Shahin Akhlaghi

Effect of ZnO nanoparticles on kinetics of thermal degradation and final properties of ethylene–propylene–diene rubber systems

The morphology, thermal degradation behavior in addition to static and dynamic mechanical properties of various ethylene–propylene–diene (EPDM) rubber compounds containing nano-zinc oxide (NZnO) were investigated compared to those of EPDM with ordinary-sized ZnO (OSZnO). The field-emission scanning electron microscopy studies showed that unlike the conventional system, the formation of large size ZnO agglomerates was discouraged for NZnO filled systems. Thermogravimetric analysis (TG) revealed that the thermal degradation of EPDM system was delayed upon the inclusion of NZnO instead of OSZnO in the compound. The kinetic analysis of TG data based on Friedman and Kissinger methods showed that the nanocomposite samples exhibited higher activation energy (Ea) and lower order of reaction (n) over the conventional system, suggesting the enhancement of thermal stability upon decreasing ZnO particle size. The results obtained from dynamic mechanical analysis and static mechanical characterizations in terms of hardness, resilience, and abrasion tests interestingly indicated that NZnO not merely could act as a thermal insulator, but also could perform as a nano-filler to improve the final performance of EPDM elastomers.

Effect of hydroxyapatite nano-particles on morphology, rheology and thermal behavior of poly(caprolactone)/chitosan blends.

The effect of hydroxyapatite nano-particles (nHA) on morphology, and rheological and thermal properties of PCL/chitosan blends was investigated. The tendency of nHA to reside in the submicron-dispersed chitosan phase is determined using SEM and AFM images. The presence of electrostatic interaction between amide sites of chitosan and ionic groups on the nHA surface was proved by FTIR. It is shown that the chitosan phase is thermodynamically more favorable for the nano-particles to reside than the PCL phase. Lack of implementation of Cox-Merz theory for this system shows that the polymer-nano-particle network is destructed by the flow. Results from dynamic rheological measurements and Zener fractional model show that the presence of nHA increases the shear moduli and relaxation time of the PCL/chitosan blends. DSC measurements showed that nHA nano-particles are responsible for the increase in melting and crystallization characteristics of the PCL/chitosan blends. Based on thermogravimetric analysis, the PCL/chitosan/nHA nano-composites exhibited a greater thermal stability compared to the nHA-free blends.

Thermal Behavior and Degradation Kinetics of Compatibilized Metallocene-Linear Low Density Polyethylene/Nanoclay Nanocomposites

Morphology, thermal degradation and kinetics of metallocene-linear-low-density polyethylene (m-LLDPE)/m-LLDPE-graft-maleic anhydride (m-LLDPE-g-MA)/nanoclay nanocomposites were compared with m-LLDPE/nanoclay, m-LLDPE-g-MA/nanoclay and m-LLDPE/m-LLDPE-g-MA systems. X-ray diffraction measurements revealed intercalated and “highly intercalated” morphologies for the nanocomposites. Thermogravimetric analysis demonstrated that although thermal degradation of m-LLDPE systems were delayed upon the inclusion of nanoclay in air, an inverse effect was perceived for the nanoclay under inert atmosphere. This conclusion was supported by kinetic analysis in terms of reaction order and activation energy. The results obtained from kinetics models also put forward the contribution of m-LLDPE-g-MA, as a compatibilizer, to the thermal stability enhancement through inter-molecular cross-linking augmentation.