The kinetics and the extent of side reactions of the anionic polymerization of silyl-protected 2-hydroxyethyl methacrylate, 2-(tert-butyldimethylsilyloxy)ethyl methacrylate (TBDMS-HEMA), in tetrahydrofuran (THF) were studied as a function of polymerization temperature. Lithium chloride was added in order to achieve a controlled polymerization. The results of polymerizations at various temperatures are compared with reported data for methyl methacrylate and tert-butyl methacrylate in THF. The activation energy for the studied monomer is lower compared to the other methacrylates. Gel permeation chromatography-viscosity studies show that poly(TBDMS-HEMA) exhibits a more wormlike structure in THF than other polymethacrylates, as indicated by a higher Mark-Houwink exponent, α = 1.025.
The development of the new RIM generation "Polyurea-RIM" is progressing world-wide. The reason for the superior thermal stability of the Polyurea- RIM-Elastomers is the polymerization without the use of a metallic catalyst. RIM without catalyst is only possible with the use of highly reactive species like primary and secondary amines. However, polyether with aliphatic amino end-groups are very fast and difficult to control for the RIM-process.
The excellent mechanical properties and high productivity of polyurea RIM systems allow for a broad variety of applications in the automo tive industry. Due to their high reactivity, however, these systems can lead to problems concerning the filling of large and complicated molds. Some years ago BASF/Elastogran introduced new polyurea/amide RIM systems (ELASTOLIT® R 4500 RIM series) based on polyether ketimines, which have reduced reactivity in comparison to polyethers with aliphatic pri mary amino end groups. This paper reports on research work for the new ELASTOLIT® R 4500/IF (Improved Flowability) RIM systems which are based on polyethers with secondary amino end groups. While mechanical properties remain at the level known from the polyurea RIM systems, the flowability and processability are superior even when compared to the polyether ketimine systems.
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