With an increase in the awareness of polymer viscoelasticity, several researchers in the textile industry have conducted rheological experiments to investigate the polymeric materials they deal with. However, the experimental results can be interpreted meaningfully when the polymeric materials are processed and analyzed based on viscoelastic theory. This review first describes the fundamental theories of linear viscoelasticity. Moreover, it provides various examples of linear viscoelastic studies on polydisperse polymer melts, polymer solutions, polymer blends, and reacting systems. The types of experiments depend on the measured viscoelastic functions. Viscoelastic functions are mathematically interconvertible within a linear viscoelastic range. However, numerical data processing is necessary to practically apply theoretical relations to experimental results. Here, we review several useful numerical methods and algorithms. We hope this review could be a helpful guide for researchers analyzing the viscoelasticity of textile materials.

The dispersibility of nanoparticles in polymer nanocomposites significantly affects the mechanical, thermal, and electrical properties of the final products. The objective of this study is to quantify the dispersibility of nanoparticles in polymer nanocomposites. Various amounts of graphene nanoparticles were introduced in polypropylene-based and polylactic acid-based resins through melt compounding. They were then injection-molded to fabricate disc-type specimens for characterizing the rheological properties of the nanocomposites. To evaluate the dispersibility of the nanoparticles in the composites, the associated storage (G') and loss (G") moduli were analyzed for plotting the G'-G" slopes. Furthermore, the Van Gurp-Palmen plot was employed for analyzing the increase in material elasticity with respect to the base resins and nanoparticle compositions.

In this study, we investigated the effects of polylactic acid (PLA) blending on the mechanical properties (such as tensile strength, initial modulus, and elongation at break) of polybutylene succinate (PBS) for improving the associated tensile properties without incorporating compatibilizers. The maximum PLA mixing content of 20% by weight was selected by studying the mean squared displacement through molecular dynamics simulation. Subsequently, the PBS/PLA blends were compounded by increasing the PLA content from zero to 20% by weight. The obtained results indicate that the tensile strength of the PBS/PLA blend increases when the PLA blend content is 15% by weight, and the initial modulus increases when the PLA blend content is 20% by weight. Furthermore, at the content of approximately 15% by weight, PLA can be blended without a compatibilizer for improving the tensile strength and initial modulus.

In this study, isothermal oxidation reactions of polyacrylonitrile-based T300 and T700 carbon fibers were conducted in air at 700 ℃ by employing a horizontal tube furnace. The oxidized fibers were examined through XRD and micro-Raman analysis for quantitatively analyzing the changes in crystallinity occurring after the oxidation reactions. The results obtained from XRD analysis corroborate that the overall crystallinity of an oxidized fiber is lower than that of the corresponding raw fiber. Observation through a scanning electron microscope indicates that a longitudinal hollow pore is formed along the fiber axis of each oxidized fiber. Additionally, since the crystallinity of the fiber core is lower than that of the sheath, the conducted micro-Raman analysis suggests that the core became oxidized first to form the longitudinal hollow pore. In this study, it was difficult to measure the depth of the longitudinal hollow pore through the fiber core. In the future, if the depth of the hollow pore can be measured at the fiber core and is optimized for developing the hollow pore, new support materials, which serve as the carriers, can be designed.

Carbon fiber is an advanced material widely used in high-tech industries because of its light weight, heat resistance, chemical resistance, excellent mechanical properties, and electrical and thermal conductivity. However, carbon fibers also have high production costs and limited disposal methods (e.g., landfills). Research is being conducted to address these problems through the recycling of carbon fibers. Among the representative recycled carbon fiber products, wet nonwoven fabrics have limitations in their mechanical properties because their structure simply consists of stacked microsized-diameter carbon fibers and a binder. In this study, the tensile strength was improved by adding cellulose nanofibrils (CNFs) during the manufacturing of wet nonwoven fabrics by mixing short-cut carbon fibers and a binder (short-cut PVA fibers). CNF bundles improve the mechanical properties by forming a complex structure via the crosslinking of carbon fibers and short PVA fibers. The tensile strength of nonwoven fabrics consisting of short carbon fibers and PVA fibers was determined to be 92 gf. On the other hand, the tensile strength of the nonwoven fabric with 10% CNF added to the binder increased by approximately 20 times to 1,808 gf. The composite with nanofiber was confirmed to be effective in forming a structure with high mechanical properties when fabricating microfiber-based nonwoven fabrics.

Polylactic acid (PLA), a biodegradable polymer, has been widely used for disposable applications as a replacement for nondegradable polymers. The decomposition of biodegradable polymers is mainly carried out by composting, photolysis, and hydrolysis under given environmental conditions. The purpose of this study is to investigate the effect of water treatment on the tensile and thermal properties of needle-punched PLA nonwoven fabrics. The PLA nonwoven fabric was immersed in water at various temperatures and treatment times. The morphology and thermal and mechanical properties of the PLA nonwovens were examined by scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and a tensile tester according to the water immersion conditions. The results showed that when the water treatment time increased, the tensile strength and tear force of the PLA nonwoven fabric decreased significantly. Crystallinity analysis showed that the decomposition of PLA nonwovens was due to molecular chain cleavage of the α and β phases. Depending on the decomposition environment, the weight reduction of PLA nonwovens by water treatment was very high, while the decrease in tensile strength was proportional to the weight reduction. Therefore, the decomposition of PLA during water treatment was confirmed to be very significant.

Strong acids, such as hydrochloric acid and sulfuric acid, are colorless and difficult to detect when leaked by accident. A chemosensor using a halochromic dye can serve as a simple and easy detection method by exhibiting different colors when exposed to acidic liquids. In this study, bromocresol purple was used as a pH-indicating dye for detecting acidic liquids. Nylon 66 woven fabric was dyed with bromocresol purple, and the dyeing properties were investigated. The pH-sensing property was also investigated by dipping the dyed nylon fabric in an acidic solution. Bromocresol purple in an aqueous solution showed maximum absorption at 433 nm with a yellow color at pH 2-4, and at 589 nm with a blue color at pH above 6. The color yield (K/S) of bromocresol purple on nylon 66 is highly dependent on the dyebath pH. When the yellow sample, which was dyed at pH 3 or less, was immersed in a solution with pH 2-3.5, its original orange color was maintained. Then, the color turned blue when immersed in a solution with pH 4-5.5. In contrast, olive or olive green samples were obtained when dyed at pH 4-6. When the sample was immersed in a solution with pH 2-3.5, the color changed to yellow. The color also changed to blue when the sample was dipped in a solution with pH 4-5.5. The wash fastness of the fabric dyed at pH 3-5 ranged from very good to excellent.