Polymer Engineering Center > Research > Sensors For Polymer Processing

Sensors play a crucial role in process monitoring, closed-loop control, and property measurement in polymer processing. In this study, we plan to develop a new type of sensors, based on electrostriction, for monitoring polymer processing and product performance. Electrostriction, deformation induced anisotropy in dielectric properties, is the dielectric counterpart of optical-mechanical effect which manifests as birefringence. Unlike their optical counterparts, however, dielectric measurements are applicable to all dielectric materials regardless of their optical transparency. We are working on electrostriction sensors aimed at performing on-line and post-molding measurement of stress field distribution inside injection-molded parts. In contrast with traditional methods, such as optical sensors and direct strain gage measurements, our approach not only eliminates the requirements of mold/sample transparency and direct mechanical contact but also targets unprecedented on-line stress measurement. We are also working on direct and non-destructive quantifying fiber orientation and concentration distribution in polymer composites. This can be done by measuring the in-plane anisotropy of dielectric properties using a novel fringe-field capacitor sensor design. We also plan to use the new sensor to investigate important process behavior of other polymer processing methods. These include control of uniformity and thickness of coating layers, the material slippage in blow molding and thermoforming applications as well as the onset of melt fracture during extrusion. In addition to developing the scientific background for the new sensors, we are working to incorporate the existing sensor capabilities with an ultimate goal to develop fully integrated sensor systems fabricated with micro-machining and photolithography technologies. Successful completion of this research will offer a new dimension for commercial sensor applications and boost product quality and production efficiency with more insightful polymer processing. This proposed research has a high potential of benefiting industrial and economic development in both the near and long terms. By the end of the project, we expect to develop a new sensor approach based on measurements of dielectric anisotropy in materials. We will apply these sensors solution to control process induced stresses and fiber orientation in polymers. Anticipated benefits: New commercial sensor applications for a wide variety of polymer processing methods to boost product quality and production efficiency. Unprecedented measurement of molded-in residual stresses and effective measurement of orientation and distribution of reinforcing fibers and fillers. The Polymer Engineering Center has numerous dynamics mechanical testing instruments with loading capacities ranging from 10-4 to 106 N. The picture shows operation of state-of-the-art Dynamic Mechanical Analyzer DMA 2980 from TA Instruments.