Surface‐directed morphology evolution in ternary blends of polyethylene, polypropylene, and ethylene–propylene copolymer: A study by laser scanning confocal fluorescence microscopy

Abstract

With laser scanning confocal fluorescence microscopy, we demonstrate a novel type of morphology evolution in moderately thick films (70 -100 m) of ternary blends of polypropylene (PP), polyethylene (PE), and ethylene-propylene rubber (EPR), in which EPR is labeled with a benzothioxanthene dye (HY-EPR). The blends are prepared by solution blending, and the phase morphology evolves during the annealing of the blend films in a stainless steel mold. Our results indicate that wetting of the mold surface is a driving force in morphology evolution for the two blend compositions investigated. For 81/14/5 PP/PE/HY-EPR, phase evolution within the mold results in a laminar structure and hydrodynamic channels, features which have previously been found in thin films of polymer blends as a result of surface-directed spinodal decomposition. In a blend with a lower weight fraction of the dispersed phase (92/7/1 PP/PE/ HY-EPR), we find that the PE/HY-EPR domains are larger and more polydisperse closer to the surface because of wetting of the mold wall. We also show that the phase morphology in these films can be controlled by the nature of one or both of the surfaces being varied. When one of the mold surfaces is replaced with a thin film of PP homopolymer, we observe draining of PE/HY-EPR from the PP to the mold surface, which results in a bilayer structure. A trilayer morphology is likewise obtained by the replacement of both mold surfaces with PP. We also carry out three-dimensional image reconstruction on a single PE/HY-EPR particle within the 81/14/5 PP/PE/HY-EPR blend to obtain detailed information on the interphase structure. We find that HY-EPR of this composition (30/70 ethylene/propylene) fully coats the PE dispersed phase and partially penetrates the PE droplets. This result falls between the interphase structures found for previously investigated EPR compositions (40/60 and 80/20 ethylene/ propylene).

Dispersion of particles in the coatings characterized by laser scanning confocal micrscopy (LSCM) I: Vertical dispersion of particles in the coatings and the weathering property studied by orthogonal analysis method of LSCM

“…The surface epoxy around the pigments first is missing during the weathering test (5). Then the pigments in the surface layer start to lose (6). The pigment poor region is exposed to the air, causing substantial decrease in gloss.…”

“…Laser scanning confocal microscopy (LSCM) is an emerging tool to characterize the morphology and structure of polymers [5][6][7]. It can not only take the image of the surface, but also take photos at different depths and reconstruct them into 3D images.…”

Surface energy inducing asymmetric phase distribution in films of a bynary polymeric blend

“…A morphology evolution of the labeled EPR (HY-EPR) by spinodal decomposition similar to those usually observed in very thin films (thickness!0.1 mm) was reported for PE/P-P/EPR ternary blend films with a thickness of 100 mm annealed at 175 8C between surfaces at different polarity [7,8]. A lamellar morphology was found in films annealed for long time between surfaces made by stainless steel or PP with the draining of the HY-EPR/PE core shell phase from the PP interface.…”

Rubber–Plastic Blends: Structure–Property Relationship

“…A volume of the sample is scanned layer by layer and reconstruction of the layers allows for the three-dimensional image. A variation of this method (laser scanning confocal microscopy) was employed to observe the morphology of PP/PE/EPR with EPR labeled with a fluorescent dye [63]. Laser scanning confocal microscopy was used to observe the spinodal decomposition of a styrene-butadiene rubber (SBR)/polybutene (PB) blend cooled from above the UCST to the unstable region showing the development of bicontinuous morphology [64].…”