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    Ammonium zeolite and ammonium phosphate applied as fire retardants for microcrystalline cellulose filled thermoplastic composites
    (Elsevier Sci Ltd, 2019) Cavdar, Ayfer Donmez; Torun, Sevda Boran; Ertaş, Murat; Mengeloglu, Fatih
    In this study, mechanical, thermal, fire and morphological properties of thermoplastic composites filled with fire retardants (FRs) and microcrystalline cellulose (MCC) were investigated in detail. The composites were produced through the extrusion + injection molding methods using MCC, FRs and high density polyethylene (HDPE). Based on the composites dry-weights, 10%wt. of mono ammonium phosphate (MAP), ammonium zeolite (AZ) or natural zeolite (NZ) were incorporated into polymer matrix for improving reaction of fire of the composites, and their effects on technological properties were evaluated. MAP had a positive effect on tensile and flexural moduli of the composites whilst tensile strength, elongation at break and impact strength properties of the composites were decreased. The highest tensile and flexural strength values were obtained from HDPE/MCC/AZ samples, respectively, 22.13 MPa and 29.93 MPa. The minimum value for impact strength was obtained from HDPE/M/MAP5/AZ5 composite (1.68 kJ/m(2)) whereas the maximum value for impact strengths were achieved from control HDPE composite (5.15 kJ/m(2)) and HDPE/MAP10 (3.30 kJ/m(2)). Flexural strength and flexural modulus values of all HDPE composites were higher than the requirement by the ASTM D 6662 standard for polyolefin based plastic lumber decking boards. As the MCC content increased, the initial, maximum and final degradation temperatures of HDPE composites have not been influenced greatly. Thermogravimetric and differential scanning calorimetry analyses showed that the maximum rate weight loss temperature and the crystalline features of HDPE have not been significantly influenced by addition of MCC. Limiting Oxygen Index (LOI) level and charring increased when FRs were incorporated into polymer matrix. In addition, the burning rates of HDPE/MAP10 and HDPE/MCC/MAP5/AZ5 composite were slowed down by 64% and 62%, respectively. It was found that no burning in HDPE/MCC/MAP10 was observed composite during the horizontal burning test. Especially; HDPE/MCC/MAP samples can be used for building products because they meet the CC1 (plastic materials that have a burning extent of 25 mm or less where tested at a nominal thickness of 1.5 mm, or in the thickness intended for use, in accordance with ASTM D 635) class requirements of international building code which means a model building code improved by the International Code Council. In the light of obtained results, it was specified that use of FRs improved morphological, thermal and reaction of fire of the MCC filled HDPE composites.
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    Effects of halloysite nanotube on the performance of natural fiber filled poly(lactic acid) composites
    (Wiley, 2019) Ertaş, Murat; Altuntas, Ertugrul; Cavdar, Ayfer Donmez
    Poly(lactic acid) (PLA) derived from renewable resources is an alternative to petroleum-based polymers. In this work, natural fiber filled PLA-halloysite nanotube (HNT) composites were prepared using melt blending followed by compression molding. Maleic anhydride grafted onto PLA (MA-g-PLA) was used to improve the interfacial bonding quality between hydrophobic and hydrophilic phases in the natural fiber filled PLA-HNT composites. The performance properties of the natural fiber filled PLA-HNT composites were characterized by tensile, flexural and impact tests, thermogravimetric analysis, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). DSC results showed that the loading of HNT could promote cold crystallization, and the improvement of crystallinity of the PLA-HNT composites was by 16% with the addition of MA-g-PLA. The flexural and impact strengths of PLA-HNT composites were not affected adversely up to 10 phr of HNT loading, but tensile strength of PLA-HNT composites decreased gradually. In addition, numerous agglomerates of the nanotubes for PLA-HNT composites with 15 phr loading of HNT were detected with SEM micrographs. However, moduli of elasticity of PLA-HNT composites enhanced by 40% with increment of HNT loading in polymer matrix. Based on the findings, HNT could be used as nanofiller up to 10 phr in PLA matrix.
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    Limited oxygen index levels of impregnated Scots pine wood
    (Elsevier, 2013) Dizman Tomak, Eylem; Cavdar, Ayfer Donmez
    In this study, effect of various concentrations of boron powder, mixture of boric acid and borax, fireproof agent based on liquid blend of limestone, and silicon oil on limited oxygen index levels (LOI) of S. pine wood was investigated. Wood samples were first vacuum treated with the preservatives, and then were subjected to leaching procedure. Samples treated with fireproof agent showed the best results for improving the fire retardancy of wood, furthermore, samples treated with 25%, 50% and 100% of the solution did not burn. Leaching did not considerably change the LOI of wood samples treated with boron powder and silicon oil; however, LOI levels of samples treated with the mixture of boric acid and borax and fireproof agent were affected by leaching procedure probably arising those preservatives did not chemically bond to main wood components. All treatments improved fire retardancy of samples despite some amount of preservatives leached out from wood. (C) 2013 Elsevier B.V. All rights reserved.
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    Long-Term Leaching Effect on Decay Resistance of Wood-Plastic Composites Treated with Boron Compounds
    (Springer/Plenum Publishers, 2018) Cavdar, Ayfer Donmez; Dizman Tomak, Eylem; Mengeloglu, Fatih
    In this study, water absorption, thickness swelling and decay resistance of thermoplastic composites treated with three types of boron compounds was investigated. Spruce wood flour was treated with boric acid (BA), borax (BX) and mixture of BA-BX, and then was reinforced at two loading rate (20 and 40 wt%) in polymer matrix. Decay test of the composites was performed using with a brown rot fungus Coniophora puteana and a white rot fungus Trametes versicolor both for leached and unleached samples. The morphologic evaluations of decayed samples were done by scanning electron microscopy. Composites containing higher wood flour loading resulted in increased water absorption, thickness swelling, weight loss and moisture content. Fungal decay susceptibility of WPCs was influenced by leaching test for 60 days. Boron compound treated composites showed higher weight loss and moisture content than controls in decay test. All tested performance parameters were considerably increased in BX containing composites.
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    Mechanical characteristics and hydrophobicity of alkyl ketene dimer compatibilized hybrid biopolymer composites
    (Wiley, 2021) Caylak, Sena; Ertaş, Murat; Cavdar, Ayfer Donmez; Angin, Naile
    In this study, the effect of alkyl ketene dimer (AKD) on the mechanical and physical properties of natural fiber (NF) and glass fiber (GF) reinforced poly(lactic acid) (PLA) composites were investigated in detail. The hybrid PLA composites were manufactured by extrusion method followed by hot press molding. AKD was used to improve the hydrophobicity of hybrid PLA composites and compatibility of NF and PLA in the polymer matrix. The tensile and flexural tests, thickness swelling, water absorption, and contact angle measurements were accomplished for determining the performance of the hybrid PLA composites. The surface morphology of the hybrid PLA composites was also performed by scanning electron microscopy. The incorporation of AKD and NF into PLA matrix improved the mechanical strengths by 40% and above compared to those of samples without AKD. But, tensile and flexural moduli decreased as 7% and 14% of the samples with NF and AKD, respectively. Contact angle was higher for the hybrid PLA composites with AKD compared with the composites without AKD. However, the results revealed that in the presence of GF, AKD had no significant effect on overall properties of the hybrid PLA composites. In the light of the findings, AKD may have a potential usage as coupling agent in the NF filled PLA composites.