In-situ monitoring by fibre-optic NIR spectroscopy and rheometry of maleic anhydride grafting to polypropylene in a laboratory scale reactive extruder

The graft copolymerisation of maleic anhydride (MAH) onto polypropylene (PP) has been studied in situ by interfacing a laboratory scale mini-extruder/processor with a near-infrared (NIR) spectrometer via a fibre optic link. Apparent viscosity was measured simultaneously with the NIR spectra. The graft reaction was carried out at several temperatures with and without the initiator, dicumyl peroxide (DCP). Analysis of the NIR spectra showed the reaction to be first order with respect to MAH, and that the graft reaction rate was not affected by the presence of DCP. However, DCP caused a large increase in chain scission reactions leading to a dramatic drop in apparent viscosity. In the absence of DCP, scission reactions occurred at a slower rate and the apparent viscosity remained steady, after an initial drop, for about 15 min during the early part of the reaction. We suggest that a possible explanation for this might be a “repair mechanism” involving the reaction of two PP macro-radicals with a single MAH moiety, thus maintaining the molecular weight. Once the concentration of MAH drops, this reaction becomes less significant and scission reactions dominate.     

Tris-[3-hydroxy-1,2-dimethyl-pyridin-4(1H)-onato]cobalt(III)

The preparation and properties of tris-[3-hydroxy-1,2-dimethyl-pyridin-4(1H)-onato]cobalt(III) are described. The structure of the fac isomer has been established by X-ray diffraction techniques. Solvation characteristics of this complex have been assessed through solubility measurements in methanol–water mixtures. The complex is very inert in neutral solution but undergoes acid-catalysed aquation at lower pHs.     

Raman microspectroscopic mapping: a tool for the characterisation of polymer surfaces

Raman mapping by point illumination of polymer surfaces is discussed with examples taken from the plasma treatment of polypropylene (PP) and subsequent grafting of polystyrene (PS). Maps can be constructed for surface properties such as crystallinity, blend components and distribution of grafted PS. The Raman sampling volume was estimated for confocal operation using a 50x objective lens.