Preparation And Properties Of Nanometer Silver And Its Nylon 6 - Based Nanocomposites

Silver nanoparticles (AgNPs) and its nylon 6-based composites have attracted considerable attentions in academic and industrial fields because of their potential applications. In the present study, ε-caprolactam (CL) was used as a multifunctional reagent to be the roles of reducing agent, protecting agent and solvent in the synthesis of AgNPs, and be the monomer for the preparartion of AgNPs/PA6 composite through successive in-situ method. And AgNPs/PA6 composite microspheres were prepared when a polymerization induced phase seperation was introduced. What’s more, the evlution of AgNPs in molten CL was disclosed, and the growth of the PA6 microsphere was discussed and the influences posed by nanoparticles was studied. The whole works included:1. AgNPs was synthesized through the reduction between CL and silver nitrate (AgNO3). The reaction of CL with AgNO3 was analogous to the reaction of CL with oxygen. Basing on the previous studies, the reaction mechanism of CL with AgNO3 was proposed.2. The degree of ionization of AgNO3 in molten CL at 140℃ lower than l‰, which guranteed the reduction of AgNO3 with CL to be proceed moderately. The coordination of CL with Ag+ and Ag0 enable to produce prime small particles. The investigation showed that the growth of AgNPs experienced two different stages. At first, particles were stabilized against further condensation at a smaller size (<5 nm) because of face-binded CL. In the second stage, the Ostwald ripening mechanism cooperated with continuous surface reduction of residual Ag+, leading to the resultant particles with different size distribution and various shapes. The participation of CL in the reducing and protecting procedures raise a complex evolution of AgNPs, and then the morphology of resultant AgNPs.3. A novel approach to in situ synthesis of AgNPs/polyamide 6 (AgNPs/PA6) nanocomposites was presented. The method included two steps:in situ preparation of silver nanoparticles (AgNPs) in molten ε-caprolactam (CL), followed by polymerization of residual CL. The properties of AgNPs and resultant composites were explored.4. A novel approach to in situ synthesis of AgNPs/PA6 composites microsphere was presented. The molecular weigh of polystyrene (PS) and the mass loading of AgNPs significantly influenced the morphology of resultant AgNPs/PA6 composites microsphere. The lower molecular weigh PS was sensitive to the loading of AgNPs, and once it was increase to proper range, the resultant PA6 can be maintained the microsphere morphology when the silver loading was less than 1.5wt%. The properties of AgNPs/PA6 composite microsphere were explored.5. During the polymerization induced phase seperation, the concentration of PS and the initial polymer temperature influenced the phase reversation and final morphology. The lower concentration of PS producing less surface cann’t surround PA6 phase, and then generated no reversation of PA6 phase. The polymerization and crystallization of PA6 was proceeding simutaniliously, but their relative intensity can be adjusted by the initial polymerization temperature. And This will influence the mobility of the PA6 molecules, which then consequenced in the final morphology of PA6. Beside the mobility of PA6 molecules, the surface properties of nanoparticles loading in PA6 matrix siginificantly influenced the reaultant morphology. The TiO2 NPs that with big surface tension intented to form small separating cluster and then promoted the phase seperation in the polymerization. The SiO2 NPs that with small surface tension intented to self-agglomerate to form the network frame. The polymerization started from the network frame produced a cooresponding network PA6 frame, and polymerization that happened in other place generated the sphere-like PA6 domination. The coalesce from sphere PA6 domination to the network PA6 frame resulted in the bulk PA6 phase, and the whole precess was droven by the SiO2 NPs.