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Sound absorption performance of needle-punched nonwovens containing polyester fibers of different sizes (7 and 15 denier) and configurations (hollow, 4-hole, hollow conjugated, and hollow trilobal), as well as their composites with perforated rubber layer were investigated. From results, nonwovens of finer 7-denier fibers exhibited higher sound absorption coefficient (α) than that of coarser 15-denier fibers. This was due to greater amount of fibers in nonwovens and larger fiber surface area, thus longer tortuous path for sound waves to travel. Nonwoven of 4-hole fibers (7-4H) showed higher sound absorption performance than that of single hole fibers (7-H) due to increase in surface areas of small holes inside the fibers, thus increasing tortuous path. Likewise, increase in hollow area in the hollow conjugated fibers (15-HC), and angular configuration in the hollow triangular fibers (15-HT) resulted in greater sound absorption coefficient, compared to those of hollow fiber counterpart (15-H). Increasing nonwoven layer to 2 and 3 layers yielded an increase in sound absorption coefficient due to greater thickness and more air gaps between the nonwoven layer. The rubber/nonwoven composites, where perforated rubber layer was inserted between nonwoven layers, exhibited higher sound absorption coefficient in a low-frequency range. This study demonstrated that sound absorption performance could be enhanced through a wide frequency range by employing nonwoven of fine fibers having irregular shapes and large hole area, in combination with perforated elastic rubber.

Tetraphenyl phosphonium-modified organoclay (TPP-Mt) was prepared by modifying montmorillonite-rich Thai bentonite via ion exchange. TGA results revealed that TPP-Mt possessed high thermal stability, where degradation occurred at a temperature range of 418-576°C. The obtained TPP-Mt/PP nanocomposites exhibited degradation at higher temperatures than PP (410-420°C vs. 403°C). Fibers of different cross-sectional shapes (circular, circular hollow, and cross) containing 1, 2 and 3%wt TPP-Mt were prepared and characterized. Nonwovens of 3%wt TPPMt/PP fibers were fabricated for flame retardant test. From results, nonwovens of TPP-Mt/PP fibers exhibited self-extinguishing characteristic and the areas of burning were less than that of PP nonwoven (14.5-31.6% vs. 95.6%). Nonwovens of cross-shaped fibers showed the best flame retardant property, followed by those of circular hollow and circular fibers. The flame retardant properties observed in nonwovens were explained due to the inter-fiber spaces between cross-shaped fibers and center hole in circular hollow fibers, which could trap initiating radicals inside, thus reducing flame propagation. In addition, large surface area in cross-shaped fibers could help in increasing the flame retardant effectiveness due to more exposure of TPP-Mt particles to the flame. Knowledge obtained in this study offered an approach to produce flame retardant nonwovens via a combination of modified organolcay and fiber shape.

Melt spinning of 50/50 hollow segmented-pie bicomponent fibers, each containing a pair of either poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) or PLA and polypropylene (PP), was conducted to investigate effects of constituent polymers on arrangement and properties of the obtained fibers. PLA/PBS fibers exhibited flat interfaces between PLA and PBS segments, while PLA/PP fibers exhibited curved interfaces having concave-shaped PLA segments and convex-shaped PP segments. The curvature at interfaces was due to the molten low-viscosity PLA encapsulating the high-viscosity PP. The results showed that fiber splitting was complex, and its mechanism depended not only on the properties of each polymer constituent but also interactions between them. PLA/PP fibers exhibited the tendency of fiber splitting due to the incompatibility between PLA and PP as well as an imbalance force at the interface. In PLA/PBS fibers, the fiber splitting was not observed. The balance force of flat interface between PLA and PBS could contribute to the reduction of interfacial tension. In addition, small domain size in a range of 3–5 µm could favor compatibility between the PLA and PBS segments. Observations from this study suggested a possibility of employing segmented-pie configuration as an alternative approach for developing PLA/PBS fibers of high PBS content without phase separation.

Antibacterial polypropylene cross-sectional shape fibers were melt spun with adding nano ZnO and modified chitosan. Two types of fiber cross-section, round and worm cross-sectional shape were studied including with nano ZnO and modified chitosan loading. Antibacterial properties, surface area, and fiber crystalization were investigated. The surface area of the fiber and antibacterial properties were directly related to the cross-sectional shape. The greater antibacterial properties was found at lower modified chitosan loading compared ZnO.

The primary aim of this paper is to provide an insight on the effect of chitosan compounds on the properties of polypropylene/chitosan composite fiber prepared by melt spun process. Three types of chitosan powder including ball mill prepared chitosan, spray dry prepared chitosan, and soybean oil-g-chitosan were employed for the preparation of chitosan compounds using polypropylene as polymer matrix. Then, chitosan compounds were incorporated into polypropylene fibers by melt spinning process. Polypropylene fibers containing chitosan particle loadings of 0.5 wt%, 1 wt%, and 3 wt% were prepared. Tensile strength, thermal property, morphology of chitosan compounds and fibers were investigated. The soybean oil-g-chitosan particles were found well distributed in PP matrix due to the compatibility of hydrophobic interfaces. However, spray dry-chitosan exhibited the best reinforcement effect by imparting the highest toughness compared to the others.

Novel organic luminescent substance (3,12-bis(dibutylamine)-7,8-dicyano-5,6,9,10-tetrahydro[5]helicene; M123) was successfully synthesized and employed to prepare luminescent polypropylene (PP/M123) fibers of different cross-sectional shapes via melt spinning. For all cross-sectional shapes (circular, hollow triangular, flat, star, and W), the PP/M123 fibers were continuously spun without fiber breakage, and possessed smooth surfaces. The designed structure of M123, containing 4 butyl groups, enabled its homogeneous mixing with hydrophobic polypropylene matrix. Addition of M123 did not alter the PP melt flow through complex spinneret orifices during fiber spinning, as evidenced by rheological measurements that melt viscosities of PP and PP/M123 at different shear rates (10–10,000 s−1) were almost identical. Results from differential scanning calorimetry also confirmed homogeneity of M123 and PP matrix as the melting temperatures and crystallinities of PP/M123 fibers were comparable to those of PP fibers. By employing organic luminescent M123, the processes of additive preparation and additive/polymer compounding were simplified, and small amount of luminescent substance as 0.05 % wt. could be used to yield effective luminescence. The PP/M123 fibers exhibited yellowish green color under normal light and emitted bright green light under ultraviolet (UV) light.

1, 25, Journal of Metals, Materials and Minerals

Melt spinning of cross-shaped polypropylene (PP) and poly (lactic acid) (PLA) fibers was conducted to investigate influences of polymer properties and processing conditions on cross-sectional shape change in fibers. PP fibers possessed cross-shaped profile, resembling that of the original spinneret orifice, with dull edges due to die swell. Their shape factor (SF) values (1.4–1.6) were close to that of the spinneret orifice (1.7), indicating that the complex shape of the orifice could be maintained. High melt viscosity of PP, as well as its rapid crystallization, helped preventing shape change induced by surface tension. PLA fibers, on the other hand, exhibited shape change from cross to square and to round shape when spinning temperature was increased from 200 to 220 and 240 °C, respectively. Their SF values (1.1–1.2) were close to unity, indicating shape change towards circular shape. Shape deviation towards circular shape in PLA fibers was mainly driven by surface tension. Slow crystallization in PLA allowed great influence of surface tension in determining shape change of the extrudate. Increasing fiber take up speed tended to decrease SF value. Such effect was small compared to that of spinning temperature.