tlak paralelno s vlakancima i čvrstoću na udarac. Također je izračunan gubitak mase uzoraka kao posljedica aktivnosti gljiva (MLF). Osim toga, ispitan je utjecaj toplinske modifikacije na stvaranje lakaze zbog djelovanja gljive C. puteana. Najveći gubitak mase, tj. najveća razgradnja nastala djelovanjem gljive zabilježena je na kontrolnim uzorcima, a to se podudara s najjačim međusobnim djelovanjem supstrata i enzima te s konstantnim smanjenjem detektirane razine lakaze. Prema dobivenim rezultatima, toplinska se modifikacija može učinkovito iskoristiti za zaštitu topolovine od napada gljiva smeđe truleži

Influence of combined hygro-thermo-mechanical treatment on technical characteristics of poplar wood

Combined hygro-thermo-mechanical technique was adopted and used for densification of poplar wood instead of sole treatment. This technique is combination of two techniques of hygrothermal treatment and densification of wood. For treatment, poplar wood blocks were initially treated hygrothermally at temperatures of 130, 150 and 170°C for holding time of 20, 40 minutes. Afterwards, the densification process was carried out under a hot press (temperature 160°C for 20 minutes). For densification compression set was adjusted for 40 and 60 percent based on the initial thickness (radial direction) of the blocks. The densified and non-densified wood blocks were tested for physical and mechanical properties as density, water absorption, thickness swelling, springback, bending strength, modulus of elasticity as well as shear strength parallel to grain. Results revealed that wood properties were enhanced due to the combined hygro-thermo-mechanical -treatment. According to the results, wood density was increased due to the combined hygro-thermo-mechanical -treatment significantly. The treatment improved the dimensional stability of the densified samples. It was also found that the combined hygro-thermo-mechanical -treatment could significantly improve mechanical properties and also reduce the springback in the densified poplar wood

The influence of fiber chemical treatment on prevention of biologic deterioration of medium density fiberboard (MDF)

Abstract In this research, the effects of acetylation on the prevention of white-rot and brown-rot fungi deterioration in medium density fiberboard (MDF) were investigated. Sample boards were made from acetylated poplar fibers, which were treated at different times (0, 30, 90 and 270 minutes) to obtain different weight percent gains (WPGs of 0, 4.85, 9.1, and 15.8 %). Totally  twelve samples boards at three replication for every treatment were made.. The results were analyzed based on a complete randomized design (CRD) under a factorial experiment. Results revealed that the acetylation decreased the deterioration effect of white-rot and brown-rot fungi. As it was determined, the weight reduction of acetylated boards with the highest WPG (15.8 %) after 16 weeks were measured as 1.605 % and 16.93 % for white and brown-rot fungi, respectively. It was also determined that the weight loss of the control (untreated boards) samples was measured as 39.96 and 49.31% in the same period. The research results showed that the acetylation enhances biologic resistance in  medium density fiberboard

Investigation of determinants of stress in patients requiring endodontics therapy: stress in patients requiring endodontics therapy

Abstract: Objectives: Dental stress is often considered as one of the important factors related to the patient's avoidance of dental visits. Considering the lack of comprehensive studies in this regard in Iran, we decided to design a study to explore the causes of dental stress. Material and Method: The DASS (Depression-Anxiety-Stress Scale) was used for data collection. The first part of the questionnaire was related to demographic characteristics, including age, sex, education level and occupation and dental treatment experience. The second part included 21 questions related to the stress. The relationship between the score of questionnaire and psychological and demographic factors were analyzed. Result: Two hundred and fifty-eight patients completed the questionnaires (129 men,129 women). the highest age frequency was seen in the 21-30-year-old group (n=93). The mean age of the patients was 32 years old. women had higher stress scores (p=0.054), First timers had higher mean score to patients with a positive history of dental visit or endodontics treatment (p=0.03). level of education was no related to the stress score. Stress level had negative correlation with age (p=0.03)  Conclusion: Demographic and psychological factors are related to the stress. It's necessary to know the cause of stress in dentistry to have a better control on patient and better treatment procedure

Study the basic building wooden structures to withstand the effects of weather and destructive biological agents Alborz research center

With full respect for the principles of linking wood and conservation project Eldar pine because having good mechanical properties and availability of a wood structure in the form of pavilions chose alcove to the octagon without internal column with computer software Sketch up of Alborz research center with trees and landscaping of the complex was built. In making these structures all stages of the preparation of the wooden parts of drying are quite principled and dried in the open air during the six months were roof wood structure with the use of Eldar pine just Lambe was made in setting up the ceiling of solar connection on an octagonal timber wood using mortise and tenon mode and auxiliary metal was used. Sliding windows can be made to occupy less space. After completion of the period of three months to review the different pieces in different parts of the structure and measurements of physical densities, shrinkage and swelling and mechanical testing of hardness and impact resistance and protection review different parts of the fungal infection and decay structures was investigated. Since shortly after the beginning of the measure is going to change in the early stages of measuring statistically Darnbvdh but in the last stage of a decrease in density of about 5% and reduce the hardness of about 8% were signs of shrinkage and swelling in various parts of it to be seen

The effect of press temperature and press time on Medium Density Fiberboard (MDF) properties produced from EucalyptusIntertexta fibers

