Preparation, Structure And Properties Of Nylon 6/Elastomer/MMT Ternary Composties

In this article, nylon(PA6), nano-montmorillonite(MMT), EPDM and EPDM-g-MAHhad been used to prepare PA6/elastomer/MMT nanocomposties by melt-blending,EPDM-g-MAH/EPDM and nanomontmorillonite were used as the impact modifier for thenylon 6. The relationship between the structure and properties of nylon 6 toughened andreinforced by montmorillonite,EPDM-g-MAH/EPDM respectively or together was studiedsystematically. Deep investigation and analysis on high performance and theory of nylon 6was carried out. These information can be used for development and application the nyloncomposites with high properties. Besides study on mechanical properties, we investigated itsrheological behavior, melt and crystallization behavior. The main results are listed asfollowing:1. Preparation and characterization of PA6/MMT/elastomer nanocomposites:Nylon 6/MMT/elastomer nanocomposites were prepared by melt intercalation. Themorphological structure of nanocomposites was characterize by wide angle X-ray diffraction(WAXD) and scanned electron microscope(SEM), the results show that, the intercalatednanocomposites were obtained when the montmorillonite content was 2% while the exfoliatednanocomposites were obtained when the montmorillonite content was 5%;The effect of adding montmorillonite content less than 5% on the diameter distributionwas small, the diameter of elastomer particle was small. With the montmorillonite contentmore than 5%,MMT layers distributes elastomer, forming nuclear shell structure, the diameterof elastomer particle and modulus increased, so that the impact strength decreased. With theincrease of elastomer content, the diameter of elastomer particle decreased at first and with aminimum when the elastomer content was 20%, the diameter of elastomer particle increasedwith the elastomer content was 25%. The critical layer thickness of brittle-tough transition fornano-composites was 0.22μm.The experimental results demonstrated that:the impact strength of the nylon 6/MMT/elastomer nanocomposites increased at first then decreased with the increase of the elastomercontent. When the elastomer content was 20%, the impact strength for the nanocompositeswas 54.29KJ/m~2 which was 10.24 times as much as the impact strength of 5.29KJ/m~2 for nylon 6/MMT nanocomposites. The tensile strength and flexural strength decreased graduallywith the increase of elastomer content. However, the breaking elongation ration increased atfirst then decreased with the increase of the elastomer content and was up to the max when theelastomer content was 20%. the impact strength of the nanocomposites increased at first thendecreased with the increase of the MMT content, When the MMT content was 2%, the impactstrength for the nanocomposites was 54.29KJ/m~2 which was 12.08 times as much as theimpact strength of 4.15KJ/m~2 for pure nylon 6. The tensile strength, flexural strength andflexural modulus decreased gradually with the increase of MMT content. However, thebreaking elongation ration increased at first then decreased with the increase of the MMTcontent and was up to the max when the MMT content was 2%.2. Investigation on the rheological behaviors of Nylon 6/MMT/elastomer nanocomposites:The experimental results showed that both PA6 and Nylon 6/MMT/elastomernanocomposites were pseudoplastic and exhibited shear-thinning behavior. the viscosity of thePA6/EPDM/MMT ternary nanocomposites melts first increases and then decreases, whoseturning point moves forward with the increase of temperature, the apparent viscosity of theblends increased at first and then decreased ,and the apparent viscosity reached maximumvalue when the content of elastomers was 20%; Different from the influence on rheologicalproperties of the PA6 matrix composites of the ordinary inorganic packing, the addition of theEPDM limits the internal plasticization of montmorillonite."Layered sponge - stacked silk " model is first built to explain the effect of organic layersilicate mineral content on the melt viscosity of polymer/layered silicate composite materials.MMT layers distributes first among random macromolecular chains (like sponges), restrictingthe procedure of unfastening. But when MMT content increases to a certain degree filling thegaps among winding chains (sponges), the MMT begins to distribute among themacromolecular chains of orientation (like silks), weakening the wind of macromolecularchains and sliding with the macromolecular chains of orientation acting as Inside plasticizer.The bigger is shear stress or the higher is the temperature, the more are the macromolecularchains of orientation (like silks) and the less are random macromolecular chains (likesponges).3. Investigation on the melt and crystallization behaviors of Nylon 6/MMT/elastomernanocomposites:It is found that although MMT acts as the nucleating agent of the PA6 in the systems, it changes theγcrystalline form toαform of PA6 matrix. The melt and crystallization behaviorsof nanocomposites were also investigated, and calculated its equilibrium melting temperature.The crystallization kinetics of PA6 and its nanocomposites were analysized using the classicalcrystallization kinetics equation. It was demonstrated the Avrami equation was suitable todescribe the isothermal crystallization of PA6 and its nanocomposites. The Ozawa equationand the Avrami equation modified by Jeziorny were not suitable to described thenonisothermal crystallization kinetics, but the Mo's metheod described well. Some importantparameters for the crystallization kinetics were obtained. Additionally, the activation energyof nonisothermal crystallization for nanocompotites were calculated from Hoffmann-Lauritzen theory.