Polypropylene (PP) and acrylonitrile-butadiene-styrene (ABS) blends with multiwall carbon nanotubes (MWNT) were prepared by melt mixing. PP/ABS blends without MWNT revealed coarse co continuous structures on varying the ABS content from 40 to 70 wt %. Bulk electrical conductivity of the blends showed lower percolation threshold (0.4-0.5 wt %) in the 45/55 co continuous blends whereas the percolation threshold was between 2 and 3 wt % in matrix-particle dispersed morphology of 80/20 blends. Interestingly, droplet size was observed to decrease with addition of MWNT above percolation threshold in 80/20 blends. Further, the bulk electrical conductivity was found to be dependent on the melt flow index of PP. The non-polar or weakly polar nature of blends constituents resulted in the temperature independent dielectric constant, dielectric loss, and DC electrical conductivity. Rheological analysis revealed the formation of 3D network-like structure in 80/20 PP/ABS blends at 3 wt % MWNT. An attempt was made to understand the relationship between rheology, morphology, and electrical conductivity of these blends.

Phase morphology of melt-mixed polypropylene (PP)/acrylonitrile-butadiene-styrene (ABS) blends was found to be blend ratio dependent, viz., matrix-particle dispersed type of morphology which was observed up to 30 wt % of ABS level beyond which the morphology showed co-continuous type. The domain size of 80/20 PP/ABS blends was found to decrease significantly at 10 wt % carbon black (CB) level, and in case of 70/30 blends morphology was transformed into co-continuous type in the presence of CB, which was retained up to 60 wt % ABS. The finer morphological features were associated with the compatibilizing action of CB particles. Continuous network was achieved through aggregated CB particles predominantly in the PP phase wherein one could find CB-rich PP phase and CB-less PP phase. Solution experiments further supported the existence of CB particles preferentially in the PP phase. AC electrical conductivity measurements indicated a 3D network-like structure of CB aggregates in the co-continuous compositions which showed enhanced electrical conductivity as compared to the matrix-dispersed type of morphology in 80/20 PP/ ABS blends which exhibited insulating behavior. On increasing ABS content in the blends the electrical conductivity decreased progressively due to a difficulty in retaining 3D continuous network of CB aggregates especially at 40/60 composition. Increased processing temperature led to a higher electrical conductivity in the respective blends. Dielectric measurements revealed the existence of metallic type of conduction in the co-continuous compositions. However, 80/20 blends showed low e 0 value. Overall, structure property relationship studies were conducted in PP/ABS blends with CB.

ABSTRACT:Crystallization of polypropylene (PP) in unvulcanized blends of PP with the butadiene-styrene block copolymer (SBS) was studied through differential scanning calorimetry (DSC) and X-ray diffraction measurements in the composition range of 0 -40 wt % SBS content. Analysis of the crystallization exotherms revealed variation in the crystallization behavior, crystallinity, and crystalline morphology of the PP component in the blends at various levels of SBS concentration. The crystallinity determined by X-ray diffraction and DSC showed identical variations with the blend composition. The tensile and thermal properties of the blends were studied in the entire composition range. Correlations of the tensile properties with the crystallization parameters of the PP component in the blends are also presented.

Unvulcanized and dynamically vulcanized blends of isotactic polypropylene (PP) and butadiene styrene block copolymer (SBS) in the composition range of 10-40 wt % SBS were prepared by melt mixing in an internal mixer and evaluated for impact and tensile properties. Dynamic vulcanization of blends gave superior mechanical properties. Systematic changes with varying blend composition were found in stress-strain behavior in both the blend systems. The effect of blend composition on the state of dispersion and morphology of the dispersed phase droplets were studied by scanning electron microscopy. Analysis of the yield stress data in terms of various theoretical models revealed the variation of stress concentration effect with blend composition and higher interphase adhesion in dynamically vulcanized blends.

