Preparation And Characterization Of Fumed Silica/MCPA6via In-situ Anionic Polymerization

In the study reported in this paper, three initiator/activator systems, sodium ethanol/2,4-Diisocyanatotoluene (TDI), NaOH/N-acetyl caprolactam, and sodium ethoxide/N-acetylcaprolactam were used to prepare Monomer Casting polyamide6(MCPA6) and the influence ofthe polymerization conditions on the structure and properties of MCPA6were studied. The fumedsilica/MCPA6polymers were prepared via in-situ anionic polymerization and the products’structure and properties were characterized using various techniques including, Field EmissionScanning Electron Microscopy (FE-SEM), Thermal Gravimetric Analysis (TGA), DifferentialScanning Calorimetry (DSC), Wide-Angle X-ray Diffraction (WXRD) and tensile and impact tests.The primary results and conclusions of this study are:(1) Using orthogonal experimentation, the effect of the MCPA6polymerization parameterssuch as activator and initiatorcontent, mold preheating temperature, and heat preservation time ofmold, and dehydration temperature were examined and the influence of the activator content onthe structure and properties of MCPA6was further investigated. These experiments revealed thatthe optimum activator mole ratios of sodium ethanol/TDI, NaOH/N-acetyl caprolactam, andsodium ethoxide/N-acetyl caprolactam systems were0.25%,0.2%and0.2%, respectively.(2) The MCPA6and the fumed silica/MCPA6products prepared using the sodiumethoxide/TDI system were examined. The characterization test results suggested that the thermalstability of MCPA6was improved by the introduction of fumed silica, while theγ-crystallinecontent of MCPA6was increased. In general, the mechanical properties of fumed silica/MCPA6was somewhat enhanced.(3) The test results for the MCPA6and the fumed silica/MCPA6products prepared usingNaOH/N-acetyl caprolactam showed that the thermal stability and the crystallization of MCPA6were improved by the introduction of fumed silica. In addition, the γ-crystalline content wasincreased when the fumed silica content was0.5wt%and the tensile strength and impact strengthof fumed silica/MCPA6increased by10.2%and80.95%, respectively.(4) The properties of the MCPA6and the fumed silica/MCPA6products prepared using the sodium ethoxide/N-acetyl caprolactam system were also investigated. Introduction of fumed silicainto the MCPA6improved the material’s thermal stability and its α-crystalline content waspromoted by small quantities of fumed silica. The tensile strength and impact strength of thefumed silica/MCPA6with a1.0wt%fumed silica load increased by12.53%and95.89%,respectively. When the amount of fumed silica was greater than1.5wt%, the formation of aγ-crystalline phase was enhanced while the crystallinity decreased and water absorption capacityincreased.(5) The thermal degradation kinetics and non-isothermal crystallization kinetics of theMCPA6and fumed silica/MCPA6products prepared using sodium ethoxide/N-acetyl caprolactamwere investigated using both TGA and DSC. The experimental results showed that the thermaldegradation activation energy of the fumed silica/MCPA6material was higher than the MCPA6and was enhanced by the increase of conversion rate. The effective energy barrier fornon-isothermal crystallization of fumed silica/MCPA6was higher than the MCPA6and increasedwith increasing fumed silica content. The Mo model clearly described the non-isothermalcrystallization process of this sodium ethoxide/N-acetyl caprolactam system.