On the filler flocculation in silica and carbon black filled rubbers: Part II. Filler flocculation and polymer-filler interaction

Filler flocculation and polymer-filler interaction in silica and carbon black filled rubbers containing different functional end-groups were investigated. Lithium-hexamethyleneimine initiated polymers terminated with a proton (HMI-P-H), SnCl4 (HMI-P-Sn), and a mixture of SnCl4 and tetraethyl orthosilicate (HMI-P-TEOS) were employed to determine the affinities of various functionalities toward fillers. Reduced filler flocculation was found for compounds of HMI-P-Sn and HMI-P-TEOS after thermal annealing at 171degreesC for 15 minutes when compared to the annealed HNH-P-H stock. Curing at the same condition used for annealing gave further suppression of filler flocculation for HMI-P-TEOS stock by increased polymer-filler interaction during cure. Polymer-filler interaction was followed by examining G' strain dependence and the differences in G' obtained between HMI-P-Sn or HMI-P-TEOS and HMI-P-H (deltaG'). This treatment gave a peak maximum in the deltaG' plot as a function of strain. The magnitude of the maximum in HMI-P-TEOS stock is double that of HMI-P-Sn stock and increased after thermal annealing. The compound tandelta temperature dependence showed higher hysteresis around the T-g transition and strong dependence at elevated temperatures was found for HMI-P-TEOS stocks. This increased polymer-filler interaction is manifested with increased 0degreesC tandelta and reduced 50degreesC tandelta which relates to the improved wet traction and rolling resistance for tires.