The Polymer Processing Lab on a Chip
Friday, May 6, 2011 - 1:15pm - 2:30pm
The modern polymer processing laboratory typically contains disparate instruments for various operations such as rheometry, mixing, injection molding and interfacial tension measurement. Modification and customization of these instruments to meet the demands of a particular application is costly and time intensive. The required sample sizes for these operations ranges from (1 – 10^4) g. We propose to merge the multiple processing and rheology operations into a single platform that is inspired by microfluidics methods. We term the platform “Polymer Processing on a Chip” and describe here two key modes in which it can be used: rheometry and mixing. Advantages of this platform are the ability to structure blends, to work on independent samples in parallel, to ease the reconfiguration of flow geometry, and to work with small sample sizes (~50 mg).
The first mode that we have developed is melt and solution rheometry. Melt rheometry is essential to the polymers industry because it provides critical information regarding the processability of new materials and provides insights into a wide range of fundamental material properties. However, bulk rheological techniques are problematic in cases where material supply is limited, where large numbers of sample measurements are required and when rapid sample loading and cleaning procedures are needed. Two principle classes of rheometers have wide scale use in polymers research: capillary rheometers and rotational rheometers. These two classes of rheometers are thus not amenable to the high throughput approach being developed in many laboratories.
We call our rheological mode a Multi-sample Micro-slit Rheometer (MMR) – essentially a pressure-driven slit-rheometer. The use of pressure as the driving force allows for simple parallelization of the design as well as mechanical simplicity. The induced flow is measured by optically tracking the position of the flow front as the fluid fills the channel. In our current design, we require approximately 20 mL per sample and measure four samples simultaneously. The MMR offers the simplicity of capillary rheometry and a design that enables parallel measurements on limited quantity samples.
The second mode for the polymer processing on a chip is the melt mixing of immiscible polymers. Blending by melt mixing of immiscible polymers to create materials with superior properties is widely used in the polymer industry across multiple product lines. Significant research is devoted to development of new polymers, their blending strategy, the resulting structure and the ultimate properties. It is well known that specific structures can enhance application specific properties; for example, a multi-layer structure may be desired to reduce gas transport , a co-continuous structure may be desired for a polymer scaffold pre-cursor for tissue engineering and a domain/matrix structure is utilized to improve properties such as brittleness. There are two issues associated with the development of new immiscible blends materials that we address in the current work. The first is the difficulty in generating complex and targeted structures. The second is the frequent gap between the quantity of materials available during the development of new polymers and the quantity needed for typical laboratory scale mixers. In the present work, we present a new strategy – based on a planar polymer micro-mixer (PPMM) – to create targeted structures from immiscible polymers.
Host: Jeff Urbach