In this study, we report the synergistic effect of nanoclay and maleic anhydride grafted polyethylene (PEg-MA) on the morphology and properties of (80/20 w/w) nylon 6/high density polyethylene (HDPE) blend. Polymer blend nanocomposites containing nanoclay with and without compatibilizer (PE-g-MA) were prepared by melt mixing, and their morphologies and structures were examined with scanning electron microscopy (SEM) and wide angle X-ray diffractometer (WAXD) study. The size of phaseseparated domains decreased considerably with increasing content of nanoclay and PE-g-MA. WAXD study and transmission electron microscopy (TEM) revealed the presence of exfoliated clay platelets in nylon 6 matrix, as well as, at the interface of the (80/20 w/w) nylon 6/HDPE blend-clay nanocomposites. Addition of PE-g-MA in the blend-clay nanocomposites enhanced the exfoliation of clays in nylon 6 matrix and especially at the interface. Thus, exfoliated clay platelets in nylon 6 matrix effectively restricted the coalescence of dispersed HDPE domains while PE-g-MA improved the adhesion between the phases at the interface. The use of compatibilizer and nanoclay in polymer blends may lead to a high performance material which combines the advantages of compatibilized polymer blends and the merits of polymer nanocomposites.

The electrical properties in polymer/carbon nanotube (CNT) nanocomposites are governed not only by the degree of dispersion but also to a greater extent on the aspect ratio of the CNTs in the final composites. Melt-mixing of polymer and CNTs at high shear rate usually breaks the CNTS that lowers the aspect ratio of the nanotubes. Thus, homogeneous dispersion of CNTs while retaining the aspect ratio is a major challenge in melt-mixing. Here, we demonstrate a novel method that involves melt-blending of acrylonitrile-butadiene-styrene (ABS) and in situ polymerized polystyrene (PS)/multiwalled CNT (MWCNT) nanocomposites, to prepare electrically conducting ABS/ MWCNT nanocomposites with very low CNT loading than reported. The rationale behind choosing PS/MWCNT as blending component was that ABS is reported to form miscible blend with the PS. Thus, (80/20 w/w) ABS/(PS/ MWCNT) nanocomposites obtained by melt-blending showed electrical conductivity value %1.27 Â 10 À6 S cm À1 at MWCNT loading close to 0.64 wt %, which is quite lower than previously reported value for ABS/MWCNT system prepared via solution blending. Scanning electron microscopy and differential scanning calorimetry analysis indicated the formation of homogenous and miscible blend of ABS and PS. The high temperature (100 C) storage modulus of ABS (1298 MPa) in the nanocomposites was increased to 1696 MPa in presence of 0.64 wt % of the MWCNT.

Today, we stand at the threshold of exploring carbon nanotube (CNT) based conducting polymer nanocomposites as a new paradigm for the next generation multifunctional materials. However, irrespective of the reported methods of composite preparation, the use of CNTs in most polymer matrices to date has been limited by challenges in processing and insufficient dispersability of CNTs without chemical functionalization. Thus, development of an industrially feasible process for preparation of polymer/CNT conducting nanocomposites at very low CNT loading is essential prior to the commercialization of polymer/CNT nanocomposites. Here, we demonstrate a process technology that involves in situ bulk polymerization of methyl methacrylate monomer in the presence of multi‐wall carbon nanotubes (MWCNTs) and commercial poly(methyl methacrylate) (PMMA) beads, for the preparation of PMMA/MWCNT conducting nanocomposites with significantly lower (0.12 wt% MWCNT) percolation threshold than ever reported with unmodified commercial CNTs of similar qualities. Thus, a conductivity of 4.71 × 10−5 and 2.04 × 10−3 S cm−1 was achieved in the PMMA/MWCNT nanocomposites through a homogeneous dispersion of 0.2 and 0.4 wt% CNT, respectively, selectively in the in situ polymerized PMMA region by using 70 wt% PMMA beads during the polymerization. At a constant CNT loading, the conductivity of the composites was increased with increasing weight percentage of PMMA beads, indicating the formation of a more continuous network structure of the CNTs in the PMMA matrix. Scanning and transmission electron microscopy studies revealed the dispersion of MWCNTs selectively in the in situ polymerized PMMA phase of the nanocomposites. Copyright © 2012 Society of Chemical Industry

Positive temperature coefficient of resistivity (PTCR) behavior of poly(methyl methacrylate) PMMA/silver (Ag)‐coated glass bead composites has been investigated with reference to the conventional PMMA/carbon black (CB) composites. The PMMA/CB composites showed a sudden rise in resistivity (PTC trip) at 115°C, close to the glass transition temperature (T g, 113°C) of the PMMA. However, the PTC trip temperature (92°C) of PMMA/Ag‐coated glass bead composites was appeared well below the T g of PMMA. The room temperature resistivity and PTC trip temperature of the composites were also very much stable upon thermal cycling. Addition of 1 phr of nanoclay increased the PTC trip temperature of PMMA/CB composites to 120°C, close to the T g (118°C) of PMMA/clay nanocomposites, while PMMA/clay/Ag‐coated glass bead nanocomposites showed the PTC trip at 98°C. We proposed that the mismatch in coefficient of thermal expansion (CTE) between PMMA and glass beads played a key role that led to a disruption in continuous network structure of Ag‐coated glass beads even at a temperature well below the T g of PMMA. The decrease in dielectric permittivity of PMMA/Ag‐coated glass bead composites on increasing frequency indicated possible use of the PTC composites as dielectric material. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

In this report, we introduce an industrially feasible method that involves melt blending of polycarbonate (PC) and in situ suspension polymerized exfoliated PMMA/clay (Na þ MMT) nanocomposites to prepare highly exfoliated PC/clay nanocomposites. The rational behind this is that PC is well known to form miscible blend with low molecular weight PMMA. Thus, low molecular weight PMMA/clay exfoliated nanocomposites were prepared by suspension polymerization using preexfoliated clay (Na þ MMT) in water media during the polymerization. The (80/20 w/w) PC/PMMA blends without and with Na þ MMT showed single glass transition temperature (T g ), indicating complete miscibility of the polymers in the blend. The surface morphologies of the composites were studied by scanning electron micros-copy (SEM). Wide-angle X-ray diffraction and transmission electron microscope (TEM) studies of the nanocomposites revealed delamination of the clay silicate layers in the PC matrix. The properties of the (80/20 w/w) PC/PMMA-Na þ MMT nanocomposites were significantly higher than that of the pure PC. Moreover, retention of the optical transparency of PC in the nanocomposites could be due to the presence of unmodified clay (Na þ MMT), which did not contain any organic modifier (quaternary ammonium salt) that could decompose during melt mixing of PC at high temperature (% 280 C). V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: E601-E609, 2012