On the Filler Flocculation in Silica and Carbon Black Filled Rubbers: Part II. Filler Flocculation and Polymer-Filler Interaction

Abstract

Abstract 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 171 °C for 15 minutes when compared to the annealed HMI-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 (δG′). This treatment gave a peak maximum in the δG′ 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 tanδ temperature dependence showed higher hysteresis around the Tg transition and strong dependence at elevated temperatures was found for HMI-P-TEOS stocks. This increased polymer-filler interaction is manifested with increased 0 °C tanδ and reduced 50 °C tanδ which relates to the improved wet traction and rolling resistance for tires.