No abstract

In this study, sound absorption and abrasion resistance performance of needlepunched nonwovens produced from blend of round polyethylene terephthalate/hexaflower polyethylene terephthalate/low melt polyethylene terephthalate fibers with various weight ratios, i.e. 50/40/10, 40/40/20, 70/20/10, 50/30/20, were reported. The carded webs were bonded by needlepunching at two punch densities, i.e. 400–500 punches/cm2 and penetration depths, i.e. 11-6-6 and 13-8-8 mm, then passed through an through-air thermal bonding oven to melt low melt polyethylene terephthalate fibers within the samples. Design of experiments was planned according to Taguchi method, and an optimum sample, produced according to optimum production levels, was determined. In order to further improve the sound absorption and abrasion resistance performance, as a first approach, a low denier nonwoven top layer was combined with the optimum sample. As a second method, samples were back coated with a styrene butadiene resin and the changes in sound absorption were analyzed. The effect of production parameters on sound absorption and abrasion resistance was analyzed using a Minitab statistical software. As a result, fiber blend ratio, penetration depth, and areal density significantly affected sound absorption and abrasion resistance performance of nonwoven samples. On the other hand, punch density was found to be statistically insignificant over sound absorption and abrasion resistance. The optimum sample reached to a sound absorption coefficient value of 0.273 at 2000 Hz, and showed a fiber loss percentage of 1.55% and was found to be a suitable facing material for automotive carpet applications.

In this study, the layered nanoclay was employed to impart ultraviolet (UV) protection functionality for electrospinning thermoplastic polyurethane (TPU) nanofibrous mats. This study is among the very rare studies which uses Montmorillonite (MMT) clay for UV protection. Due to its known UV protection property, titanium dioxide (TiO2) was used solely for comparison with MMT clay and as a blend with MMT for investigation of its synergetic effect with nanoclay. The morphology and chemical structure of virgin and nanoclay-loaded nanofibers were characterized via Scanning Electron Microscopy (SEM) and Fourier Transform Infared Spectroscopy (FTIR). Incorporation of TiO2 significantly improved UV protection performance of TPU electrospun nanofibers, as expected. UV protection factor (UPF) of electrospun mats including nanoclay was found as high as that of the ones including TiO2.Therefore, the study revealed that the clay has a considerable potential for producing nanofibrous layers with UV protection. Such a nanocomposite structure could be potentially employed as a layer in a multilayered technical textile such as tents, sun protective covers for automobiles, blind curtains, etc. This study proposed an eco-friendly and viable alternative to TiO2 which is a well-known material for its UV protection.

In this study, the effects of both D-lactide content, that is, the change in PLA crystallizability, and molecular weight of polylactide (PLA) on its electrospinning behavior, along with thermal and mechanical properties of the electrospun mats were investigated. Although the effect of D-lactide content on processability of PLA has been studied in extrusion, thermoforming, foaming, and melt spinning, it has not been explored in electrospinning. The current study aimed to analyze electrospinnability of three different PLA grades; two amorphous with high and low molecular weights (i.e., aPLA-H and aPLA-L) and a semicrystalline with a high molecular weight (cPLA-H). PLAs were dissolved at different concentrations in chloroform (CHL)/dimethylformamide (DMF) at various volume ratios. Due to its high crystallizability and molecular weight, coarser nanofibers of cPLA-H were produced from solvents with high CHL content (≥75%), resulting in highest water vapor transmission rate (50,000 g/m2.day) of mats. aPLA-H revealed coarser nanofibers than that of aPLA-L due to its higher molecular entanglement. Although the increase in DMF content in the solvent hindered dissolving and electrospinning of cPLA-H, it caused the refinement of nanofibers in amorphous PLAs. Despite similar tensile strength, cPLA-H showed higher elongation at break (∼69%) than that of aPLA-H (∼59%) possibly due to the existence of some beads within the fibers in aPLA-H. Storage modulus of electrospun cPLA-H was also higher (∼15MPa) than that of other samples (∼10–12 MPa) due to high content of crystallinity (∼37%) while aPLA-L revealed the lowest storage modulus (∼10MPa) due to its amorphous structure and low molecular entanglement.

In this study, a colorimetric pH indicator was developed using nanofibrous mats of polylactide (PLA) including turmeric, a natural dye. Firstly, nanofibrous mats were produced by dissolving PLA at different concentrations in chloroform (CHL)/dimethylformamide (DMF) at various volume ratios, and morphological analysis was performed. Subsequently, turmeric was added at a concentration of 2% wt. to the polymer solution having a PLA concentration of 10% in 75/25 CHL/DMF, and nanofibrous pH indicators were produced. Then, pH indicators containing turmeric were immersed into pH buffer solutions (pH 1, 4, 7 and 10), and color variations were measured using a spectrophotometer. It was foreseen that the produced pH indicators have the potential to be used in intelligent food packaging applications.