جستجوی مقالات مرتبط با کلیدواژه « پلی وینیل استات » در نشریات گروه « صنایع چوب و کاغذ »

Poly vinyl acetate (PVAC) adhesive is one of the most important adhesives in wood and furniture industry, which has many advantages such as low cost, environment friendliness and non-toxicity. However, it has some disadvantages such as low water resistance and poor boning strength. In this study, the effect of nano silica (NS) on the properties of poly vinyl acetate adhesive was investigated. The adhesive formulation with different NS contents (2, 3 and 4%) was added to the PVAC. The structure of the prepared adhesive samples was studied by FT-IR and XRD. We used the wood of Acer tree (Acer cappadocicum) to make joints in this study. Two standards of D882 and ASTM D905 were used for tensile and shear tests, respectively. Results showed that adding NS to PVAC enhanced the tensile strength of films. For example, the tensile strength of prepared films was increased by 30% after adding 4% of NS. Moreover, shear strength test showed that NS up to 3% can improve PVAC bond strength. Viscosity results showed that increasing the weight of NS up to 3% to PVAC glue lead to an increase following a decrease in the viscosity

The aim of this study was investigation of the performance of mitered corner joints (L-shaped) reinforced by fibers reinforced polymer (FRP) at maximum stress area under diagonal compression loading. In This way, structural performance of constructed corner joints of two species of beech and fir reinforced by fiber reinforced polymer at polymeric matrix of epoxy with one and two layer of carbon and glass fibers and were investigated. After construction of the mitered joints with wooden dowel and polyvinyl acetate adhesive, the joints were reinforced with FRP composites and then were subjected to diagonal compression loading. Results have indicated that reinforcing layers prevent joint opening, however, failure was occurred at the joint by peeling fibers from wood surface or members fracture near the joints by stress concentration. The results of variance analysis showed that the independent effect of species of joint members and numbers of fibers layer were significant at 95% confidence level. The results showed that use of beech wood in comparison with fir wood, composites reinforced by carbon fibers compared to glass fibers, as well as the use of two layers of fiber compared to 1 layer of fibers, exhibited better performance in constructed joints. The joints made with beech wood and reinforced with 2 layers of composites reinforced by carbon fibers showed the best performance under diagonal compression loading.

Fiber Reinforced Polymer (FRP) has become one of the most popular methods in the reinforced, repair and rehabilitation of structure due to its ease of application and the special physical characteristics. Both destructive and nondestructive assessments have been used to test the characteristics and durability of FRP in order to investigate the condition of the structure. The aim of this research was to investigate the structural performance of corner joint reinforced with fiber reinforced polymer (FRP) composite under diagonal tension load. Constructed joints from two wooden species of beech (Fagus orientalis) and fir (Abies alba), were reinforced with reinforced composites of one and two layer of carbon and glass fibers and then they were tested under diagonal tension load. The miter corner joints were made with wooden pin and polyvinyl acetate adhesive. The fibers lay-up was done manually. Epoxy resin was used as a polymeric matrix. Result of investigation indicated that use of beech wood in comparison with fir exhibited better results. In addition, glass fibers have shown better performance than carbon fiber as reinforcing agents.  Inspection of diagonal tension specimens after failure have indicated that using of FRPs on the surfaces of L-shaped miter prevent joint opening, however, failure was occurred at the joint by increasing of load and vertical displacement and the general wood weakness in tension perpendicular to the grain and shear parallel to the grain at dowels site due to stress concentration. Also the results showed that the miter corner joint made with beech species and two layers of glass fibers had the highest stress carrying capacity.

In this study, the utilization of fibers recycled from MDF wastes and waste papers for manufacturing fiberboards was investigated. The proportion of waste paper to recycled fibers from MDF wastes was 70/30 and 50/50. Also the effect of utilization of poly vinyl acetate adhesive on properties of boards was investigated. Boards were manufactured at density of 0.3 g/cm3 and dimension of 30×30×1.2cm. Practical properties of boards including thickness swelling, bending strength, modulus of elasticity and internal bonding were measured. The results showed that the utilization of adhesive can improve all of board properties. Change in proportion of recycled fibers to waste paper had different influences on various properties of manufactured fiberboards. The proportion of 70/30 of waste paper to recycled fibers from MDF wastes led to improving bending strength and modulus of elasticity of fiberboards, while the manufactured boards from proportion of 50/50 had better results about thickness swelling and internal bonding. Overall, it can be concluded that recycled fibers from MDF wastes mixed with waste paper can successfully utilize in producing fiberboards.

