Abstract
Polymer components capable of self-healing can rapidly be manufactured by injecting the monomer (ε-caprolactam), activator and catalyst mixed with a small amount of magnetic nanoparticles into a steel mould. The anionic polymerisation of the monomer produces a polymer component capturing magnetic nanoparticles in a dispersed state. Any microcracks developed in this nanocomposite component can be healed by exposing it to an external alternating magnetic field. Due to the magnetocaloric effect, the nanoparticles locally melt the polymer in response to the magnetic field and fill the cracks, but the nanoparticles require establishing a network within the matrix of the polymer through effective dispersion for functional and uniform melting. The dispersed nanoparticles, however, affect the degree of crystallinity of the polymer depending on the radius of gyration of the polymer chain and the diameter of the magnetic nanoparticle agglomerates. The variation in the degree of crystallinity and crystallite size induced by nanoparticles can affect the melting temperature as well as its mechanical strength after testing for applications, such as stimuli-based self-healing. In the case of in situ synthesis of the polyamide-6 (PA6) magnetic nanocomposite (PMC), there is an opportunity to alter the degree of crystallinity and crystallite size by optimising the catalyst and activator concentration in the monomer. This optimisation method offers an opportunity to tune the crystallinity and, thus, the properties of PMC, which otherwise can be affected by the addition of nanoparticles. To study the effect of the concentration of the catalyst and activator on thermal properties, the degree of crystallinity and the crystallite size of the component (PMC), the ratio of activator and catalyst is varied during the anionic polymerisation of ε-caprolactam, but the concentration of Fe3O4 nanoparticles is kept constant at 1 wt%. Differential Scanning Calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), XRD (X-ray diffraction) and Thermogravimetric analysis (TGA) were used to find the required concentration of the activator and catalyst for optimum properties. It was observed that the sample with 30% N-acetyl caprolactam (NACL) (with 50% EtMgBr) among all of the samples was most suitable to Rapid Prototype the PMC dog-bone sample with the desired degree of crystallinity and required formability.
Highlights
The Differential Scanning Calorimetry (DSC) results were plotted for all samples with variations in the concentrations The results were plotted all samples with variations at in least the concentrations of of EtMgBr, N-acetyl caprolactam (NACL)
With the help of DSC plots, it could be deduced that considerable melting and annealing occurred prior to the final melting in all three variations ((EtMgBr, NACL and EtMgBr+ NACL) with proportions equal or higher than 50%
Samples with 10%, 30% and 100% EtMgBr and NACL concentrations were observed with much broader bands associated with the amide group compared to polymer nanocomposite (PMC) the samples produced by varying the catalyst and activator separately, indicating that the amorphous phase consisted of a wider distribution of the α-like and γ-like structures
Summary
Many nanoparticle dispersion techniques, such as melt blending, J. Many nanoparticle dispersion techniques, such as melt blending, solution blending,blending, high‐shear mixing and in situ polymerisation, have been have used been [3–8].used. PMC, PA6 as it in manufacturing situ PMC manufacturing method is mostfor favoured for PA6 preparing provides ease ofthe mixing nanoparticles in a low‐viscosity ε‐caprolactam monomer. PMC, as itthe provides ease the of mixing the nanoparticles in a low-viscosity ε-caprolactam before the before activator/catalyst‐mediated polymerisation [9] is carried[9]. Out, ensuring effective monomer the activator/catalyst-mediated polymerisation is carried out, ensuring effectiveThe dispersion. Due to interface and MNPs dispersion, dispersion, thecrystallinity degree of crystallinity and thestructure crystalline structure within the the degree of and the crystalline within the polymer arepolymer affected are affected which, in turn, the multifunctional of the synthesised [3,4], which,[3,4], in turn, affects the affects multifunctional propertiesproperties of the synthesised polymer polymer
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