| Nylon 6 is used in a wide range of engineering applications because of it s unique mechanical properties and processability, Various reinforcements , such as glass, carbon, and natural fibers and whiskers, are often added to further upgrade the performance of nylon 6. It was expected that the mechanical properties would be further increased, if additives were dispersed in nylon 6 matrix in the dimension of nanometer. The preparation of nylon 6 nanocomposites with silicate reinforcements via either in situ polymerization or melt exfoliation has attracted increasing attention recently. This material exhibits excellent mechanical characteristics and gas –barrier properties because of the nanoscale dispersion of clay reinforcements in polymer matrix. Although many of the property enhancements seen in nylon6 nanocomposites may be explained by the intercalation and dispersion of high modulus, high aspect ratio silicate layers in a relatively low modulus matrix, some property effects may be related to structural modification of the polymer matrix. Therefore, it is important to understand, especially from a design standpoint, what factors influence the formation or enhancement of the crystalline forms of nylon 6 and how physical and mechanical properties may be affected. In this study, we studied the crystalline structure, thermal and mechanical properties by changing the surface properties of montmorillonites. Structural characterizations were carried out with different techniques.Preparation of nylon 6/montmorillonite nanocomposite: In a 800 ml beaker were placed 4.8 g 11- amino acid , 2.4 ml of concentrated sulfuric acid, and water solution containing 20 g montmorillonite at 80 oC. The mixture was stirred vigorously for 3 hours and then cooled to room temperature. The product was filtered, washed three times with 1000 ml of hot water, dried in vacuum at 100 oC, The ion-exchanged montmorillonite obtained by this process will be termed as treated montmorillonite. The treated montmorillonites with different weight and caprolactam were mixed in a mortar. The mixtures were heated to the ring-opening polymerization caprolactam, using 6-aminocaproic acid as the initiator under nitrogen atmosphere. X-ray and transmission electron microscopy studies show that the silicate layers of montmorillonite were uniformly dispersed in nylon 6 matrix and to form organic-inorganic nanocomposiye.Morphology of nylon 6/montmorillonite nanocomposite: When natural and treated montmorillonite were added to nylon 6 matrix by in-situ polymerization, the basal spacings of two kinds of montmorillonites increased. The increased distance is in inverse proportion to the content of montmorillonite in nylon 6 matrix.Crystallization behavior of nylon 6 nanocomposite: Nylon 6 exhibits two ( crystalline peaks. However, the addition of montmorillonite changed the crystal structure of the nylon 6 matrix. A new crystalline peak was investigated at 2θ = 21.7 o in diffraction pattern of nylon 6 nanocomposite, which attributed to the ( crystalline phase of nylon 6. Generally, the ( - crystalline phase is unstable in nylon 6 and appears in the quenched nylon 6. It is obvious that the silicate layers of montmorillonite favor the formation of the ( - phase. DSC scan of nylon 6 has a single melting peak while that of nylon 6 nanocomposite has two peaks. This regularity is corresponding to the X-ray result. The addition of montmorillonite restricts the spherulitic growth of nylon 6 and destroys spherulitic structure. 11-amino acid treated montmorillonite has stronger chemical interaction with nylon 6 molecules, and play the roles of nucleating agent, which has been proved by Malau test and IR spectra.4.Mechanical properties of manocomposite: Nylon6/montmori-llonite nanocomposite was found superior in tensile strength, modulus, elongation at break and impact strength at lower montmorillonite content compared with nylon 6. The mechanical properties nylon 6/ treated montmorillonite nanocomposite are more excellent than...
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