Aysen Onen

The aim of this study is to determine the effect of sub-micron fibre web layers on sound absorption properties when they are placed on rigid substrate and flexible substrate. Elastomeric thermoplastic polyurethane (TPU) and composite TPU/PS (polystyrene) sub-micron fibre webs with both rigid glass fibre fabric reinforced epoxy composites (GFEC) and flexible polypropylene (PP) spunbond nonwovens have been examined. Elastomeric TPU sub-micron fibres and TPU/PS fibre web before and after soxhlet extraction were studied. Even though a thin layer of (less than 1 mm) electrospun sub-micron fibres were used with GFEC, sound absorption coefficient (SAC) improved from 0.1 to 0.4. Maximum SAC is drawn back to lower frequency (from 1250 to 500–630 Hz), when sub-micron fibre web is used on nonwoven. In conclusion, the mechanism of elastomeric thin sub-micron fibre webs on sound absorption for rigid GFEC and for flexible nonwoven is totally different than each other.

In this study, the hydroxyl groups of cellulose acetate butyrate (CAB) oligomer were reacted with toluene diisocyanate-hydroxyethyl methacrylate (TDI-HEMA) adduct, in order to improve properties of CAB such as flexibility, thermal stability etc. Then the obtained modified CAB oligomer was characterized by FTIR and 1H NMR analysis. UV-curable coating formulations were prepared by using the modified CAB oligomer, and then applied on cotton fabrics in order to reinforce cotton fabrics and make them durable to outdoor environments. Cotton fabrics were treated with a commercial washing detergent, alkali solution, and an enzyme prior to the UV-coating, in order to increase the adhesion between the cotton fabric and coating layer. Washed and coated fabrics were evaluated in terms of absorbency, tensile, and adhesion properties, respectively. Light microscopy was employed to observe the effects of washing processes on fibre, and to show the abrasion deformation on coated fabric. Results proved that the best washing process in fibrillation was found as enzymatic washing due to the having the highest adhesion strength and the least deformation against abrasion.

Graphene, a carbon allotrope, became a significant area of research with its superior electrical, mechanical, optical properties, etc. There are several methods to obtain graphene oxide from graphite, one of which is the Hummers method. In this study, several modifications and pre-treatments preceding the Hummers method have been employed. Three different graphene oxide fibers have been produced by three different procedures, i.e. fibers obtained by Hummers method with pre-oxidation step, modified Hummers method and modified Hummers method with pre-oxidation step. It has been observed that pre-oxidation has a significant effect on graphene oxide fiber properties produced by wet spinning process (coagulation). Modified Hummers method without pre-oxidation leads to the highest breaking strength and breaking elongation. Reduced fiber linear density, breaking strength and breaking elongation together with increased crimp were observed in graphene fiber due to the addition of pre-oxidation step.

This study focuses on the effect of different process parameters including pH of GO dispersion, hydrazine reduction, number of coagulation bath on the properties of graphene oxide (GO) fibers produced through wet spinning method. Produced GO fibers have been characterized by scanning electron microscopy, Raman, X-ray diffraction methods, and an electrical conductivity meter. Results show that pH3 hydrazine reduction causes an expansion of the fiber volume and formation of porous fiber structure with higher defects. The crystal structure of GO fibers was also observed to be affected by hydrazine reduction, leading to decreased interlayer spacing and increased crystalline size and number of layer as compared to the reference (unreduced) one. Single coagulation bath was found to result in crystal on the fiber surface because of the calcium chloride (CaCI₂) salt, which provides higher electrical conductivity than triple coagulation bath. The pH value of GO dispersion was found to influence the crystal structures of the GO fiber, resulting in lower interlayer spacing, lower crystallinity degree, and higher crystallite size in the pH5 sample as compared to that of pH3 for triple coagulation baths. The results obtained in this study are expected to contribute to and shed light for further studies on carbon-based fiber materials such as GO fiber and reduced GO fiber that can have different application fields including electronic smart textiles, graphene-based membranes, gas adsorption, energy application such as lithium ion battery, and ultrafiltration applications.

Sulphur dioxide (SO₂) is an important atmospheric pollutant, and capture of SO₂ is of great importance for the environment, human health and market. Carbon based materials, especially activated carbon, are mostly used for adsorption purposes. However, there is a notable lack on adsorption of SO₂ on graphene oxide (GO) fibers and fiber web surface. In this study, the effect of addition of activated carbon, pH of GO dispersions, hydrazine reduction and oxygen/argon plasma treatment on SO₂ adsorption of GO fiber web surface were evaluated. It was seen that GO fiber web surface with activated carbon provides high SO₂ adsorption (896 mg SO₂/g) which is very higher than many of carbon based materials presented in the literatures. Single coagulation bath increases surface roughness of fiber and provides higher functional group than three coagulation baths leading to higher SO₂ adsorption capacity.

A series of dual curable polyurethane methacrylate-based oligomers were synthesized by changing the NCO:OH ratio and then were included in adhesive formulations using trimethylolpropane trimethacrylate and tricyclodecane dimethanol diacrylate (TCDDA) as reactive diluents. The effects of NCO:OH ratio and reactive diluent type on the structural properties of UV-cured free films and adhesion properties between polyester cord/rubber surfaces were studied. The highest adhesion strength of the 103 N cm⁻¹ was obtained when the NCO:OH ratio was set as 4 and the TCDDA was used as a reactive diluent.