Silver Nanoparticles/Elastomer Composite Fibers Prepared By Electrospinning And In-Situ Chemically Crosslinking

The material processing technique of electrospinning provides a viable approach for convenient fabrication of fibers with diameters ranging from nanometers to microns. Polymers that have been electrospun into fibers are mostly thermoplastics; despite that there have been a few publications on electrospun fibers of rubbers, the fabrication of these fibers remains a technological challenge due to viscoelasticity of the materials at ambient temperature as well as formation mechanism of the rubber fibers during electrospinning. Rubber microfibers, including polybutadiene rubber (BR), butyl rubber (Ⅱ), and silicon rubber (SiR), with uniform diameter and morphological stability were prepared through combination of electrospinning and in-situ chemical crosslinking. The main researches were as follows.1.The effect of processing variables (voltage, syringe rate, the distance between the collector and needle) and internal factor (molecular weight, molecular weight distribution, viscosity, solution electrical conductivity) on the morphology of electrospun rubber microfibers were first systematically discussed. This study revealed that the formation of electrospun ruber fibers was correlated with the overlap/entanglement of rubber macromolecules in the spinning solutions; for the formation of uniform fibers without beads and/or beaded fibers, the concentration of spinning solution had to be higher than the 'critical chain entanglement concentration (Ce)' and the value of Ce divided by the value of C* appeared to be a constant of～2.8.2.Prior to electrospinning, camphorquinone (CQ) for BR andⅡR, while two-part platinum catalyst for addition curing of SiR, were added into the solutions for in-situ chemical crosslinking.The morphology and crosslinking density of electrospun rubber microfibers were investigated by optical microscope and NMR respectively. The CQ/BR and CQ/ⅡR mass ratio of 1/20 (TM-10B/SiR and PL-10A/SiR mass ratio of 6% and 4% respectively) was identified as the optimal based upon morphological properties of the resulting fibers. The study suggested that the in-situ chemical crosslinking was an effective method to substantially improve the morphological stability of electrospun fibers; upon prolonged storage under ambient condition or even upon immersion in THF (a good solvent for BR,ⅡR and SiR), the crosslinked BR, IIR and SiR fibers well-retained their morphology.3.In this study, Ag nanoparticles were first in-situ formed by reducing the Ag+ ions in rubber/DMF/THF solution under UV-irradiation, then elastomer composite fibers were made by electrospinning the above solution and in-situ shortly crosslinking the spun fibers at one time. As indicated from UV absorption spectroscopy, XPS and TEM results, Ag NPs with sizes of 10-20nm were uniformly dispersed in elastomer fibers. It was believed that besides the protection of PVP, a rapid solvent evaporation and limited motion space for a very fine fiber during electrospinning could obstruct the aggregation of the Ag NPs, resulting in a very homogenously dispersion. As expected, electrospun BR microfibers with Ag NPs showed very strong antimicrobial activity with very low loading amount of 3%～5% AgNO3. This kind of elastomer composite fibers with functionalities would be promising.