SURFACE STRUCTURAL STUDIES OF POLYETHYLENE, POLYPROPYLENE AND THEIR COPOLYMERS WITH TOF SIMS

Static secondary ion mass spectrometry (SIMS) was applied for probing structural differences such as unsaturation and branching in the case of simple aliphatic hydrocarbon polymers (polyethylene, polypropylene and their copolymers). The parameter introduced for quoting surface amounts of branching is the percentage of C6 to CS cluster emission relative to the sum of all C2 to C8 clusters. The ratio of the total emission of hydrogen-deficient fragments to the sum of all C2 to CS clusters is found to be a good pointer for unsaturation, especially for probing vinyl bonds. While applied successfully to polymers of the same family, these pointers cannot provide structural information on polyethylene/polypropylene copolymer surfaces in a straightforward way. The chemical surface composition of these copolymers is correlated to the percentage of the m/z 69 fragment.