Preparation, Characterization And Properties Of Nylon 6 11 /Montmorillonite Nanocomposites

Polymer/montmorillonite (MMT) nanocomposites usually combine the advantages of the polymer materials and the inorganic materials. But it is not merely the simple adducts of their properties. The nanocomposites exhibited more excellent mechanical properties, thermal properties, improved barrier properties, superior flame-retardancy and reduced cost. In spite of great progress of nylon/MMT nanocomposites has been made in the past 20 years, there are still some deficiencies to overcome. First of all, only few kinds of nylon were adopted in the nylon/MMT nanocomposites. That is, many detailed investigations have been focused on the nylon 6/clay hybrids, while rather sparse kind of nylon-based nanocomposites were reported. Secondly, the research objectives were limited to the preparation and characterization as well as the macroscopical properties of nanocomposites. Nylon 11 is a kind of polymer matrix with high performances and is widely used in industrial fields from automotive to offshore oilfield applications. However, the yield cost of nylon 11 resin is relatively expensive. Moreover, the performance of the neat nylon 11 can not meet with requisitions for the development of hi-technology. To overcome these inherent shortages of nylon 11, we developed a new kind of nylon 6 11/MMT nanocomposite. In the present investigation, 11-amino-undecanoic acid, nylon 6 prepolymer and montmorillonite, which modified by 11-amino-undecanoic acid, were used to prepare nylon 6 11/MMT nanocomposite by in stiu polymerization. Our major research works were listed as following:(1) Preparation and characterization of nylon 6 11/MMT nanocompositesIn the presence of water, nylon 6 prepolymer was prepared through hydrolytic-polymeric reaction. Then nylon 6 11/ montmorilonite nanocomposite was prepared by in situ polymerization of 11-aminoundecanoic acid and pre-polyamide 6 in presence of organic-modified montmorilonite. The nylon 6 11 and nanocomposite were characterized by Fourier transform IR (FT-IR) spectroscopy; The morphological structure of nanocomposites was characterized by wide angle X-ray diffraction(WAXD) and scanned electron microscope (SEM); Differential scanning calorimetry(DSC) and thermal gravity(TG) were adopted to study the thermal properties; The mechanical properties, water absorption and oil absorption were investigated as well. These experimental results showed that in situ polymerization is suitable for preparation of nylon 6 11/MMT nanocomposites. In comparison with the neat nylon 11, both the mechanical and barrier properties of the nanocomposite were improved. Water absorption and oil absorption decreased 2 and 2.5 times.2. Investigation on the rheological behaviors of nylon 6 11/montmorillonite nanocompositesThe experimental results showed that both nylon 6 11 and nylon 6 11/montmorilonite were pseudoplastic and exhibited shear-thinning behavior. At a constant shearing rate, there was a similar influence of montmorilonite loading on the shearing stress and apparent viscosity. The reduction of the viscous activation energy with the increment of shearing stress indicated that nanocomposites can be processed over a wider temperature at a constant shearing stress.3. Investigation on the melt behaviors and crystallization of nylon 6 11/montmorillonite nanocompositesIt is found that although montmorillonite acts as the nucleating agent of the nylon 11 in our systems, it does not change the crystalline forms of nylon 11 matrix, which is different with nylon 6/ montmorillonite nanocomposites reported in literatures. And the melt behaviors and crystallization behaviors of nanocomposites were also investigated. The crystallization kinetics of nylon 6 11 and its nanocomposites were analysized using the classical crystallization kinetics equation. It was demonstrated that the Avrami equation was suitable to describe the isothermal crystallization of nylon 6 11 and its nanocomposites,while both the Avrami equation modified by Jeziorny and Mo's method described well the nonisothermal crystallization kinetics. Some important parameters for the crystallization kinetics were obtained. Additionally, the equilibrium melting temperature and the activation energy of nonisothermal crystallization for nanocomposites were calculated from Hoffman-Weeks equation and Hoffmann-Lauritzen theory.