| The in situ polymer method is adopted to prepare PA6/SiO2nanocomposites, in which nano-SiO2asfiller is added in the reaction system in the process of caprolactam polymerization. PA6/SiO2nanocomposite is prepared readily, with which the reactive nano-SiO2with amido functional groups is usedas filler, and nano-SiO2with different ratio of amido group and alkyl group, the effect of the functionalgroups on the surface of nano-SiO2on the properties of PA6are studied. Furthermore, the preparation ofPA6/SiO2nanocomposite is also prepared by combining masterbatch technique with in situ polymerization.PA6/Cu wire nanocomposite is also prepared by using copper nanowire as filler. Additionally, PA6/Cunanocomposite is skillfully prepared by using CuO as filler; CuO is reduced by only using the reducingatmosphere of reaction system. The effects of copper nanowire, nanocopper on the properties of PA6areresearched.The properties of reinforced PA6/SiO2nanocomposites by nano-SiO2with different functional groupsare analyzed in details. Findings show that the reactive nano-SiO2with amido groups is beneficial toremarkedly improve the mechanical properties of polyamide6due to the strong interfacial effect betweennano-SiO2and polyamide6matrix. However, the dispersible nano-SiO2with alkyl groups as filler is veryslight to enhance the mechanical properties of matrix, there is a major reason that the alkyl groups on thesurface of nano-SiO2can’t participate in the polymerization process of polyamide6thereby not formingchemically bonding with matrix and strong interfacial effect only forming physical adsorption effect.Additionally, nano-SiO2in situ-modified by different ratio of two silane coupling agents, which containamido functional groups and alkyl groups, respectively, is used as filler to improve the properties ofpolyamide6matrix. As-obtained results indicate that the mechanical strength gradually increase withenhancing the ratio of silane coupling agent with amido groups. Obviously, nano-SiO2in situ-modified bydifferent ratio of two silane coupling agents has different effect on the mechanical properties of polyamide6matrix. The major reason contains that the amido groups on the surface of nano-SiO2can participate in the process of caprolactam polymerization and form chemical bonding effect with the carboxyl end groupof polyamide6molecular chains, thereby forming a flexible interface layer on the surface of nano-SiO2thatincreases the interfacial strength of nano-SiO2and polyamide6matrix. However, the reducing ratio ofamido groups and alkyl groups on surface of nano-SiO2leads to slight interaction between nano-SiO2andpolyamide6matrix by only few hydrogen bonding and entangled chain segments, thereby reducing thetensile strength and modulus of elasticity.In order to improve the dispersion of nano-SiO2inside polyamide6matrix and reduce the powder dustpollution in the process of preparation of PA6/SiO2nanocomposites, we produce reactive nano SiO2masterbatch with20%concentration. As-prepared reactive masterbatch can be used as filler to preparepolymer-based nanocomposites by in situ polymerization and melt blending method. In this charcter,PA6/SiO2nanocomposites prepared by in situ polymerization via reactive nano-SiO2masterbatch as fillerare studied. This method by combining the masterbatch and in situ technology achieve the seconddispersion of nano-SiO2inside caprolactam monomer. Moreover, the reactive groups of nano-SiO2masterbatch can continually participate in the process of caprolactam monomer to form strong chemicalbonding with polyamide6matrix and strong interfacial interaction on the surface of nano-SiO2, therebyleads to the improvement of mechanical properties. The results arised from the curves of thermal lossweight also indicate an interesting phenomenon that the thermal loss weight percentage of nano-SiO2extracted from PA6/SiO2nanocomposites is obviously higher than that from masterbatch. Furthermore, themolecular chains of polyamide6on the surface of nano-SiO2can continually increase in the process ofcaprolactam polymerization. TEM photo of extracted nano-SiO2shows that a layer polyamide6molecularchains anchors on the surface of nano-SiO2thereby leading to the improvement of mechanical properties ofpolyamide6and the reducing crystalline temperature and completeness of crystalline size.The other properties of polyamide6, such as antifriction, antiwear, and antistatic properties, are alsodeveloped by using copper nanowire as filler via in situ polymerization. There is mainly because thatcopper nanowire possesses the high aspect ratio, good friction behaviors, and conductive properties. Theproperties of as-fabricated PA6/Cu wire nanocomposites with copper nanowire as filler, such as mechanicalproperties, friction and wear properties, crystalline and melting behaviors, thermal stability performance,are evaluated. The results show that tensile strength, impact stoughness, antifriction and antiwear of PA6/Cu wire nanocomposites are super to that of pure polyamide6. Copper nanowires separately disperseinside polyamide6matrix, as observed thin piece of PA6/Cu wire nanocomposites. It is beneficial to avoidthe aggregation of copper nanowire by in situ polymerization to prepare PA6/Cu wire nanocomposites.Moreover, the reducing atmosphere keeps the pristine state of copper nanowire thereby avoiding theoxidation of copper nanowire at high temperature. At the same time, copper nanowires also affect thethermal properties of polyamide6by results analysis of thermal gravimetric and differential scanningcalorimetry. The decomposition temperature, crystallization rate of PA6/Cu wire nanocomposites decreased,and the crystal structure tends to form crystal γ type in comparision with the crystalline type of purepolyamide6. There is mainly because that copper nanowires hinder molecular chain segment movement inpolyamide6matrix material thereby leading to forming the imperfect crystallization.Polyamide6/Cu nanocomposites with4-5-nm-diameter copper nanoparticles are readily prepared byskillfully combining the in situ reduction of cupric oxide and in situ polymerization of polyamide6. Theingenuity of as-involved method is to make useful of reductive atmosphere of the polymerization ofpolyamide6. Moreover, the uniform dispersion of as-obtained copper nanoparticles inside polyamide6matrix is achieved well, furthermore, the oxidation of copper nanoparticles is easily solved and coppernanoparticles keep prinstle state for long time due to the hindering effect of polyamide6matrix toatmosphere and steam. The analysis results of the properties of PA6/Cu nanocomposites show that thecontribution of copper nanoparticles on the improvement of mechanical properties of polyamide6is veryslight. Moreover, mechanical properties gradually decrease with increasing the content of cupric oxide. Thereduction of the molecular weight of polyamide6matrix is the main reason. There is because that the endamido groups of polyamide6are oxided for oxime in the reduction process of cupric oxide therebyhindering the continual growth of molecular chains of polyamide6. However, the antifriction, antiwear, andantistatic properties of PA6/Cu nanocomposites are remarkedly improved in comparision with that of purepolyamide6. Particularly, the resistance of PA6/Cu nanocomposites with0.5%cupric oxide contentreduces to108from1014of pure polyamide6. In order to keep the super friction and wear properties,antistatic performance of PA6/Cu nanocomposites, moreover, the mechanical properties is also reduced.The reduction agents are introduced into the reaction system of the preparation process of PA6/Cunanocomposites. The main reason is to avoid consuming the end amido groups of polyamide6for the reduction of cupric oxide, thereby reducing the effect of molecular chains of polyamide6. |
