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    Blast furnace slag or fly ash filled rigid polyurethane composite foams: A comprehensive investigation
    (Wiley, 2019) Akkoyun, Meral; Akkoyun, Serife
    Ground granulated blast furnace slag (BFS) and fly ash (FA) are iron-making industry and power plant byproducts, respectively. Although their use in concrete is quite common, investigation of the effects of these inorganic compounds on polymer properties is quite new, and their use as fillers in polymer foam composites has not yet been really explored. Their properties, such as high electrical resistivity, make them a good asset for use in rigid polyurethane foams that are widely used for insulation. In this study, a comprehensive investigation of the effect of BFS and FA on morphology, electrical and thermal conductivity, and rheological and mechanical properties of water-blown rigid polyurethane foams was performed. The relationship between these properties was examined. A relative enhancement of the properties is observed for filled foams, especially up to the percolation threshold. The results highlight a noticeable effect of the electrical percolation threshold on the different properties of foams. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47433.
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    Improvement of thermal conductivity of rigid polyurethane foams with aluminum nitride filler
    (Sage Publications Ltd, 2021) Akkoyun, Serife; Akkoyun, Meral
    The aim of this work is the fabrication of electrically insulating composite rigid polyurethane foams with improved thermal conductivity. Therefore, this study is focused on the effect of aluminum nitride (AIN) on the thermal and electrical conductivities of rigid polyurethane foams. For this purpose, aluminum nitride/rigid polyurethane composite foams were prepared using a three-step procedure. The electrical and thermal conductivities of the foams were characterized. The thermal transitions, mechanical properties and morphology of the foams were also examined. The results reveal that AIN induces an increase of the thermal conductivity of rigid polyurethane foam of 24% which seems to be a relatively noticeable increase in polymeric foams. The low electrical conductivity of the foams is preserved.
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    Thermal and electrical properties of aluminum nitride/boron nitride filled polyamide 6 hybrid polymer composites
    (Wiley, 2021) Yildiz, Gorkem; Akkoyun, Meral
    The effects of boron nitride (BN) and aluminum nitride fillers on polyamide 6 (PA6) hybrid polymer composites were investigated. In particular, the thermal and electrical conductivity, thermal transition, thermal degradation, mechanical and morphological properties and chemical bonds characteristic of the materials with crystal structure of BN and aluminum nitride (AlN) filled PA6 prepared at different concentrations were characterized. Thermal conductivity of hybrid systems revealed a 1.6-fold gain compared to neat PA6. The highest thermal conductivity value was obtained for the composite containing 50 vol% additives (1.040 W/m K). A slight improvement in electrical conductive properties of composites appears and the highest value was obtained for the 50 vol% filled composite with only an increase by 3%. The microstructure of these composites revealed a homogeneous dispersion of AlN and BN additives in PA6 matrix. For all composites, one visible melting peak around 220 degrees C related to the alpha-form crystals of PA6 was detected in correlation with the X-ray diffraction results. An improved thermal stability was obtained for 10 vol% AlN/BN filled PA6 composite (from 405.41 degrees C to 409.68 degrees C). The tensile strength results of all composites were found to be approximately 22% lower than pure PA6.