Research On Preparation And Properties Of Toughened MCPA6

Monomer casting polyamide 6 is limited by notch sensitivity, weakness of impact toughness and high water absorption in application. To overcome these disadvantages, rubber elastomers, thermoplastic polymers and inorganic nanoparticles were generally introduced into the polymerization of caprolactam. However, rubber elastomers with high melt viscosity were not suit for MCPA6. Thermoplastic polymers could only play a significant effect on thoughening of PA6 at high content. The interface compatibility between inorganic nanoparticles and resin matrix was poor, resulting particles agglomeration easily. In the study, organic and inorganic components with reactive groups and special structure, namely, styrene-butadiene-glycidyl methacrylate copolymers(SBG), acrylonitrile-butadiene-styrene copolymer(ABS) with core-shell structure, and halloysite nanotube(HNT) were selected as modifying agent to prepare PA6/SBG, PA6/ABS and PA6/HNT composites via in situ anionic ring-opening polymerization of caprolactam. The compatibilizing effect of maleic anhydride grafted acrylonitrile-butadiene-styrene(ABS-g-MA) on the PA6/ABS blends was further investigated. The structure and properties of materials were investigated by all kinds of methods,e.g. Scanning Electron Microscopy(SEM), Differential Scanning Calorimetry(DSC), Wide-Angle X-ray Diffraction(WAXD), Thermal Gravimetric Analysis(TGA) and mechanical properties test. The main contents and conclusions of the research are as follows:(1) In the study of PA6/SBG, it was found that monomer conversion and water absorption decreased with the increasing content of SBG. A certain degree of compatibility was observed between PA6 and SBG as a result of the interaction of reactive functional groups. The notched impact strength and elongation at break of PA6/SBG increased as SBG content increasing, whereas the tensile strength decreased.(2) In the study of PA6/ABS, phase domain expansion and interfaces separation were obvious at high ABS content. The notched impact strength increased firstly and then decreased with the increasing amount of ABS, but the tensile strength decreased gradually. The interface compatibility of PA6 and ABS was enhanced by ABS-g-MA. Moreover, excessive ABS-g-MA played a role of macroactivator to initiate the polymerization of caprolactam. With the increasing ABS content, the water absorption decreased further. However, the tensile strength, elongation at break and notched impact strength increased gradually.(3) In the study of PA6/HNT, it was found that the interface performance of HNT and PA6 was improved by the silane coupling agent. The decreased monomer conversion and relative molecular weight, broaden molecular weight distribution and improved decomposition temperature were caused by the incorporation of HNT. The initiative decomposition temperature of PA6/HNT increased by 38.2 °C when 1.5 wt% HNT was added. With the increase of HNT content, the tensile strength and notched impact strength increased firstly and then decreased, whereas elongation at break decreased gradually. The method developed by Mo was successful in describing the nonisothermal crystallization of PA6 and PA6/HNT. The activation energy for PA6/HNT was higher than that of PA6.The study of different polymer systems revealed that ABS with low rubber content was more effective than SBG with high rubber content in improving the toughness of PA6 and minimising losses of tensile properties, because nitrile groups in ABS occurred alkaline hydrolysis reaction. ABS-g-MA showed obvious compatibilizing effect in PA6/ABS, thus tensile properties and impact property was enhanced. HNT had positive effect in improving the tensile strength, but the improvement of notched impact strength was less than ABS and SBG.