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    Influences of turkey feather fiber loading on significant characteristics of rigid polyurethane foam: Thermal degradation, heat insulation, acoustic performance, air permeability and cellular structure
    (Elseiver Science Ltd, 2021) Khaleel, Mustafa; Soykan, Uğur; Çetin, Sedat
    This comprehensive study delves into the preparation and detailed characterization of rigid polyurethane foams (RPUFs) filled with varying content levels (3, 6, 9, 12 and 15 wt%) of turkey feather fibers (TFFs) fabricated from the waste feathers. TFFs-loaded RPUFs were successfully produced via one-shut free-rise method in a closed mold. The obtained foam samples were evaluated by the examination of their chemical structure (FTIR analysis), thermal degradation behavior (TGA analysis), insulating performance (thermal conductivity and acoustic tests), application potential (air permeability test) and cellular morphology (SEM). TGA analysis revealed that the incorporating of TFFs at low percentage provided the thermal stability to the foams since the strong chemical interactions were formed between TFFs and RPUF matrix, however, this effect was lost at higher contents. 17% improvement (from 0.0352 to 0.0291 W/m.K.) in thermal insulating performance was recorded at the foam sample containing 3% TFFs beyond which thermal conductivities of the specimens increased gradually and, reached to the relatively maximum value. This improvement can be explained by the presence of high numbers of uniform distributed closed cells from RPUFs and hollow honeycomb structure of TFFs in the foam matrix. As for the acoustic features, the TFFs-modified foams showed tend to increase their acoustic performance in almost all frequencies with the increasing of the TFFs percent, which is attributed to the consistent increment in the apparent densities of the foam and reduction in the cavities in the matrices. Additionally, in comparison with unfilled foam, the foams with 3 and 6 wt% of TFFs illustrated lower air permeability (12.6% reduction) thanks to TFFs acting as an additional micro-barriers restricting air passage in the matrices. Furthermore, the taken SEM images revealed that the cellular structures of the resulting foams were considerably influenced by TFF loadings. The uniform cell distribution without any defective shapes was seen at low TFFs contents, whereas the formation of distorted and inhomogeneous cellular structures, local TFFs accumulations accompanied by the regional phase separation were observed at high contents.
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    Investigation of the relation between free volume and physico-mechanical performance in rigid polyurethane foam containing turkey feather fibers: Part 2
    (SAGE PUBLICATIONS LTD, 2022) Soykan, Uğur; Khaleel, Mustafa; Çetin, Sedat; Yahşi, Uğur; Tav, Cumali
    Rigid polyurethane foams (RPUFs) were modified with 0-15 wt.% turkey feather fibers (TFFs) produced from waste turkey feathers. One-shut free rising method was used for the production of TFFs-filled-RPUFs in a closed mold. The dependence of mechanical performance and water vapor permeability (WVP) feature of the final foams on TFFs loading was evaluated with free volume change. The free volume analysis was performed via Positron Annihilation Lifetime Spectroscopy (PALS), while the mechanical and WVP characteristics were determined with the use of the universal tester machines. PALS findings showed that the incorporation of TFFs with RPUF matrix caused the considerable diminishment in the free volume due to TFFs serving as a filling material and formation of strong secondary bonds between components. Moreover, tensile strength and extension of the foams decreased with the increasing of TFFs, which caused by the occurrence of noteworthy restriction on the spatial alignment and orientation capability of polyurethane chains due to the lack of sufficient free volume allowing the chains to move freely. As for the compression tests, all the TFFsloaded RPUFs depicted substantially lower performance due to TFFs interfering with the ordered organization of isocyanate domains. Moreover, impact test results showed that the addition of TFFs into RPUF matrix brought about the insufficient impact energy delocalization throughout the matrix due to the restriction on the mobility of polymer chains. Additionally,the remarkable diminishment in WVP was recorded due to the reduction in the number of vacancies and constitution of keratin composed of roundly 60% of hydrophilic protein (especially cystine). All in all, this study established a strong links between free volume and characteristics of TFFs-loaded RPUFs.