This work is conducted to obtain mechanical properties of microtubule. For this aim, interaction energy in alpha-beta, beta-alpha, alpha-alpha, and beta-beta dimers was calculated using the molecular dynamic simulation. Force-distance diagrams for these dimers were obtained using the relation between potential energy and force. Afterwards, instead of each tubulin, one sphere with 55 KDa weight connecting to another tubulin with a nonlinear connection such as nonlinear spring could be considered. The mechanical model of microtubule was used to calculate Young’s modulus based on finite element method. Obtained Young’s modulus has good agreement with previous works. Also, natural frequency of microtubules was calculated based on finite element method.

Isothermal crystallization kinetics, melting, structure and dynamic mechanical properties of a polypropylene (PP) random copolymer were studied. In order to study the effect of cooling rate on melting, two different cooling rates were applied to the samples. While water cooled samples revealed a broad single melting endotherm with  a-crystalline structure, the slow cooled samples showed a shoulder at lower temperature followed by a sharp melting endotherm and a mixture of a and g-crystalline phases. The effect of annealing on log E of the b-relaxation for the PP copolymer showed that the b-transition increased in intensity with increasing annealing temperature. No considerable difference was found in the activation enthalpy of relaxation, ΔH, values for the annealed compared to that of the water cooled samples using the Arrhenius equation. The isothermal crystallization kinetics was also studied for PP and the values of nucleation constant, Kg, and end-surface free energy of the crystal growth, se, were calculated using Lauritzen-Hofffman theory.

In order to increase the processability and mechanical properties of poly (vinyl chloride) (PVC), the terpolymer of acrylonitrile-chlorinated polyethylene-styrene (ACS) is used to modify the PVC. The plasticizing, rheological, and dynamic mechanical properties of PVC/ACS blends are investigated by means of torque rheometer, oscillation rheometer, and dynamic mechanical analyzer. The measurements of torque rheometer showed that both plasticizing time and stabilization torque are decreased with increasing ACS content. The PVC/ACS melts displayed larger dynamic storage modulus (G’), loss modulus (G”), and complex viscosity ( h*) than that of pure PVC, and these values reached maximum for the blend with 10 wt% ACS. When ACS content was below 10 wt%, PVC and ACS showed good compatibility in the blends by displaying a single T g; however, when ACS content was more than 15 wt%, the phase separation phenomena occurred in the blends. PVC/ACS blends showed larger storage modulus (E′) and loss modulus (E”) than that of pure PVC, but these values decreased with increasing ACS content. ACS can enhance both tensile and impact strength of PVC, and the impact strength reached maximum with 15 wt% ACS content which is higher 2.5 kJ/m2 than the pure PVC. These results suggested that ACS is an efficient processing aid and toughening modifier for PVC at appropriate content.

This paper is devoted to the study of dynamic mechanical behaviour of two metallocene polyethylenes (m-PE). For this purpose two metallocene linear low density polyethylene (m-LLDPE) and very low density polyethylene (m-VLDPE) were used consisting of 3.3 mol% butyl and 6 mol% ethyl branches, respectively. The m-LLDPE showed three transitions at 31, -8 and –115°C attributed to the α, β and γ-transitions, respectively. The β-relaxation was observed as a shoulder on the α-relaxation peak. Studies on the m-VLDPE revealed no appreciable α-relaxation but an increased β-relaxation than that of the m-LLDPE. The effects of cooling rate and annealing were also investigated for the m-LLDPE. Slow cooled sample showed a higher α-relaxation temperature and was appreciably greater in breadth and area than that of the sample cooled in water. No appreciable shifts in either the a orβ-relaxation temperature were found by comparing loss modulus of quenched and annealed sample of the m-LLDPE. The time-temperature superposition principle was also found to be applicable to the α-relaxation process of the m-LLDPE and master curve was obtained at 80°C.

In this study, effect of MAPE (maleic anhydride polyethylene) as the compatibilizer ‎on the mechanical properties of wood-flour polyethylene composites has been ‎investigated by suing Dynamic Mechanical Analysis (DMA). Composites were made ‎at 25% and 50% by weight fiber contents and 1% and 2% compatibilizer respectively. ‎Controls were also made at the same fiber contents without the compatibilizer. Static ‎mechanical tests including tensile and bending tests were performed. Temperature ‎scans in the range of -110 to +100°C was also conducted. Results indicated ‎improvements in the mechanical properties due to the compatibilizer addition. Storage ‎modulus values were higher in the case of coupled composites especially at 50% fiber ‎loading. Glass transition was hard to detect in all composite systems while increasing ‎fiber content slightly shifted alpha transition to higher temperatures. MAPE had ‎negligible effects on the main transitions but the effect of fiber content on the ‎intensity and temperature of alpha transition seemed to be proportional to the fiber ‎content. Mechanical loss factor spectra showed that at 50% fiber content, the ‎compatibilizer caused a reduction in tan#d values indicating less energy loss when the ‎compatibilizer was present‏.‏