Extensional Rheology & Analytics of Material Characterization
Extensional flows are important to converging and squeezing flows that occur in polymer processing operations such as injection molding, extrusion, blow molding, film blowing and calendering. Uniaxial extensional flow measurement is particularly useful in polymer characterization because it is the ’strongest‘ flow field one can generate with respect to both polymer chain stretch and molecular alignment, making it highly sensitive to polymer molecular structure and architecture. Although uniaxial extension experiments were once difficult to perform, recent development have made these experiments simple to conduct using accessories that adapt rotational shear rheometers to perform uniaxial extension. In addition to elucidating macrostructural features such as molecular weight, molecular weight distribution, and polymer long-chain branching, when coupled with in-situ supplemental experimental techniques such as flow birefringence and image analysis, extensional rheology can be used to gain valuable fundamental insight into flow induced crystallization of polymers during extension and localized flow phenomena. Specific examples of extensional rheology and flow-induced crystallization will be presented for two materials: butyl elastomer and linear polyethylene.
ABOUT THE SPEAKER
Dr. Sentmanat received his B.S. (1990) in Mechanical Engineering from Texas A&M University in College Station, TX, and then headed north to Montreal, Canada where he received his M.Eng. (1992) and Ph.D. (1995) in Chemical Engineering from McGill University under the supervision of Prof. John M. Dealy. Dr. Sentmanat began working as a Senior Research Physicist at The Goodyear Tire & Rubber Company at Corporate Research in Akron, OH in 1995. After authoring more than two dozen worldwide patents he left Goodyear at the end of 2003 to found Xpansion Instruments, exclusive manufacturer of his invention, the SER Universal Testing Platform, which has served to redefine the paradigm in experimental extensional rheology and miniature-scale materials testing. Based now in the Austin, TX area, Dr. Sentmanat also serves as the President of Polymer Consulting Group, a firm that has catered to the polymer, biomedical, oil & gas, and scientific legal communities since 2003.