The Effects of Chemical Bonding of Nanoclay Surface Modifier and Compatibilizer on Microstructure Development and Rheological Properties of PP/PP-g-MA/Diamine Modified Nanoclay

Abstract

The montmorillonite (MMT) surface was modified by 1,12 diaminododecane via cation exchange reaction in order to provide a chemical potential for MMT to react with polypropylene grafted maleic anhydride, PP-g-MA, compatibilizer. The Diamine modified nanoclay (DA) was then utilized to prepare PP based nanocomposite samples using two grades of PP-g-MA with different melt flow rate, and their performances were compared with the nanocomposite samples loaded with Cloisite®20A. All nanocomposite samples were prepared by melt compounding process in a laboratory internal mixer. The XRD results of the DA containing samples prepared using both compatibilizers showed a little increase in d001 spacing of nanoclay. The sample containing DA compatibilized with low melt flow rate PP-g-MA exhibited a rheological behavior similar to its matrix. In contrast, the sample containing DA and high melt flow rate PP-g-MA showed a considerably increased complex viscosity, η*, and storage modulus, G′, in whole range of frequencies with no sign of a low frequency nonterminal behavior. The absence of rigid tail in the Cole-Cole plot of the rheological data of this sample also evidenced the absence of a 3D network microstructure. Results of FTIR analysis, performed on the samples containing DA, confirmed the occurrence of a chemical reaction between the amine groups of modified MMT and maleic group of compatibilizer with higher efficiency in the sample compatibilized with high melt flow rate PP-g-MA. From these results, it was concluded that in this sample, a special microstructure consisting of nanocaly aggregates with strong interfacial interaction to matrix is formed. This was evidenced by observation of individual aggregates in TEM micrograph.