No abstract

Bu çalışmada, farklı lif boy/çap oranına sahip kırpılmış cam elyaflar, basınçlı hava ile açılmış elyaf demedi haline getirilmiş ve epoksi matrisin takviyelendirilmesinde kullanılmıştır. Ağırlıkça %5, %10 ve %15 oranında elyaf takviyesiyle elle yatırma yöntemiyle üretilen kompozitlere çekme dayanımı, eğilme dayanımı ve ısıl iletkenlik testleri yapılmıştır. Elde edilen sonuçlar, eş işlem parametrelerinde üretilen kırpılmış cam elyaf takviyeli kompozitler ile kıyaslanmıştır. Lif açma süresinin kullanılan kırpılmış lifin boy/çap oranına bağlı olmadığı ve lif boyunun lif açma süresi üzerinde lif çapına göre daha önemli etkiye olduğu görülmüştür. Uzun lif boyuna sahip kırpılmış cam elyafların lif açma işlemine daha hızlı cevap verdiği gözlenmiştir. Lif açma işlemi genel anlamda kompozitlerin çekme ve eğilme dayanımlarında düşüşe ancak yalıtım özelliklerinde artışa neden olmuştur. Lif boy/çap oranı 4.5 mm/13 µ olan cam elyaf tipi için, açılmış elyaf demedi kullanılarak daha düşük konsantrasyonda yüksek çekme dayanımı elde edilmesi söz konusudur. Eğilme dayanımı üzerinde lif boyunun etkisinin yüksek olduğu ve açma işlemi sonrasında, lif boy/çap oranları 3 mm/13 µ ve 4.5 mm/10.5 µ olan cam elyaf tiplerinin eğilme dayanımı davranışlarının daha tutarlı hale geldiği tespit edilmiştir. Lif açma işleminin kompozitlerin ısıl iletim katsayılarının düşmesinde etkili olduğu ve kompozitleri daha yalıtkan hale getirdiği görülmüştür.

This study examines the effect of different patterns on aesthetic properties, air permeability characteristics and mechanical performance of woven fabrics constructed with 100% cotton ring spun yarns. Weaving process were proceeded by using 28/2 Ne combed warp and 32/2 Ne carded weft yarns with identical manufacturing parameters. Fabrics with 5 dissimilar patterns were obtained and 5 measurements were done for each pattern type. Average yarn floats, crimp percentage and yarn settings were calculated and fabric thickness, abrasion resistance, air permeability and bi-directionally tensile strengths of these fabrics were tested. Test results showed that increasing the numbers of floating yarns made fabric more air-permeable but less resistant against to applied mechanical forces. Besides, it caused to increase in fabric thickness. All test results were statistically evaluated by ANOVA and Duncan comparison tests and it was seen that the effect of weave pattern was at significance level of p<0.001. Air permeability characteristics of wovens can be easily and inexpensively arranged by pattern effect. In order to satisfy mechanical and functional specifications, further studies should be performed on panama woven structures with different yarn floats.

In this study, it is aimed to observe electrospinnability of bismuth oxide (Bi2O3) microparticles via polymer solution and effect of loading on electrical insulating property of electrospun composite structure. For that purpose, polyamide 6.6 polymer (PA6.6) with high dielectric constant was loaded with bismuth oxide microparticles and it was used for coating polyester spunbonds by electrospinning technique. Morphological properties, thermal behaviors and electrical resistance of coated spunbonds were investigated. Scanning electron microscopy (SEM) and electron dispersive X-ray spectroscopy (EDX) showed that Bi2O3 was succesfully adapted into fiber structure and nano-scale PA6.6/Bi2O3 composite fibers were obtained. Thermal behaviors of coated samples were developed by increasing Bi2O3 loading according to differential scanning calorimetry (DSC) and thermogravimetic analysis (TGA) results. Addition of Bi2O3 caused remarkable increase on electrical resistance of PA6.6 electrospun surfaces. Bi2O3 /PA6.6 nanocomposite fibers are promising and good candidates for thin electrically insulating polymer-based structures for micro- or nanodimensional devices.

Polymer-based insulators have attracted much attention amongst researchers due to their various advantages such as light weightness, lower cost and ease of production. In this study, it is aimed to manufacture lightweight and thin insulator by electrospun composite fibers and to observe the effect of bismuth oxide (Bi2O3) on insulating property of polymer-based composite structure. For that purpose, polyamide 6.6 polymer (PA6.6) with high dielectric constant was doped with bismuth trioxide micro particles and it was used for coating polyester spunbonds by electrospinning technique. Morphological properties, thermal behaviours and electrical resistance of coated spunbonds were investigated. Scanning electron microscopy (SEM) and electron dispersive X-ray spectroscopy (EDX) showed that Bi2O3 was succesfully adapted into fiber structure and nano-scale PA6.6/Bi2O3 composite fibers were obtained. Thermal behaviours of coated samples were developed by increasing Bi2O3 loading according to differential scanning calorimetry (DSC) and thermogravimetic analysis (TGA) results. Addition of Bi2O3 caused remarkable increase on electrical resistance of PA6.6 electrospun surfaces. Bi2O3/PA6.6. nanocomposite fibers are promising and good candidates for thin electrically insulating polymer-based structures for micro- or nanodimensional devices.