Levent Onal

Effect of enzymatic pretreatment on the mechanical properties of jute fiber-reinforced polyester composites

The effect of various enzyme treatments on the mechanical properties of jute fiber-reinforced polyester composites was investigated in this study. Prior to composite production, jute fabrics were treated with pectinase, laccase, cellulase and xylanase enzyme solutions with varying enzyme mixtures and treatment time according to experimental design. The comparison of NaOH and enzyme-treated samples was also investigated. Jute fabric-reinforced polyester composite samples were produced using compression molding. The effect of enzymatic and NaOH treatment on fibers and fiber-matrix interface was investigated by scanning electron microscopy study. The mechanical properties of enzyme-treated and control (without enzyme treatment) samples were evaluated by means of tensile and flexural tests. It was observed that enzymes destroyed pectin, hemicelluloses and lignin substances from the fiber bundle interface which reduced the technical fiber diameter and hence increased the fiber aspect ratio. Therefore, a greater fiber-matrix interface area was created after enzymatic treatment, which facilitated better fiber-matrix adhesion and improved mechanical properties of the composites. The data indicated that enzyme treatment can be used as an effective, cheap and environmentally friendly fiber modification method for natural fiber-reinforced composite production.

Comfort properties of functional three-dimensional knitted spacer fabrics for home-textile applications

The effect of thermal properties on the three-dimensional knitted spacer fabrics made from functional fibers (i.e. Outlast®, Coolmax®) with different fiber compositions was studied. The spacer fabrics were specifically designed for mattress ticking applications. Samples were manufactured with two fabric tightness and knit designs, and four Outlast® fiber compositions. Thermal conductivity, thermal resistance, thermal absorptivity, thermal diffusivity, and relative water vapor permeability were considered as thermal comfort properties. Alambeta and Permetest devices were used for the measurement of thermal properties. Fabric design was the leading criteria on the thermal resistance and water vapor permeability, while fiber compositions became more important on the thermal absorptivity. The contribution of Outlast® fiber on the thermoregulatory efficiency of spacer fabrics was analyzed using a differential scanning colorimeter. The thermoregulatory effect of Outlast® fiber was slightly observed in the 33% Outlast® fiber composition. Water vapor permeability of open-skin samples was higher than the closed-skin samples, which was due to the holed/meshed structure of the open-skin structure for the same fiber content and fabric construction. Statistical analysis was also performed and confirmed the contribution of each factor, including their interactions. In particular, the interaction became more significant than the main factors for thermal diffusion behavior of samples.

Mechanical Characterization of Carpet Waste Natural Fiber-reinforced Polymer Composites

This investigation deals with the property characterization of polymeric composites from abundantly available and renewable jute fibers. The aim of this article is to explore the possibility of using carpet waste jute yarn for value added fiber-reinforced composite materials and to investigate the physical and mechanical properties of these low-cost composites. Jute yarn was treated with 25 wt% NaOH solution to improve fiber—matrix interface. NaOH-treated jute yarn was crimpier, bulkier, more hairy, and flexible. The investigation of the mechanical properties of composites was performed as a function of yarn type, reinforcement form, matrix type, alkali treatment, and fiber content. For this purpose, the tensile, flexural and charpy impact tests were performed. It was found that composite samples from alkali treated reinforcement had better mechanical properties based on the investigated parameters. SEM analyses showed that alkali treatment improves bonding across the fiber—matrix interface. Jute—epoxy composites showed better tensile and flexural strength in comparison to jute—polyester composites, whereas impact strength of epoxy matrix composites were almost half that of polyester matrix composites. Composites from double ply jute yarns showed better flexural strength. Taking into account the reinforcement form, jute composites from random reinforcement form showed higher tensile strength and modulus. The study strongly suggests that the jute fiber waste-reinforced polymer composite materials are quite capable to serve as a potential cost effective, technologically viable, and attractive substitute to the conventional glass fiber composites.

