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Surface characterization of polypropylene/(ethylene–propylene) copolymer blends (PP/EP): application to injection‐moulded systems
Author(s) -
Tomasetti E.,
Nysten B.,
Rouxhet P. G.,
Poleunis C.,
Bertrand P.,
Legras R.
Publication year - 1999
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/(sici)1096-9918(199908)27:8<735::aid-sia567>3.0.co;2-m
Subject(s) - wetting , polypropylene , contact angle , materials science , copolymer , scanning electron microscope , morphology (biology) , viscosity , phase (matter) , polymer chemistry , chemical engineering , analytical chemistry (journal) , composite material , chemistry , chromatography , organic chemistry , polymer , genetics , engineering , biology
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. Copyright © 1999 John Wiley & Sons, Ltd.