The aim of this study is to investigate the performance and fracture monitoring of dowel-welded joints by micrographs of scanning electron microscopy (SEM). In this regard, joints with hornbeam (Carpinus betulus) and fir (Abies alba) members were constructed by using hornbeam smooth and grooved dowels with diameter of 10 and 12 mm. The joint members were cut according to EN 326-1 standard and after assembling, the joints were subjected to the tensile test according with EN 319 standard. The results showed that effects of independent variables on tensile strength was significant. The investigation of the scanning electron microscope images from the fracture zone of the welded joint member demonstrated that not only the fracture at the joint zone was not occurred, but also the welded area between the dowel and the joint member exhibited greater strength in comparison with wooden members during tensile loading. Also, the investigation of the image obtained from the SEM showed that the components of the welding line did not remain on the dowels with smooth surface, and the dowel surface was also affected by micro cracks, but the surfaces of grooved dowels were sound and part of the welding line was observed on the dowels. According to the results of this study, compared to conventional adhesives, using of welding in making joints with small diameter and smooth dowel, not only provides a joint with the proper structural performance, but also it provides optimum utilization of wood in making joint. This leads to raw materials savings, cost reduction of raw materials preparation and reduction of jointing time which altogether cause to reduce production costs.

In this research, the effect of Polyvinyl acetate (PVAc) adhesive reinforced with modified carbon nanofibers (CNF) were studied in three levels (0%, 0.4%, 1.5%) on the strength properties of joints commonly in the furniture industry. Modified carbon nanofibers were used as chemically modified surface to improve the dispersion in polymer matrix. The bonding of the test specimens were made using of cut out medium density fiber board (MDF) pieces with desired dimensions and dowel wooden with 6, 8 and 10 mm in diameter, and penetration depth at three levels using polyvinyl acetate adhesive reinforced with modified carbon modified nanofiber. Totally, we have 27 treatments with three replicates. The evaluation of the bending moment capacity of test specimens made with freshly formulated adhesive carried out and the effect of other variables was performed on the joints made under tensile loading at a speed of 3 mm/min. The results showed that increasing the weight percent of carbon nanofibers, the diameter of the wooden dowel and the penetration depth and the moment capacity compared to the control samples was increased by 1.6, 1.5 and 1.3 times, respectively. The 0.4% w/w carbon nanofibers, 10 mm diameter and L3 wooden dowel penetration depth had the greatest effect on the strength of the joints.

Joints in furniture and wooden structures due to the highly sensitive bearing load are today one of the most important scientific topics. The most recent method proposed to build wooden joints in Europe and the United States is a method eco-friendly, without using any type of adhesive substance or connector, called "wood welding". In the present study, the effect of diameter and dowel surface on the tensile strength of softwood joints (made with dowel) was investigated using two wood welding and glue bonding. Polyvinyl acetate glue (PVA) for bonding, species Fir (Abies alba) for members joint and species Hornbeam (Carpinus betulus) for connector dowels were selected as fixed parameters. The structure of the welded surfaces was analyzed using scanning electron microscopy (SEM). The results of the tensile strength test showed that parameters of diameter and type of dowel surface have a significant effect on the tensile strength of softwood joints in both joint methods.

The insertion of dowels into solid wood for furniture has been used for centuries. Recently, this simple technology has been upgraded. The objective of the research was to evaluate and compare the tensile strength of the joints made of wood dowel through new method “wood welding” and classical method “using of glue”. Variables included dowel joints method (welding joint and joint with glue), dowel diameter (10 and 12 mm) and dowel surface (smooth and grooved). Members joint and dowel wood were hornbeam species (Carpinus betulus) and the used glue was polyvinyl acetate (PVA). The results showed that the types of joints, diameter and surface dowel, have significant effect on the tensile strength, so that welded joints, dowel diameter 12 mm and dowel grooved surface has the most tensile strength to other samples. The results also showed that in all cases, the strengths of the joints made by welding was more than the joints made by PVA glue.

The objective of this work was to compare barrier property of biodegradable coatings on two base papers. Two different paper grades differing in structure (Kraft liner and printing & writing papers) were used. The papers are made in Mazandaran wood and paper industry. Coating materials with 30% solid content, included clay (100 parts) and cationic starch (12 parts), and they were mixed with two binders (PLA 10 parts and PVA 10 parts) for two formulations. The immersion method in both levels 1 and 2 minutes and two coating formulations were applied on papers. Then, the treated samples were dried in standard conditions of temperature (25◦C) and 54% humidity in the room. For that purpose, air resistance or porosity, thickness, mass, and Cobb60 were determined. As expected, time of treatment, reduced porosity and increased coating weight, but in terms of barrier properties, combination containing PVA was more effective than PLA. In comparison to the control group, all the treated samples had higher air resistance and water absorption, which the increment of water absorption is due to increased capillary in texture paper. The analysis of results showed that the immersion coating factors had considerable effects on performance of air resistance improvement and coating weight of papers. Then, calculated values of the thickness and density of coating were evaluated, which confirmed the status of water absorption. The treatments greatly increased the wettability of the surface by water.

Effects of screw length (2, 2.5,3 inch), wood species (beech, alder, white spruce), and two screw interval (2, 2/5 cm) on bending strength of the T-type joints were investigated. In order to fabricate the T –shaped joints, dimensions of the parts were determined as 15*5/5*2/5 cm. From the above variables, 18 combinations were reached. Four replications, and a total of 72 specimens were made and the mechanical strength of the specimens were measured by mechanical testing machine. Results indicated that the beech joints with 3-inch length screws had the highest bending strength, while the lowest bending strength was observed in spruce wood with 2-inch length screws. The study revealed statistically significant differences between the wood species, while there were not any difference between screw interval and bending resistance.