Most of the anicles on polymer nanocomposites focus on the importance of chemistry used to modify the surfaceof the clay

usually montmorillonite (MMT)

and characterization of the nano-scale structure obtained. The role andimportance of processing were also discussed recently. However

few papers concerning the correlation between morphologyof MMT and mechanical properties were published. In order to understand the tensile behavior of PP/Montmorillonite(MMT) nanocomposites better

and to further improve the reinforcement efficiency

we first prepared the PP nanocomposites via direct melt intercalation using conventional twin-screw extrusion.The dispersion and tensile property of the composites were then investigated by SEM

XRD

TEM and a video-controlled tensile set-up.The macroscopic and microscopic dispersion of MMT in PP matrix was verified by XRD and TEM

combined with SEM.The tensile properties were obtained by video-controlled tensile set-up

which gives true stress-strain curve.It was found that a partly intercalated and partly exfoliated structure (also called incomplete exfoliation) existed in the system.Though the tensile strength of PP nanocomposites is not much improved in engineering stress-strain curves

more than 20% increase of true stress was found in a true stress-strain experiment at high true strain

which indicates that only oriented silicate layers can have a big effect on tensile properties.Not only orientation of silicate platelets but also the degree of exfoliation is a key factor to determine the reinforcement efficiency.The reinforcement efficiency of MMT has been discussed based on the"continuum" Halpin-Tsaiequations.A good agreement was found between experimental data and theoretical prediction by changing N value(number of platelets per stack) which corresponding to different state of the dispersion of MMT in PP matrix.