Rate of the activated anionic polymerisation of ε-caprolactam onto an isocyanate bearing polypropylene in the melt

This paper concerns the rate of the activated anionic polymerisation of ε-caprolactam (CL) onto 3-isopropenyl-α,α-dimethylbenzyl isocyanate bearing PP (PP-g-TMI) in the melt to form a graft copolymer with PP as backbone and PA6 as grafts. The polymerisation was catalysed by sodium ε-caprolactam (NaCL). The PP-g-TMI/NaCL/CL polymerisation system being heterogeneous, the polymerisation was carried out in a batch mixer. Emphasis was placed on the effects of temperature and the concentrations of NaCL and the isocyanate group in the form of PP-g-TMI on the polymerisation rate. Results suggested that if the polymerisation is to be carried out by a reactive extrusion process whose mean residence time is less than a few minutes, it is recommended that the polymerisation temperature be higher than 220 °C. Moreover, the molar ratio between NaCL and CL should be higher than 0.5 and at the same time that between the isocyanate group in the form of PP-g-TMI and NaCL, should be smaller than 4.