Mechanical conversion of wood and wooden fittings
Vahid Sokhandan; Hamidreza Mansouri; Mohammad Dahmardeh Ghaleno; Mohammad Shamsian
Abstract
Background and Objectives: Historical wooden constructions clearly depict the identity, architecture, culture and lifestyle of the people of a period of history and are available to future generations as precious treasures. Therefore, the disconnection of the joints of historical wooden constructions ...
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Background and Objectives: Historical wooden constructions clearly depict the identity, architecture, culture and lifestyle of the people of a period of history and are available to future generations as precious treasures. Therefore, the disconnection of the joints of historical wooden constructions is a big problem to preserve these valuable works in the long term. This research was carried out with the aim of improving and strengthening polyvinyl acetate (PVAc) adhesive using using nanocellulose fibers (NFC) and glass nanofibers (GNF) to improve the joints of the tongue and groove in the traditional beech wood constructions.Materials and methods: In this research, in order to study the effects of reinforcements on the properties of PVAc adhesive, NFC and GNF were investigated at three different levels including 0, 3, and 6% based on the dry weight of the adhesive (9 treatments; each treatment with 3 repetitions). The connection of the palate and the tongue using polyvinyl acetate glue without NFC and GNF were considered as control samples. After preparing the samples, quantitative and qualitative tests including tensile strength, bending strength (modulus of rupture and modulus of elasticity), accelerated aging test, FTIR spectroscopy and evaluation of the samples using electron microscope scanning (SEM) was done.Results: According to the results, there was a significant difference between the studied treatments in terms of tensile strength and modulus of rupture and modulus of elasticity (P<0.05). Among the examined treatments, the highest amount of tensile strength (13.9 MPa), modulus of rupture (130.5 MPa) and modulus of elasticity (11785.36 MPa) were observed in PVAc treatment modified with 3% CNF and 3% GNF. In addition, the results showed a significant difference between the treatments in terms of accelerated aging rate (P<0.05). The lowest rate of accelerated aging (4.0) was observed in PVAc treatment modified with 3% NFC and 3% GNF. FTIR spectroscopy showed that when CNFs are inserted into the PVAc polymer matrix, hydrogen bonds are formed between the hydroxyl groups (OH) of polymer chains and the hydroxyl groups of nanocellulose, which causes the formation of coherent three-dimensional networks. Also, according to the observations from scanning electron microscope (SEM), it was found that CNFs and GNFs were relatively well dispersed in the PVAc polymer matrix.Conclusion: This study showed that by adding 3% NFC and 3% GNF to PVAc adhesive, the mechanical properties of joints in beech wood structures increase. Considering this issue, it is recommended to use a combination of cellulose nanofibers (NFC) and glass nanofibers (GNF) in order to improve the resistance properties of joints in traditional wooden structures.
Abdolah Elyasy; Taghi Tabarsa; Hamidreza Mansouri; Alireza Shakeri
Abstract
Researches on antimicrobial coatings to protect surfaces from remnants of microorganisms on the surfaces in the environment that can lead to the spread of diseases in human societies, has attracted a remarkable interest. In this regard, the effects of chitosan nanofibers and clay nanoparticles (sodium ...
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Researches on antimicrobial coatings to protect surfaces from remnants of microorganisms on the surfaces in the environment that can lead to the spread of diseases in human societies, has attracted a remarkable interest. In this regard, the effects of chitosan nanofibers and clay nanoparticles (sodium montmorillonite) on antibacterial properties of melamine coatings were investigated. Urea formaldehyde and melamine formaldehyde resins were prepared by adding nanomaterials to each of them 1% by weight using a mechanical-ultrasound mixing method. The distribution and presence of nanomaterials in the resin and the antibacterial properties of melamine coatings were studied. To investigate the antibacterial properties of melamine coatings prepared, two type Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) were used. The results of X-ray diffraction and field-emission electron microscopy images, confirmed the proper distribution of chitosan nanofibers and clay nanoparticles in the polymer. The results also showed that by adding nanomaterials to the resins used in the melamine coating, the antibacterial properties of the coatings can be remarkably improved. On the other hand, the study of antibacterial properties of coatings showed that chitosan nanofibers had stronger antibacterial properties than clay montmorillonite Na+ nanoparticles.
