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    Effect of alkali treatment on composites made from recycled polyethylene and chestnut cupula
    (Wiley, 2019) Torun, Sevda Boran; Peşman, Emrah; Çavdar, Ayfer Dönmez
    The objective of this study is to investigate the effects of alkali treatment on themechanical, physical properties of cupula fibers reinforced recycled high density poly-ethylene (r-HDPE) composites. The composites were produced with different chestnut(Castanea sativaMill.) cupula fiber contents, up to 50%, and polyethylene-graftedmaleic anhydride. The mechanical, physical, thermal, and morphological properties ofthe treated and untreated samples were investigated. In addition, the Fourier transforminfrared spectroscopy (FTIR) was used toobserve the interactions and functionalgroups between cupula fiber and r-HDPE inthe composite samples. The alkali treat-ment with 5 wt% NaOH solution had an affirmative effect on the tensile and flexuralproperties. It was found that an increase of 20% in flexural strength values with up to40 wt% alkali treated cupulafiber loading in polymer matrixcomparedtothatofuntreated samples. After 5 wt% NaOH treatment, the crystallinity decreased with theincrease of the chestnut cupula fiber ratio. As excepted, the FTIR analysis showed thatthe alkali treatment resulted in removal of hemicellulose, and lignin from cupula fiber.The results revealed that the alkali treatedchestnut cupula fiber can be used success-fully in polymer composites as a natural fiber filler
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    Effect of press temperature on some properties of cement bonded particleboard
    (Universidade Federal de Sao Carlos, 2020) Yel, Hüsnü; Cavdar, Ayfer Dönmez; Torun, Sevda Boran
    It is known that there is a correlation between hydration heat and physico-mechanical properties of wood based cement panels. Cement hydration is affected by many variables, such as chemical composition, water/cement ratio, wood/cement ratio, wood chemical properties, mineral additions and producing conditions. This study mainly aimed to investigate the effects of press temperature on some properties of three-layer cement bonded particleboard made from the particles of spruce (Picea orientalis) and poplar (Populus tremula). For this purpose, a total of 16 experimental board groups with 1200 kg/m3 target density and 1/3 wood-cement ratio were produced at the press temperatures of (20, 30, 40, 50, 60, 70 and 80) °C. As cement curing accelerator, CaCl2 was used at a rate of 5 % (cement weight basis). The physical, mechanical and thermal properties of the boards were determined. The results indicated that the press temperature substantially affected the properties of cement-bonded particleboard depending on the wood species. In the light of this study, the optimum temperatures in producing of cement-bonded particleboard were found as 40 °C for poplar wood and 60 °C for spruce wood.
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    Microcrystalline cellulose addition effects on the properties of wood cement boards
    (Elsevier Ltd, 2022) Dönmez Çavdar, Ayfer; Yel, Hüsnü; Torun, Sevda Boran
    The study investigates the performance of microcrystalline cellulose (MCC) as reinforcer in cementitious wood particle products. The wood cement boards were produced with various MCC amounts, up to 30 wt % based on wood particle weight. Physical, thermal and mechanical properties of MCC added wood cement boards were investigated and compared with conventional wood cement boards. The water absorption and shrinkage of cement panels decreased at low MCC additions, but increased at high rates of MCC. The highest values of the MOR and IB of the wood cement boards were observed at 5% and 10% MCC content, respectively. When used above this ratio, the MOR values were significantly reduced. The dispersion effect of MCC depending its ratio in cement matrix was observed with scanning electron microscope. Although the possibility of overlapping of wood component (lignin) and cement hydrate [Ca(OH)2] signals due to the high decomposition temperature of lignin challenged the determination of Ca(OH)2 amount, one of the cement hydration products, TGA/DTG results demonstrated that as the MCC content in the wood cement boards increased, the decomposition amount of Ca(OH)2 increased. This indicates that mcc improved the cement hydration, compared to spruce wood. In terms of DSC results, the addition of MCC to the wood cement boards lowered the temperature and increased the enthalpy and peak height.