Water absorption behavior of carpet waste jute-reinforced polymer composites:

This article deals with the water absorption behavior of low-cost polymer composite composed of carpet waste jute yarns and thermoset matrices (i.e., epoxy and polyester). The water absorption behavior of the composites and deviation of their flexural and impact properties after aging in distilled water were investigated. The magnitude of diffusion parameters such as n and K were evaluated to assess the mode of water transport. It was found that the composites follow Fickian diffusion behavior. Both maximum water content (Mmax) and effective diffusion coefficient (Deff) values increased with increasing fiber content. Epoxy matrix composites showed higher Mmax and D eff values when compared to those of polyester matrix composites. D eff value increased remarkably with an increase in immersion temperature, whereas temperature had relatively little impact on Mmax value. Thermodynamics of diffusion process was investigated using Arrhenius plots and the magnitude of the activation energy for the process of diffusion (E a) was evaluated. Ea increased with temperature increment, suggesting fast access of water into polymer segments at elevated immersion temperatures. NaOH treatment of jute yarns was also investigated in terms of the water absorption behavior of the composites. It was shown that alkali treatment reduces water absorption of the composites remarkably, which was attributed to interface improvement. Flexural strength and modulus of the composites decreased up to 40% and 60%, respectively, whereas Charpy impact strength increased up to 30% after 168 h of water immersion.

Dynamic mechanical and thermal properties of enzyme-treated jute/polyester composites

Dynamic mechanical and thermal behavior of polyester composites reinforced with enzyme and NaOH-treated jute woven fabrics were studied. Dynamic properties such as storage modulus (E′), loss modulus (E″) and damping parameter (tan δ) were determined in a single-cantilever bending mode. The storage modulus of the composites increased up to 110% and 130% with enzymatic and NaOH treatments, respectively. The composites reinforced with NaOH and enzyme-treated fibers showed a shift in loss modulus to a higher region when compared to untreated fiber composites. This was attributed to the increased immobilization of polymer matrix at the fiber–matrix interface as a result of pre-treatments. Tan δ pick values of the samples with treated and untreated jute fibers are fairly close indicating that all the samples showed very similar energy damping behavior. The derivative thermogravimetric and differential scanning calorimetry curves indicated that the thermal stability of the composites slightly decreased in the case of NaOH and enzyme treatments. Scanning electron microscopy pictures revealed a stronger fiber–matrix adhesion in composites with enzyme-treated fibers when compared to untreated fiber composites.

Relations between the characteristics of Angora rabbit fibre

Angora rabbit fibre is one of the finest specialty animal fibres with its well-known reputation for fineness, lightness and softness. This study evaluated the Angora fibre shape and morphology in comparison with Cashmere fibre and wool as well as the relation between characteristics of Angora fibre. Unlike other keratinous textile fibres, single Angora fibre composes of two sections named as body and head, each of which has individual surface characteristics. Differences between the scale shapes, scale length and scale frequency of Angora hair types were explained in details. Medullation in Angora fibre was explained for different types of Angora hairs defined as down, awn and bristle. This classification was done according to the fibre fineness starting from the finer one. Relation between fibre shape and comfort factor was also analyzed. The relation between mean fibre diameter (MFD), fibre curvature (FC) and percentage of medullation by volume (MEDV) for Angora rabbit fibre was not as strong as wool and Cashmere fibre. Accordingly, when Angora hair types were analyzed individually, it was observed that relation between FC and MEDV for Angora fibre was stronger than wool and Cashmere fibre. Multiple regression analysis was also performed. Diameter distribution along the snippet length (about 200µm) of Angora fibre is uneven compared to Cashmere fibre and wool.

Fundamental geometric model of 3D knitted spacer fabric

3D knitted spacer fabric is a three dimensional textile structure composing of two surface fabric layers combined by pile yarns whose thickness changed depending on the final application area. The pile yarns are alternatively bound to the cylinder and dial needles with tuck stitches during the knitting cycle. In this study, a fundamental geometric modeling is proposed to predict the yarn consumption of 3D knitted spacer fabric for home textile application. The model was proposed with very fundamental assumptions. The initial step was to follow up the yarn path in order to characterize the fabric structure. The theoretical yarn consumption was compared with the experimental value for two different fabric tightness but having the same fabric design and knit. The samples were manufactured on double-jersey circular knitting machine equipped with spacer attachment. It was found that there was only small deviation between the theory and experiment.