Polypropylene (PP) is one of the most useful general purpose plastics. However, the poor transparency and brittleness of PP restricts its applications in the field of medical and personal care where silicone and polyvinyl chloride (PVC) are presently used. This work concentrates on developing highly transparent elastomeric PP blends and also thermoplastic elastomer by blending isotactic polypropylene (I‐PP) with styrene/ethylene‐butylene/styrene (SEBS) triblock copolymer. PP/SEBS blend derived from high melt flow index (MFI) PP and high MFI SEBS exhibit remarkable transparency (haze value as low as 6%) along with good percentage of elongation and processability. The reduction in difference of refractive index (RI) between PP and SEBS has been observed by blending SEBS with PP. The wide angle X‐ray diffraction studies show that there is significant reduction in the percentage crystallinity of PP by the addition of SEBS block copolymer. Temperature‐dependent polarized light microscopy studies reveal the reduction in spherulites size by the addition of SEBS block copolymer. Transmission electron micrographs show that the SEBS polymer forms a fine lamellar structure throughout the PP matrix with phase inversion at higher SEBS concentration. Development of phase morphology, crystalline morphology, and crystallinity in different blends has been analyzed and microstructure‐haze correlations have been developed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Blends of polypropylene/ethylene octene comonomer (PP/EOC) with conducting fillers viz., carbon black (CB) and multiwall carbon nanotubes (MWNT) were prepared using melt mixing technique with varying filler concentration and blend compositions. Thermo gravimetric analysis studies indicated that presence of filler enhanced the thermal stability of PP/EOC blends. Morphological analysis revealed the formation of matrixdispersed droplet and co-continuous type of morphology depending on the blend compositions. Significant reduction in droplet size and finer ligament thickness in co-continuous structure were observed in the blends with filler due to compatibilization action. Fillers were found to be aggregated in the EOC phase irrespective of blends compositions and could be related to the affinity of the fillers toward EOC phase. The electrical conductivity of PP/EOC blends with CB and MWNT was found to be highest for 80/20 composition and decreased as EOC content increased. The percolation threshold of CB was between 10 and 15 wt% for the 80/20 and 70/30 blends whereas it was 15-20 wt% for blends with EOC content higher than 30 wt%. The percolation threshold was 2-3 wt% MWNT for PP/EOC blends. This was attributed to the aggregated filler network preferentially in the EOC phase. The melt-rheological behavior of PP/EOC blends was significantly influenced in presence of both the fillers. POLYM. ENG. FIG. 8. Melt rheological response for 80/20 PP/EOC blends with 0.5 and 3 wt% MWNT: (a) g*; (b) G 0 . FIG. 9. Melt rheological response for 55/45 PP/EOC blends with 0.5 and 3 wt% MWNT: (a) g*; (b) G 0 .

Synthesis and characterization of polymer nanocomposites consisting of diglycidyl ether of bisphenol-A with inorganic as well as organically modified nanosized clay fillers, for example, vermiculites and montmorillonite, obtained from trade, are studied. Confirmations of intercalation and exfoliation characteristics of these fillers into the cured epoxy resin matrix have been investigated by wide angle X-ray diffraction studies. Scanning electron microscopy and atomic force microscopy techniques have been adopted to assess the nature of filler dispersion, size of the agglomerates, and the polymer-filler adhesion. While significant improvement in the mechanical properties (i.e., tensile, flexural strength, and modulus) has been observed, the thermo-oxidative stability of the composites measured by thermogravimetric analysis showed only marginal improvement. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: [3236][3237][3238][3239][3240][3241][3242][3243][3244] 2012

Unvulcanized and dynamically vulcanized blends of isotactic polypropylene (PP) and butadiene-styrene block copolymer (SBS), in the composition range of 10-40 wt % SBS content are prepared in an internal mixer and the vulcanization process is investigated through time-torque curves. Study of melt rheological properties of these blends are reported, and results show the effects of blend composition and shear rate on melt viscosity and melt elasticity. Blending of PP with SBS increases melt viscosity and decreases extrudate distortion. Dynamically vulcanized blends show higher melt viscosity and lower melt elasticity than corresponding unvulcanized blends with no melt fracture in the studied range.