Cocontinuous Phase Morphology of Asymmetric Compositions of Polypropylene/High-density Polyethylene Blend by the Addition of Clay

A novel method of developing cocontinuous morphology in 75/25 and 80/20 w/w polypropylene/high density polyethylene (PP/HDPE) blends in the presence of small amount (0.5 phr) of organoclay has been reported. SEM study indicated a reduction in average domain sizes (D) of disperse HDPE when PP, HDPE, and the organoclay were melt-blended simultaneously at 200 degrees C. However, when the two-sequential heating protocol was employed, (that is, the organoclay was first intercalated by HDPE chains at 150 degrees C, followed by melt blending of PP at 200 degrees C), very interestingly a cocontinuous morphology was found even for very asymmetric blend compositions. WAXD study revealed the intercalation of both PP and HDPE chains inside the clay galleries, when PP/HDPE and clay were melt-mixed together at 200 degrees C. However, when the two-sequential heating protocol was used the organoclay platelets were selectively intercalated by the HDPE chains. Addition of SEPS in the blend decreased the D of HDPE domains in both the blending methods. Thus, the observed cocontinuous morphology in asymmetric composition of PP/HDPE blend in presence of clay is because of the barrier effect of the clay platelets in the HDPE phase that restrict the phase inversion into the domain/matrix morphology. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 3080-3092, 2011X112020sciescopu

Effect of organoclay platelets on morphology of nylon-6 and poly(ethylene-ran-propylene) rubber blends

The effect of organoclay platelets on morphologies of three blend compositions (80/20, 20/80, and 99.5/0.5 w/w) of nylon-6 (N6) and poly(ethylene-ran-propylene) rubber (EPR) has been studied by scanning and transmission electron micrographs. For the 80/20 (w/w) N6/ERP blend, the dispersed domain size (D) of EPR phase in the N6 matrix decreased significantly even if a small amount of the organoclay was added. The extent of the decrease in D in this blend was similar to N6/EPR blend with an in-situ reactive compatibilizer of EPR-g-maleic anhydride. The D of the blend with the clay did not change upon further annealing at high temperatures, which suggests that the clay seems to be an effective compatibilizer. But, for the 20/80 (w/w) N6/EPR blend, dispersed N6 domain did not decrease with increasing the amount of the clay up to 2 wt%. Moreover, the dispersed N6 domains were not stable against further annealing at high temperatures; thus, coalescence of N6 domains was observed. Furthermore, for 99.5/0.5 (w/w) N6/EPR blend dispersed EPR domains did not change with the amount of the clay. The results indicate that as long as the clay becomes exfoliated in the matrix, the exfoliated clay plates effectively prevent the coalescence of the dispersed domains.X11311327sciescopu

INVESTIGATION OF SURFACE MOLECULAR ORIENTATION OF POLY(DIMETHYLSILOXANE-CO-DIPHENYLSILOXANE)-MODIFIED POLY(AMIC ACID) FILMS USING DYNAMIC CONTACT ANGLE MEASUREMENTS, NEXAFS AND XPS

Since poly(dimethylsiloxane)-modified poly(amic acid) was not wetted by the photoresist, poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(amic acid) was synthesized to improve the wettability of photoresist. From a study on dynamic contact angles of water, the initial advancing contact angles on poly(dimethylsiloxane)-modified poly(amic acid) and those on poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(amic acid) are almost the same, but the equilibrium advancing contact angles on poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(amic acid) are much smaller than those on poly(dimethylsiloxane)-modified poly(amic acid). The decrease in equilibrium advancing contact angles on poly(dimethylsiloxane-co-diphenyisiloxane) appears to indicate migration of phenyl groups to the surface in the polar environment. Thus, photoresist could be wetted on the poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(antic acid) film. Near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS) were used to investigate the orientation and surface migration of molecules in poly(dimethylsiloxane-co-diphenylsiloxane).X112sciescopu

Aging behavior of oxygen plasma-treated polypropylene with different crystallinities

Oxygen plasma-treated quenched and annealed polypropylene (PP) films with different crystallinities were investigated to characterize the surface rearrangement behavior during aging using contact-angle measurements and X-ray photoelectron spectroscopy. Optimum plasma conditions were examined by varying the power, time and pressure. Less crystalline quenched PP showed a larger increase in water contact angle and a larger decrease of oxygen atomic concentration during aging than the more crystalline annealed PP, since the oxygen species, such as hydroxyl groups, introduced by oxygen plasma treatment, oriented towards or diffused faster into the bulk with lower crystallinity. The degree of crosslinking on the surface was enhanced after plasma treatment and, in addition to increased crystallinity, the crosslinked structure induced by plasma treatment restricted chain mobility and lowered the aging rate of the PP surface.X1151sciescopu

Interfacial tension reduction in PBT/PE/clay nanocomposite

We investigated the effect of organically modified nanoclay (organoclay) on immiscible polymer blends [polybutylene terephthalate (PBT)/polyethylene (PE)] with a special focus on the role of clay as a compatibilizer. When organoclay (Nanofil 919; Sud-Chemie, Inc.) is added to the blend, the clay first locates at the interface and then selectively locates in the PBT phase due to its affinity with PBT. This results in effective size reduction and narrowed size distribution of the dispersed phase. However, with a small amount of organoclay, it is observed that the clay locates at the interface regardless of its affinity for a specific component to minimize the chemical potential. The interfacial tension change of the blend with the addition of organoclay was quantitatively predicted from extensional force measurement. When the blend is subjected to an extension, the interfacial tension functions as a resistance against drop deformation. When we added organoclay to the blend, the extensional force was significantly reduced, which means that the contribution of the interfacial tension to the total force is reduced. For a 10/90 PBT/PE blend, the interfacial tension was reduced from 5.76 to 0.14 cN m(-1) when 1 wt% of organoclay was added. This interfacial tension reduction arises from the localization of the organoclay at the interface and its nonhomogeneous distribution along the interface, suppressing the coalescence between the droplets, which is a role of a compatibilizer. Conclusively, the immiscible polymer blends can be compatibilized with organoclay. The organoclay changes the blend morphology by interfacial tension reduction due to the localization of the organoclay at the interface and by the viscosity ratio change due to the selective localization by its affinity to a specific component in the blend

Modulation of neutrophil NETosis : interplay between infectious agents and underlying host physiology

The ability of neutrophils and other leucocyte members of the innate immune system to expel their DNA into the extracellular environment in a controlled manner in order to trap and kill pathogenic microorganisms lead to a paradigm shift in our understanding of host microbe interactions. Surprisingly, the neutrophil extracellular trap (NET) cast by neutrophils is very wide and extends to the entrapment of viruses as well as multicellular eukaryotic parasites. Not unexpectedly, it has emerged that pathogenic microorganisms can employ a wide array of strategies to avoid ensnarement, including expression of DNAse enzymes that destroy the lattice backbone of NETs. Alternatively, they may use molecular mimicry to avoid detection or trigger events leading to the expression of immune modulatory cytokines such as IL-10, which dampen the NETotic response of neutrophils. In addition, the host microenvironment may contribute to the innate immune response by the production of lectin-like molecules that bind to bacteria and promote their entrapment on NETs. An example of this is the production of surfactant protein D by the lung epithelium. In addition, pregnancy provides a different challenge, as the mother needs to mount an effective response against pathogens, without harming her unborn child. An examination of these decoy and host response mechanisms may open the path for new therapies to treat pathologies mediated by overt NETosis