Low molar mass polybutadiene made crosslinkable by the introduction of styrenic moieties via urethane linkage: synthesis, kinetic and crosslinking studies

The introduction of styrenic moieties was chosen for the radical crosslinking of polybutadiene bearing hydroxy functions. The modifications were carried out with 3-isopropenyl-α,α-dimethylbenzyl isocyanate (TMI) with or without catalyst (DBTL). A 2nd order kinetic fits our experimental results up to high conversion. Arrhenius parameters were calculated. Thermally catalyzed crosslinking was studied. The reaction was followed by measuring swelling (Q) in toluene as well as mechanical parameters (storage modulus E′ at the rubbery plateau and tanδ). The influence of temperature, the nature and concentration of initiators, the number of styrenic groups per chain (n=1.2, 2, 2.4) were investigated. In the range of our experimental conditions, a “reaction master curve” was established to predict the evolution of E′ and Q as a function of time, for any temperature, initiator concentration and value of n.