Two types of commercial multiwall carbon nanotubes (MWCNTs), Baytubes® C70P and C150P were incorporated into polypropylene (PP) using melt blending technique that employs a twin screw extruder (TSE) to prepare the nanocomposites of two different concentrations (1 and 3 wt%). Subsequently, American Society for Testing and Materials (ASTM) standard samples were prepared with an injection molding machine. The prepared nanocomposites were characterized by their rheological and electrical properties using a rheometer and a picoammeter/voltage source, respectively. The effect of different types of MWCNTs and loading percentage in rheological and electrical properties was investigated in detail. The rheological analysis demonstrated a considerable dependence of the melt rheological properties of the PP/MWCNTs nanocomposites on the MWCNTs loading. The storage modulus (G′), loss modulus (G″) and complex viscosity |η*| increased with increasing MWCNTs loading. In addition, type C70P exhibited superior rheological properties compared to C150P. In terms of electrical properties, the addition of MWCNTs in the PP matrix decreased the volume resistivity of the matrix in a manner, proportional to the MWCNTs loading. No significant difference in volume resistivity was observed between the MWCNTs types. POLYM. ENG. SCI., 54:1134–1143, 2014. © 2013 Society of Plastics Engineers

Polypropylene (PP)/calcium carbonate (CaCO 3 ) nanocomposites were prepared from masterbatch by melt blending in a twin-screw extruder. The effect of three different nano-CaCO 3 loadings (5, 10, and 15 wt%) on the rheological/viscoelastic and mechanical properties of the nanocomposites was investigated. A scanning electron microscopy was used to study the morphology of the nanocomposites, whereas a differential scanning calorimetry was used to analyze the thermal properties. The rheological properties were characterized using an oscillatory rheometer, and the mechanical properties were characterized by a tensile test machine. In the melt rheological study, a frequency sweep test showed that the complex viscosity à j j, the storage modulus (G 0 ), and the loss modulus (G 00 ) of the nanocomposites increased with nano-CaCO 3 loading. The increase in à j j was approximately 1.4-1.9 times greater than that of the PP matrix. Shearthinning behavior was also observed for the nanocomposite samples. Additionally, the relaxation time spectrum and the relaxation modulus, G(t), were determined by fitting experimental data (G 0 and G 00 ) using the Maxwell element method via numerical analysis. The results showed that the time required for stress relaxation of the nanocomposites was longer than that of the matrix. In the solid viscoelastic study, dynamic mechanical thermal analysis results showed that the G 0 value of the nanocomposites increased by approximately 15-25% compared with that of neat PP. The tensile test results showed an improvement in the tensile modulus and toughness (especially at 10 and 15 wt%), Downloaded from while the tensile strength showed a moderate decrease. On the other hand, the incorporation of nano-CaCO 3 in the PP matrix has enhanced the overall flexural and Izod impact properties of the nanocomposites.

Differential Scanning Calorimetry (DSC) was used to evaluate the crystallization behavior of poly(lactic acid) and its blends with elastomer. It has been observed that the cold crystallization temperature of the blends decreased as the weight fraction of elastomer increased as well as the onset temperature of cold crystallization also shifted to lower temperature. In non-isothermal crystallization experiments, the crystallinity of poly(lactic acid) increased with a decrease in the heating and cooling rate. The melt crystallization of poly (lactic acid) appeared in the low cooling rate (1, 5 and 7.5°C/ min). The presence of low elastomer tends also to increase the crystallinity of poly (lactic acid). The DSC thermogram at ramp of 10°C/min showed the maximum crystallinity of poly(lactic acid) is 36.95% with 20 wt% elastomer contents in blends. In isothermal crystallization, the cold crystallization rate increased with increasing crystallization temperature in the blends. The Avrami analysis showed that the cold crystallization was in two stages process and it was clearly seen at low temperature. The Avrami exponent (n) at first stage was varying from 1.59 to 2 which described a one-dimensional crystallization growth with homogeneous nucleation, whereas at second stage was varying from 2.09 to 2.71 which described the transitional mechanism to three dimensional crystallization growth with heterogeneous nucleation mechanism. The equilibrium melting point of poly (lactic acid) was also evaluated at 176°C.