Lithium-sulfur (Li-S) batteries are being considered as one of the most promising candidates for the development of next-generation energy storage technologies. Although much progress has been made over the past decade, the development of Li-S batteries is still scourged by a crucial polysulfideshuttle problem. To address such a critical issue, we present here an approach to reduce the pore size of the separator to prevent the penetration of soluble polysulfide species. A polymer with intrinsic nanoporosity (PIN) is developed within the micron-scale pores of a polypropylene separator. The framework of polypropylene acts as a skeleton to sustain reliable mechanical properties with the thin membrane. Upon the formation of PIN in the pores, the polypropylene separator maintains its thickness. With the thin PIN-polypropylene membrane, the Li-S cells could be operated with relatively high sulfur loading. The PIN allows the transport of Li +-ions, but suppresses the penetration of the polysulfide species. The Li-S batteries with the PIN modified polypropylene separator exhibit enhanced cycling performance.
Antimicrobial polyamide 11 (PA-11) films containing low-cost, thermally stable and water resistant polymeric biocide polyhexamethylene guanidine dodecylbenzenesulfonate (PHMG-DBS) have been obtained by compression moulding. The structure of the modified PA-11 films containing from 3 to 10 wt% of PHMG-DBS was characterized using Raman and FTIR spectroscopy and atomic force microscopy (AFM). The surface properties were evaluated both by contact angle and contactless inductive method. The introduction of PHMG-DBS into PA-11 films was found to increase positive surface charge density to 5.5Á10 -11 C/cm 2 for 10 wt% of PHMG-DBS. Antibacterial activity of PA-11/ PHMG-DBS films against both Gram-positive (Escherichia coli) and Gram-negative (Bacillus subtilis) bacteria was demonstrated for films containing from 5 to 7 wt% of polymeric biocide. According to thermal investigations data, PA-11/ PHMG-DBS composite has excellent thermal stability to at least 390°C both in air and in argon atmosphere which indicates on its availability for the melt processing by common methods. It has also been found that polymeric biocide is highly resistant to leaching from PA-11 film.
Flame retardant polyamide 6 (nylon 6) nanocomposite nanofibers containing montmorillonite clay (MMT) platelets and intumescent non-halogenated flame retardant (FR) additives were processed by electrospinning. Different methods of mixing nano fillers before electrospinning were explored and compared. It was found that high loadings of nanoclay particles affected the electrospinnability of the nanocomposite material. Good dispersion and exfoliation of nanoclay platelets within individual nanofibers was verified by transmission electron microscopy. The degradation temperature of nanocomposite samples was lower than pristine nylon 6 samples. However the degradation of all nanocomposite formulations was overall slower. Moreover, the difference in residual char weight after decomposition was significant. Microscale combustion calorimeter results show that FR particles played a major role in reducing flammability of the material in both solution- and melt-compounded samples, while MMT nanoclay was effective in improving char residue and in reducing flammability in high-shear melt premixed samples.
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