Surface characterization of polypropylene/(ethylene–propylene) copolymer blends (PP/EP): application to injection‐moulded systems

Abstract

Polypropylene/ethylene-propylene copolymer blends (PP/EP) were characterized by time-of-flight (ToF). SIMS, by dynamic wetting and by atomic force microscopy and force modulation spectroscopy (AFM-FMM).In a first step, model systems of compression-moulded PP/EP physical blends were prepared. With these materials, ToF-SIMS provides linear relationships between the selected peak and the EP content in the material. This indicates that both phases are present at the surface in the same concentrations as in the bulk. However, the EP signal is weak. In dynamic wetting measurements with water, for each tested blend composition the advancing contact angle corresponds to that of PP and the receding contact angle corresponds to that of EP. This method is thus suitable for detecting the presence of the two phases at the surface even for low concentrations of one consituent. The force modulation image gives elastic contrasts between EP and PP and is thus able to reveal the surface morphology. In a second step, these methods were used to characterize injection-moulded PP/EP reactor blends. Both AFM-FMM and ToF-SIMS suggest that a PP skin covers EP nodules at the surface. This is confirmed by electron microscopy examinations of cross-sections. This surface phase segregation leads to the presence of PP in the first 100 nm of the surface and could be explained by preferential wetting of the mould by the phase with the lower viscosity, PP in this case. However, dynamic wetting reveals that the PP skin is not complete. Thus, a low EP concentration may be found at the surface, in the form either of EP nodules or of EP molecules having migrated through the PP skin.

“Matrix” Effects in ToF-SIMS Analyses of Styrene−Methyl Methacrylate Random Copolymers

“…SIMS characterizations of random copolymers have already been reported in the literature, but extracting relevant information on the unit contents, often based on the empirical selection of characteristic peaks, proved to be a difficult task. − Peaks have to be selected with extreme care. A study on poly(styrene- r -butadiene) showed for instance that intensity ratios of selected peaks can exhibit linear or nonlinear relationships with respect to the comonomer content .…”

Exploring Molecular Changes at the Surface of Polypropylene after Accelerated Thermomolecular Adhesion Treatments

“…Multiple strategies were used for selecting ToF-SIMS peaks to be included in the data matrix. Initially, peaks were selected on the basis of reference libraries and previous assignment in the literature for polypropylene and surface treated polypropylene − . Peaks were also assigned by using the library and the exact mass calculator tool in the Ionspec software (Ion-TOF GmbH, Germany) to identify contaminant peaks, the hydrocarbon peaks, and peaks that were likely to correspond to fragments of the flame treatment that were not listed in the literature.…”

Surface stability of polypropylene compounds and paint adhesion

“…Pressure p was determined by the type of nozzle installed at the end of the water pipe. Different vapor jet test conditions are specified for the automobile industry 6. The following conditions were used in this study: T = 60°C, t = 60 s, d = 100 mm, α = 90°, p = 68 bar, and nozzle type = 2506.…”

“…It does not contain rubber particles 4, 5. Tomasetti et al6 characterized the surface composition of PP/EPR blends: surface phase segregation should lead to the presence of mainly pure PP in the first 100 nm of the surface, but this PP skin should not be completely closed. The role of EPR in the formation of the skin layer is still speculative.…”