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Öğe Atmospheric pressure plasma jet treatment of wheat straw for improved compatibility in epoxy composites(Wiley, 2018) Huner, Umit; Gulec, Haci Ali; Huner, Irem DamarThe aim of this study was to investigate the effects of an atmospheric-pressure gas plasma jet treatment on the interior and exterior surface characteristics of wheat straw and on the mechanical properties of epoxy composites reinforced with wheat straw. Dry air was used as the process gas in the plasma system. A distance between the nozzle and the substrate surface (DNSS) of 35mm was determined as the most effective parameter enabling remarkable decreases in the gamma(p)(S) (surface energy) values of both the interior and exterior surfaces of virgin wheat straw. Increased intensities of the peaks related to carbon-rich species and 11% to 43% decreases in the oxygen/carbon ratios on the surfaces confirmed the more hydrophobic nature of the plasma-treated wheat straw. A further increase in the DNSS decreased the effectiveness of the plasma treatment, while a decrease in the DNSS caused an inverse effect on the gamma(p)(S) value, probably due to the etching effect of the plasma action, which was supported by the atomic force microscopy analysis. The overall results indicated that the increased hydrophobicity and valley-like occurrences without sharp pits created by the plasma action improved the compatibility of the wheat straw with the epoxy matrix, which contributed to superior mechanical properties of the composites. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45828.Öğe Effect of Chemical Surface Treatment on Flax-Reinforced Epoxy Composite(Taylor & Francis Inc, 2018) Huner, UmitThe aim of this study is to examine the impact of surface modification on properties of flax fiber and flax-reinforced composites. For this purpose, acetic anhydride, sodium hydroxide, and silane were used to treat surface of the flax fiber. The effects of treatments on fiber were investigated by using contact angle, attenuated total reflectance-Fourier transform infrared, atomic force microscopy (AFM), and scanning electron microscopy (SEM). Contact angle and AFM results revealed that sodium hydroxide-treated flax fibers have higher adhesion force on the fiber surface. Particularly, NaOH treatment improved the mechanical properties of the epoxy matrix composite.Öğe Effect of chemical treatment and maleic anhydride grafted polypropylene coupling agent on rice husk and rice husk reinforced composite(Amer Scientific Publishers, 2017) Huner, UmitThe aim of this paper is to investigate the effect of chemical treatment and the maleic anhydride grafted polypropylene (MAPP) coupling agent on rice husk and rice husk reinforced composites. Rice husk treatments were performed by using sodium hydroxide ( NaOH) and propyl-trimethoxy-silane. Surface energy and adhesion values were estimated by using AFM. The NaOH treatment showed the most compatible adhesion force and work value (45 nN and 238 mJ/m(2)) to obtain a good interface with the polypropylene matrix. AFM and FTIR investigations revealed that NaOH mostly has a dissolving effect and silane has a coating effect on rice husk surface treatment. Water absorption value of composites was improved by chemical treatment and MAPP coupling agent. While MAPP provided an improvement in tensile and flexural properties, chemically treated husks caused a slight change in mechanical properties according to neat PP.Öğe Effect of gas type and application distance on atmospheric pressure plasma jet-treated flax composites(Sage Publications Ltd, 2017) Huner, Umit; Gulec, Haci Ali; Damar Huner, IremThis study reports on the effect of atmospheric pressure plasma jet treatment on the flax fiber and flax-reinforced epoxy. The atmospheric pressure plasma jet was carried out by using four different gasses and various application distance in the range of 30-40mm. The treatments were investigated by means of contact angle, attenuated total reflectance-Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy and mechanical tests. Depending on the application parameters, the rate of increase in water contact angle varied from 49% to 92%. While atomic force microscopy and scanning electron microscopy investigations exhibited changed surface morphology, FTIR presented interactions at the molecular level. Improvement in mechanical properties was obtained for all atmospheric pressure plasma jet applications, while the increase in tensile strength in the composite material reached 180%, and the increase in flexural strength was 140%. The atmospheric pressure plasma jet method, according to similar plasma applications, came to the forefront with the short processing time and the intensity of the effect it created.