This grant provides for the acquisition of a Rheometrics Scientific Melt Elongational Rheometer (RME) and a Rheometrics Scientific Advanced Rheological Expansion System (ARES). Both instruments are needed for investigating complex Fluid dynamics in bulk liquids and near solid surfaces. The RME is the only commercial rheometer available for studying extensional flow behavior of polymer melts, while the ARES rheometer is the only research-grade commercial instrument that allows simultaneous, time-dependent measurements of shear and normal stresses in polymer liquids. The proposed instruments will be the first of their kind at Texas A&M University, and will be used in four research projects and for class room demonstrations in two graduate-level polymer engineering courses. In one project (DMR-9816105), the RME and ARES rheometers will be used to determine the fundamental origin of strain hardening and apparent extension thickening behavior of branched polymers and their blends with chemically identical linear polymers. This research will be facilitated by a series of novel An-A-An and An-A(A)m-An multi-arm polybutadienes synthesized by the principal Investigator and a collaborator. These polymers are believed, on theoretical grounds, to capture the essence of commercially important branched polyolefins and will shed new light on the effect of polymer architecture on relaxation dynamics and rheological behavior in extensional and shearing flows. In another research project (CMS-9713372), the ARES rheometer will be used to perfect a new superimposed step/steady shear flow technique recently developed by the principal investigator and his students for isolating dynamics of polymer contour length stretch in shear flows. In the third project (CTS-9624254), a two-step grafting procedure will be used to sequentially graft polymers and low molecular weight chlorosilanes to the ARES rheometer platens. The surface modified rheometer platens will then be used in standard shear rheological testing of bulk, chemically identical polymers to investigate momentum transport, frictional drag, wall slip, and relaxation dynamics of polymers near surfaces. Results from this study will provide the first rigorous test of a scaling theory developed by the principal investigator and his students for quantifying polymer friction, slip, and dynamics near solid surfaces. %%% This grant provides for the purchase of a Rheometrics Scientific Melt Elongational Rheometer (RME) and a Rheometrics Scientific Advanced Rheological Expansion System (ARES). Both instruments are needed for investigating polymer properties in bulk liquids and near solid surfaces. The RME is the only commercial rheometer available for studying extensional flow properties of polymer melts, while the ARES rheometer is the only research-grade commercial instrument that allows measurements of multiple components of stress in polymer liquids. The proposed instruments will be the first of their kind at Texas A&M University, and will be used in four research projects and for class room demonstrations in two graduate-level polymer engineering courses. Three of the four projects are National Science Foundation sponsored activities related to development of structure-processing relationships in plastic materials and for polymer surface coatings. The polymer engineering courses introduce students to polymer physics and polymer rheology.
