No abstract

Shape memory polymers (SMPs) are introduced as polymers that have the ability to return to their early programmed shape after exposure to an external stimulus. Enhancement of the material with nano-clay filler has improved its thermomechanical properties and increased the range of its applications in many fields of industry. Due to the tiny size of filler and the heterogeneous nature of the material structure at different scale levels, characterizing the material’s thermomechanical flow using conventional experimental equipment is a far-fetched task. Furthermore, providing one numerical model that is able to simulate the material thermomechanical behavior by including all the effects of the lower scale material structure is also very hard. In this study, a two-scale modeling approach is developed by a combination of the numerical homogenization scheme, 3D Representative Volume Element (RVE) concept, and finite element method. The effects of the filler weight fractions on the overall effective elastic constants as well as the material flow under a finite deformation are investigated. The resulting elastic constants and the stress–strain curves show a fairly good agreement with the analytical results. Furthermore, all the investigated results provide a deep understanding of the material behavior and a starting point for the next higher scale level modeling approaches.

Polypyrrole/silver (PPy/Ag) nanocomposites was synthesized via a chemical oxidative method. The AFM analysis is performed to study the surface roughness, morphology and size distribution of the PPy particles and PPy-ag nanocomposites. The results indicated that as the concentration of Ag in the nanocomposite increases, the roughness also increases. The size of nanoparticles was also evaluated and found in the range of 15 nm to 125 nm. The PPy/Ag nanocomposites exhibited an effectiveness against Gram-negative Escherichia coli showing an inhibition zone of 4mm and displayed poor efficacy against Gram-positive Staphylococcus aureus. Based on given adequate antibacterial characteristics of PPy/Ag nanocomposites, it can be identified as a promising material in biomedical applications.

Polypyrrole and polypyrrole / silver nanocomposites were fabricated by in-situ polymerization employing Ammonium Persulphate as an oxidizing agent. Nanocomposites were synthesized by combining polypyrrole and silver nanoparticles in various weight percentages (0.1%, 0.5%, 3%, 5% and 7% wt.). Crystallographic data were collected using X-ray diffraction.  PPy particles were found to have an orthorhombic symmetry. In contrast, PPy/Ag nanocomposites were reported to have monoclinic structure. The crystallite size was determined by XRD using Scherrer equation and considered to be within 49 nm range. DC conductivity of pelletized samples was evaluated in the temperature range of 323.15k to 453.15k. The conductivity displayed an increase when the temperature is increased from 323.15k to 453.15k. Activation energies were determined from plots of Arrhenius for all nanocomposites. The findings indicated that the activation energy decrease with increasing the weight percentage of Ag nanoparticles in the nanocomposites.