Öğe THE EFFECT OF THE WELDING PARAMETERS AND THE COUPLING AGENT ON THE WELDING OF COMPOSITES(Inst Za Kovinske Materiale I In Tehnologie, 2016) Erdogan, Selcuk Ertugrul; Huner, UmitThis paper presents an experimental investigation of the welding of a glass-fiber-reinforced PP composite. The goals of this paper are to investigate the issues of local changes of the welding strength that depend on the heating time and the coupling agent (MAPP). Composite samples were prepared by using an extruding (for mixing) process and a hot-press method. The PP matrix was reinforced by unidirectional short glass fibers. The welding process for the specimens was carried out using a non-contact heated tool butt welding process. Tensile and fatigue tests were conducted to investigate the effects of the heating time parameter and the coupling agent. The highest weld strength dependent on the heating time was achieved with 94 % relative to the base strength of the material. The fatigue behavior of short-fiber-reinforced thermoplastic composites (polypropylene/20 % of volume fractions of E-glass fiber) is presented in terms of stress versus the number of cycles to failure. The specimens were fatigue tested at various percentages of their static tensile strengths at a load ratio R = 0.1 and frequency f = 5 Hz. An indefinite fatigue life was obtained at 35 % of the static damage initiation load for glass-fiber-reinforced specimens. Then, these specimen's maximum welding strengths and fatigue properties that were dependent on the heating time were compared.Öğe EFFECT OF WATER ABSORPTION ON THE MECHANICAL PROPERTIES OF FLAX FIBER REINFORCED EPOXY COMPOSITES(Lublin Univ Technology, Poland, 2015) Huner, UmitFlax fiber reinforced epoxy composites were subjected to water immersion tests in order to study the effects of water absorption on the mechanical properties. Epoxy composites specimens containing 0, 1, 5 and 10% fiber weight were prepared. Water absorption tests were conducted by immersing specimens in a de-ionized water bath at 25 degrees C and 90 degrees C for different time durations. The tensile and flexural properties of water immersed specimens subjected to both aging conditions were evaluated and compared alongside dry composite specimens. The percentage of moisture uptake increased as the fiber volume fraction increased due to the high cellulose content. The tensile and flexural properties of reinforced epoxy specimens were found to decrease with increase in percentage moisture uptake. Moisture induced degradation of composite samples was significant at elevated temperature.Öğe Functionalized Multi-Walled Carbon Nanotubes and Micro Cellulose Reinforced Poly (Vinyl Alcohol) Hybrid Composite Films: Characterization and Reprocessing Performance(Gazi Univ, 2019) Huner, UmitThe aim of this research paper was to investigate the synergetic effect of micro cellulose and multi-walled carbon nanotubes (MWCNTs) combination on physicochemical, mechanical and reprocessing performance of Poly (Vinyl Alcohol) hybrid composite films. The hybrid composite films production was carried out by the solution casting method, and the reprocessed films were produced using defective (torn, faulty) films from primary production by the same method. The combined use of MWCNTs and micro cellulose improved the hydrophobicity approximately 85% in ratio. After the reprocessing, decreased intensities of the peaks in the FTIR and Raman results confirmed the reduced molecular interaction between all components of the hybrid composite film, moreover, SEM and TEM revealed the negative defects such as agglomeration which caused mechanical strength decrease. The tensile strength of PVA hybrid composite films loaded cellulose/MWCNTs, reached 97 MPa strength value and elongation at break decreased to 33% according to the neat PVA film. The study results revealed that hybridization had a remarkable impact on improving characteristic properties of composite films and reprocessing process might have been compatible with solution casting method.Öğe Physical and mechanical properties of PP composites based on different types of lignocellulosic fillers(Journal Wuhan Univ Technology, 2018) Erdogan, Selcuk; Huner, UmitThe presents preparation and characterization of different types of lignocellulosic fillers (pine wood saw-dust/ walnut shell flour/black rice husk powder) reinforced polypropylene composites were presented. The effect of MAPP as coupling agent (4wt%) on the physical and mechanical properties was also investigated. Polypropylene composites were prepared at different rates of filler/matrix (wt%) by using extrusion (for melt blending) and hot compression molding process. Maximum values of tensile and flexural strength were obtained as 26.1 and 43.4 MPa, respectively, whereas the elongation at break value was 4.11% at 10% pine wood sawdust reinforced PP. Tensile and flexural modulus of composites reached the maximum values as 3855 and 3633 MPa with the composite of 30% walnut shell flour reinforced PP. Characterization of composites was carried out by using tensile test, flexural test, FT-IR, and SEM.
