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A simple, green, and scalable procedure to manufacture spherical lignin nanoparticles is demonstrated in this work. Softwood kraft lignin (S-lignin) was fractionated using acetone which was recoverable and reused in the following step to produce lignin nanoparticles (S-LNPs). Deionized water was used as anti-solvent to precipitate S-LNPs under ultrasonication. The size of S-LNPs was found to be in the range from 40-300 nm with an average of 120±18 nm. S-LNPs had lower ash content at 0.05% as compared to 1.22% of S-lignin. More importantly, S-LNPs had significant increased phenolic to aliphatic hydroxyl ratio. Home-composable polybutylene succinate (PBS) was selected to develop sustainable materials for flexible film applications. Composite films of PBS/S-lignin and PBS/S-LNPs were manufactured via conventional blown film melt-extrusion. Both composite films appeared brownish. At 0.5 wt% loading content, the PBS/S-LNPs composite films possessed comparable mechanical properties to the neat PBS film with several advantages including (a) a superb UV-blocking ability of 69% and 64% enhancement in shielding of UV-B and UV-A, respectively; (b) retardation of thermo-oxidative reaction with 42 % improvement in onset oxidative temperature; and (c) antibacterial activity (R) values of 2.5 for gram-negative (E. coli ATCC8739) and 1.5 for gram-positive (S. aureus ATCC 6538p). For a meaningful approach in fully biodegradable and sustainable plastic products, the spherical lignin nanoparticles produced in this work can be alternative multifunctional bio-additives for UV protection, antioxidation and antibacterial applications.

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.

Honeycomb structures of TiO2-modified hydroxyapatite composite (HA/TiO2) were fabricated using extrusion technique. The mixture formulations of HA/TiO2 extrusion pastes (S1-S4) were investigated to optimize the process. The filtering effectiveness of the HA/TiO2 honeycombs was evaluated by photocatalytic activity measurement and a bactericidal test. The effects of sintering temperature and honeycomb thickness on photocatalytic and antibacterial activities were additionally studied. The S3 and S4 honeycomb samples, sintered at 650°C, exhibited a similar trend in reducing methylene blue concentration. At 800°C, the S3 honeycomb sample showed a slightly faster reduction in methylene blue concentration compared to the S4 honeycomb. Honeycomb samples of 2 and 5 cm in thickness showed significantly greater photocatalytic activity than that of 1 cm such that methylene blue concentrations rapidly decreased after UV exposure for 24 hours. The S3 and S4 honeycomb samples also exhibited decomposition of both gram-negative E. coli and gram-positive S. aureus. Approximately 50% of gram-positive S. aureus and gramnegative E. coli were decomposed by the honeycombs in the sample-thickness dependent manner after 2 hours of UV exposure. Low survival ratios of bacteria (5% - 10%) were observed after 6 hours of UV exposure and the 2 mm and 5 mm thick honeycomb samples showed the greatest and most similar antibacterial activities.