In this investigation, the influence of press temperature and press time on MDF properties made from Eucalyptus wood (Eucalyptus intertexta sp.) have been studied. Variable factors were steaming time (in two levels: 5 and 10 minutes), press temprature (in two levels: 180 and 190 °C ) and press time (in three levels: 3, 3.5 and 4 minutes).    The results of this study indicated that the effect of steaming time on MOR had been significant, the highest MOR were obtained 14.62 Mpa in MDF boards that produced in 5 minutes steaming time. Also the MOR of boards were increased with ascending of press temperature. The results also showed that the effect of press temperature on MOE had been significant and MOE of boards were increased with ascending of press temperature. The results revealed that increasing of steaming time and press time had been negative effect on IB. on the other hand press time  had a significant effect on  thickness swelling as the minimom of thickness swelling had obtained in 3 minutes press time

A Study of Concept to Prepare Totally Biosourced Wood Adhesives from Only Soy Protein and Tannin

This is a study of concept on the initial application for wood adhesives totally biosourced from the covalent reaction between soy protein isolate (SPI) and a commercial flavonoid tannin, namely quebracho tannin. The adhesive is composed exclusively of the two vegetable biomaterials mentioned and thus is totally biosourced and non-toxic, as tannin has been classified as being not at all toxic by the European Commission REACH program. The pre-reaction between the two yielded the best plywood bonding results when limited to a temperature of 40 °C, final cross-linking being achieved during the plywood higher temperature hot pressing procedure, as for any other thermosetting adhesive. Pre-reaction at higher temperatures, namely 60 °C and 80 °C, achieved extensive premature cross-linking that lost any activity to cross-link further when hot pressed for preparing plywood. The reaction was followed by thermomechanical analysis, by matrix assisted laser desorption ionization time of flight (MALDI ToF) mass spectrometry, and by plywood shear strength tested dry, after a 24 h cold water soak and 1 h in boiling water. The adhesive of this approach lends itself to be further reinforced by the multitude of approaches on soy resins already developed by several other research groups

The impact of reeds residue addition on physical and mechanical properties of particleboard made from pomegranate prunings

The impact of reeds residue addition on physical and mechanical properties of particleboard made from pomegranate pruning was investigated. Laboratory particleboard  was made applying one of the three levels of   press time (3, 4 and 5 minutes) and  one of the four levels of reed and pomegranate pruning mixture (1-100% reeds; 2- 75% reeds + 25% pomegranate pruning; 3- 50% reeds + 50% pomegranate pruning and 4- 25% reeds + 75% pomegranate pruning). Boards were made in three replicate and 36 boards were made. Boards were tested using relevant EN standard and results were analyzed based on complete randomized design (CRD) under factorial experiment. Results revealed that increasing of pomegranate pruning in the wood mixture imposed positive effect on MOR, MOE, IB and thickness swelling of the particleboard. The relevant values of MOR, and MOE of the boards produced using 25% reeds + 75% pomegranate pruning  were determined as 16.20 MPa and 2533 MPa respectively. Also thickness swelling after for 2 and 24 hours soaking in water decreased from 17.51 and 33.21% to 9.33 and 16.84% respectively. Internal bond strength (IB) of boards made applying 3 minutes press time (0.17 MPa.) was higher than boards made pressed for either 4 or 5 minutes, which indicates that 3 minutes press time is the appropriate time to approach maximum MOR and minimum thickness swelling after 24 hours soaking in water

Investigation on the Properties of Cement Fiber Board Produced Using Waste Paper

In this study, the reinforcing effect of recycled newsprint paper (RNP) in cement boards has been investigated. The experiment was designed to apply two variable factors, RNP and calcium chloride (CaCl2). Cement-fiber boards with the density of 0.7 kg/m3 were manufactured using fiber/cement ratios of 10:90, 15:85, 20:80 and 25:75 (w/w) and 3% and 5% CaCl2 as accelerator. Minimum four boards (replications) were fabricated for each combination of variables, and the mechanical and physical properties of the boards were evaluated. The statistical analysis showed that the effect of the RNP and CaCl2 contents on modulus of rupture of cement fiber boards were significant at 1% significant level. The results showed that addition of CaCl2 enhanced the mechanical properties of the boards. All properties of the boards were improved as the CaCl2 content was increased from 3% to 5%. The modulus of rupture and modulus of elasticity of the boards decreased with addition of RNP, and the maximum values were obtained at RNP loading of 10%. The results also showed that as the fiber content was increased, significant increase in water absorption and thickness swelling occurred. Increasing RNP fiber content from 10% to 25% reduced both the mechanical and physical properties considerably. The optimum condition was obtained when the RNP and CaCl2 contents were 10% and 5%, respectively

Wood plastics composites: Bond formation mechanism and mechanical properties

Wood fibers are increasingly being used as reinforcement in commercial thermoplastic composites due to their low cost, high specific strength properties and renewable nature. The ultimate goal of our research was to find the fundamental understanding of the mechanical behavior of poplar wood fiber/polypropylene (PP) composites. The effect of wood fiber concentrations and compounding temperature on the mechanical properties of composites, prepared using MAPP as the coupling agent, was investigated. In the sample preparation, four levels of fiber loading (10, 20, 30, and 40 w/w%) and three compounding temperatures (180, 190, and 200oC) were used. The results revealed that the major changes in composite properties occurred at fiber contents above 30%. The results clearly showed that the fiber loading of 30 and 40 w/w% at 190oC provided adequate reinforcement to increase the tensile and flexural strength of the composite. The modulus also increased with increasing fiber content, because poplar wood fibers are believed to be more rigid than polymer. However, the addition of wood fibers resulted in the reduction of both elongation and impact strength properties of the composites. The FTIR spectroscopy showed that the polymer was bonded to the fibers by ester linkages and hydrogen bonds at 1705–1735 cm-1