| The purpose of this research was to develop steric stabilizers for polyolefin-asphalt emulsions to prevent gross phase separation at high storage temperatures.;Three asphalts from Western Canada were analyzed before any steric stabilizers were designed. All three asphalts as it turned out were very similar in their chemical composition. Their solubility parameters however. were not sufficient to identify an asphalt-miscible polymer which was needed as the soluble portion of an effective steric stabilizer. Only low molecular weight polymers were soluble due to their increased entropy of mixing.;Both hydrogen bonding and charge transfer specific interactions were considered in order to enhance the solubility of higher molecular weight polymers. However, hydrogen bonding interactions are not very effective at elevated temperatures and charge transfer complexes were deemed unattractive due to the exotic nature of acceptor-type polymers.;Therefore, the in situ production of steric stabilizers was adopted as the preferred method. Simultaneous crosslinking and grafting of low molecular weight polydienes in the asphalt phase produced a soluble half for a steric stabilizer. When small amounts of an anhydride functionalized polyolefin and an amine terminated polydiene were included, the asphalt polymers coupled to the emulsion interface where they acted as effective elastic barriers against coalescence. The in situ stabilized systems showed long-term storage stability at elevated temperatures.;Changes in the particle size distribution for a model polyethylene-asphalt emulsion indicated that failure starts through both Brownian and gravity-induced coalescence, much later followed by creaming caused by the density difference in the two phases. |
