XPS analysis of the PC/PVDF interface modified by PMMA. Location of the PMMA at the interface

Polycarbonate (PC) and polyvinylidenefluoride (PVDF) are two immiscible polymers, which form two-phase polyblends with a weak interfacial adhesion and a high interfacial tension. This situation may be changed by the addition of polymethylmethacrylate (PMMA), which is miscible with PVDF and concentrates at the PVDF/PC interface. Location of PMMA at the PC/PVDF interface has been confirmed by XPS analysis, which shows that the interface enrichment in PMMA already takes place when only 10 wt% PMMA is premixed with PVDF

Particle-in-particle morphology for the dispersed phase formed in reactive compatibilization of SAN/EPDM blends

Poly(ethylene-co-propylene-co-diene) (EPDM) containing 50 wt% of poly(ethylene-co-propylene) grafted with maleic anhydride (EP-g-MA) has been melt blended with poly(styrene-co-acrylonitrile) (SAN) added with various amounts of reactive SAN, i.e. SAN bearing either primary amine (SAN-NH2) or carbamate groups (SAN-carb). Carbamate groups are precursors of primary amines by thermal thermolysis during melt processing. These reactive systems are good models for studying the effect of the kinetics of the interfacial reaction on the phase morphology. Reaction of maleic anhydride with the primary amine is indeed very fast, at high temperature, in contrast to the reaction with carbamate, which is controlled by the carbamate thermolyis into primary amine. Special attention has been paid to the experimental conditions required for the development of the particle-in-particle morphology for the dispersed phase. Depending on the mixing sequence and the grafting kinetics (NH2/MA versus carb/MA), this particular phase morphology can be forced or occurs spontaneously

Dependence of phase morphology and mechanical properties of PS/SBR/PE ternary blends on composition: transition from core-shell to triple-phase continuity structures

The weight ratio of PE and PS in ternary PS/SBR/PE blends has been changed at constant SBR content (25 wt%). When the matrix is either PE or PS, the dispersed phase has a core-shell structure with SBR forming the shell. The size of the core expectedly increases with the content of the core-forming polymer. In some composition range, the three phases are simultaneously continuous, SBR being localized in between the co-continuous PE and PS phases. The ultimate mechanical properties of the ternary blends containing SBR/PE and SBR/PS core-shell dispersed phases are close to the properties of the PS/SBR and PE/SBR binary blends, respectively. Some synergism in the elongation at break of the ternary blends is observed when core-shell SBR/PS phases are dispersed in PE matrix

Premade versus in situ formed compatibilizer at the PS/PMMA interface: contribution of the Raman confocal microscopy to the fracture analysis

The interface of a two-layer assembly of polystyrene (PS) and poly(methyl methacrylate) (PMMA) was modified by an intermediate layer of either a premade poly(styrene-g-methyl methacrylate) copolymer (P(S-g-MMA)) or a preblend of mutually reactive PS and PMMA synthesized by atom transfer radical polymerization (ATRP). No significant difference was found in the interfacial fracture toughness measured by the double cantilever beam test, although the morphology of the interfacial region was not the same when observed by transmission electron microscopy. The premade copolymer formed a distinct interphase, in contrast to the sharp interface that was observed in the case of the reactive system. The analysis of the fracture surfaces by Raman confocal microscopy showed that the fracture occurred alternatively in the PS phase and either at the PS/copolymer interface for the non reactive system or at the PS/PMMA interface for the reactive one

Microwave absorbers based on foamed nanocomposites with graded concentration of carbon nanotubes

A multilayered foamed nanocomposite with graded concentration of carbon nanotubes is proposed as a novel microwave absorber. The dispersion and foaming process enables to control the gradation in conductivity of each layer. Absorption performances are demonstrated through measurements of reflectivity and shielding effectiveness over the frequency range [8-16 GHz]. An improvement of about 5 dB in reflectivity is observed with respect to a foamed composite having a similar uniform concentration, while in both cases the shielding effectiveness is kept higher than 15 dB.Anglai

Composition effect on the core-shell morphology and mechanical properties of ternary polystyrene/styrene-butadiene rubber/polyethylene blends

The morphology of ternary polystyrene/styrene-butadiene rubber/polyethylene (PS/SBR/PE) blends has been investigated in the limits of a constant content of the major component (PS; 75 wt%) while changing the weight ratio of the two minor constitutive polymers. A core-shell structure for the dispersed phase has been predicted from the spreading coefficients and observed by transmission electron microscopy. Actually, upon increasing the relative content of PE with respect to SBR, the structure of the dispersed phase changes from a multicore structure to a PE/SBR core-shell morphology. The size of the PE subphase in the mixed dispersed phase increases sharply at a PE content that corresponds to phase inversion in the parent SBR/PE binary blends. The ultimate mechanical properties of these blends are sensitive to the strength of the SBR interphase between PS and PE. Some synergism has been observed in the PE/SBR composition dependence of the tensile strengths at yield and break