Preparation And Characterization Of Nylon66/montmorillonite Nanocomposites By In Situ Polymerization

Nylon 66 has got widely used in the field of engineering plastics and fibers with excellent performance since its industrialization,its production and demand has been growing steadily. As the world's economic development,many application fields proposed higher and update requirements for materials,and as well as competition with other engineering plastics in cost-effective,the development of modified nylon 66 become a trend in full swing.Inorganic filler filled nylon 66 modified as a mature and effective means beared the encouraging development prospects.Preparing nano-composites by adding montmorillonite(MMT) into polymer matrix,which can increase the physical and mechanical properties of materials with a low MMT content,has attracted much attention in recent years.Polymer/MMT nano-composite materials is the main method of intercalation compound at present,in accordance with the composite process,the method can be divided into two types, intercalation polymerization and polymer intercalation,in this paper nylon 66 was selected as matrix,modifed the MMT by many methods,and prepare the nylon 66/MMT nano-composite by melt blending and in situ polymerization.Properties including mechanical, dynamic mechanical,flame-retardant,barrier,melting and crystallization behaviors,crystal morphology,thermal degradation behavior of nylon 66/MMT composites were studied.The main results as followed:1.Different OMMT have been prepared by modifying MMT with CTAB and silane coupling agent.TG,IR and XRD results showed that,=the thermal decomposition temperature and interlayer spacing of these OMMT were increased comparing with Na-MMT,which fit for the procession of nylon 66.2.A series of nylon66/MMT composite were prepared by melt blending,in situ polymerization and solution blending.The results of physical mechanical properties showed that the tensile strength and flexural strength of the composites increased by the largest 20%and 19%and the impact strength remained when the content of MMT is 2wt%.DMA analysis showed that the storage modulus of nylon66/MMT composites was improved by the addition of MMT, and increases as MMT contend increasing at the same temperature while the loss tanδdeclined.The main transition peak towards the high temperature,the glass transition temperature has increased 4～5℃.3.With the increasing of the MMT,the char yield and the heat decomposition temperature,heat distortion temperature were improved,the flame retardant and heat stability were strengthened.The rate of water absorption and water vapor permeability of composites declined with the increasing of MMT,the barrier property was improved.4.DSC results illuminated that there were two melting peak in the second melting curves of nylon66/MMT composites,the melting temperature was improved as MMT content increasing;The MMT plays a role of heterogenous nucleation in the process of crystallization, the crystallizing temperature,melting enthalpy,crystallinity were=increased and the width of half height declined,the total crystallization rate increased.PLM photographs revealed that MMT plays a role of nucleating agent,the radius of spherulites become smaller.5.The XRD results showed that the layer spacing of MMT become larger in the nylon66/MMT composites and well-distributed on the nanoscale in nylon66 matrix;the MMT aslo had the significant effect on the direction of crystal growth,grain size and crystallinity.6.SEM observation showed that the fracture mode of composites from ductile fracture to brittle fracture with the addition of MMT content;TEM and AFM photos showed that MMT particles were exfoliated into nanoscale lamellars and evenly dispersed in the nylon66 matrix, the lamellars lined on a certain degree of order,at last the exfoliated composite formed.