Thermal, rheological, and mechanical behaviors of LLDPE/PEMA/clay nanocomposites: Effect of interaction between polymer, compatibilizer, and nanofiller

Linear low density polyethylene/maleic anhydride grafted polyethylene/montmorillonite clay (LLDPE/PEMA/clay) nanocomposites prepared using a co-rotating twin screw extruder exhibit unique thermal, rheological, and mechanical behaviors. All the mechanical properties including ductility increase with clay loading. X-ray diffraction analysis and TEM images reveal an intercalated clay structure for the LLDPE/PEMA/clay composite with 5% clay and an exfoliated structure for that with 2% clay. Differential scanning calorimetry shows that the addition of PEMA does not influence the melting temperature but favors the formation of more thin lamellas. Rheological characterization indicates that the LLDPE-PEMA blend has similar rheological behavior to neat LLDPE, implying the two polymers are completely miscible. The composites exhibit significantly higher storage and loss modulus and complex viscosity at low frequencies, and the magnitude of all these properties increases with clay loading. Furthermore, the slopes of G ', G '', and complex viscosity versus frequency are similar for the composites of different phase morphologies, suggesting that the rheological behaviors of the composites depends more on clay loading than phase morphology. The enhanced miscibility between LLDPE and PEMA, and more importantly, interfacial interaction between clay, PEMA, and LLDPE, are responsible for the distinct improvement in all the mechanical properties of the composite, and in particular for the marked improvement in ductility.