| High molecular weight polymers can suppress the breakup of low-viscosity liquids by increasing the elasticity, particularly the extensional viscosity of the system. Recently, polyisobutylene (PIB) and polyethylene oxide (PEO) have been successfully applied as mist control agents for straight oil (PIB) and oil-in-water emulsion types machining fluids (PEO). However, the high shear stresses experienced in metal-working operations cause mechanical degradation of high molecular weight polymers. This necessitates periodic additions of fresh polymer to sustain effective control of misting. One solution to this problem is the development of self-associative polymer and polymer-surfactant systems that achieve the rheological effects of high molecular weight linear polymers that exhibit improved antimisting effectiveness at low concentrations, and improved shear stability due to structure regeneration.; First, laboratory atomization experiments are performed to show that the antimisting effectiveness of PEO is greatly enhanced by interactions between PEO and certain surfactants. Actually, the effectiveness of PEO-surfactant association depends on the surfactant chemistry. Sodium dodecyl benzyl sulfonate (SDBS) exhibits a strong structure-forming interaction with PEO, leading to excellent rheological properties for mist suppression, while sodium dodecyl sulfate (SDS) interactions with PEO have less influence on rheology and drop size. Atomization, shear and elongational viscometry, as well as dynamic light scattering and conductivity experiments are employed to probe the effects of these interactions on the drop size, rheology and structure of these systems.; Second, self-association behavior of a triblock copolymer of polystyrene-polybutadiene-polystyrene in a selective solvent system, heptane and toluene, is investigated. Shear viscosity measurements revealed the formation of associative structures as the copolymer concentration increases in the more selective solvent. However, atomization experiments did not show any increase in aerosol drop size although elongational viscosity measurements confirmed the copolymer's substantial contribution to the elasticity of the system. Thus, the mechanism for suppression of liquid breakup due to viscoelasticity is absent in these fluids. |
