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Films composed of a mixture of poly(methyl methacrylate) (PMMA, My, = 306 000) and polystyrene (PS, My, = 234 000) were prepared by solvent casting. In these films, the PMMA component, covalently labeled with a fluorescent dye, comprised 10 wt % of the mixture. These films were examined by laser confocal fluorescence microscopy (LCFM). At depth greater than 5-6 pm below the surface, the blend morphology was one of tiny PMMA spheres dispersed in a continuous PS matrix. These spheres were randomly distributed in space and were characterized by a broad size distribution. At the surface, the morphology was very different. The PMMA was present in the form of large spheres, 5-6 pm in diameter, characterized by not only a very narrow size distribution but a strong periodicity in their location. The broad distribution of small particles in bulk can be attributed to phase separation by a nucleation and growth mechanism coupled with the small surface energy between PS and PMMA. At the surface, two other and larger surface energies come into play, those of PS/air and PMMA/air. In addition, more rapid evaporation of solvent from the surface may lead to a spinodal decomposition mechanism for surface phase segregation.

Dimethylaminoethyl methacrylate (DMAEMA) was investigated as a prospective coupling agent for mica-reinforced polypropylene. Composites prepared with the widely-used silane coupling agent, N-(4-vinylphenyl) methyl-N'-(3-trimethoxysilylpropy1)ethylenediamine monohydrochloride (2-6032), were compared with the amino-coupled composite. Improvements in the flexural properties at room temperature were observed with the two coupling agents: a 22 percent increase in the strength with the silane compared to a 16 percent increase with DMAEMA. Cone-and-plate viscometry at 220°C showed that the addition of coupling agents greatly reduces the viscosity of the composite: a 50 percent decrease was obtained with the silane-treated composite and a 20 percent decrease with DMAEMA.

Two orienting techniques for stiffening semicrystalline polymers, rolling and die-drawing, are compared with respect to the anisotropy they produce in isotactic polypropylene (PP). Billets of PP were either drawn at 145°C through a tapered slotted die in the Leeds large-scale die-drawing machine to reduction ratios R of 2.2, 5.1 and 7.6, or rolled between rolls of 65 mm diameter at 120°C to R = 2 to 5. Drawing increased the crystallinity, as estimated from differential scanning calorimetry, density and wide-angle X-ray diffraction (WAXD); it thus disrupts the original PP structure, developing a n oriented crystalline structure. WAXD pole figures showed that both die-drawing and rolling oriented the molecular chain axis nearly parallel to the machine direction and the b axis perpendicular to the drawing plane. This approximate uniaxial symmetry was confirmed by ultrasonic measurements of the stiffness matrix. In tensile and falling-dart impact tests, samples failed by delaminating in the drawing plane. Although stresses are applied to the material in quite different ways in die-drawing and in rolling, the geometry of deformation in both is similar, close to plane strain.