Evaluation of viscoelastic materials: The study of nanosphere embedment into polymer surfaces and rheology of simple glass formers using a compliant rheometer

Date

2008-08

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Publisher

Texas Tech University

Abstract

Viscoelasticity is a fundamental property of many materials such as polymers, inorganic glasses, biological materials, small molecule glass formers, and composites. This fundamental property is what links the research presented here. There are two focuses that will be presented: 1. A background of nanoparticle is presented and a viscoelastic model is applied to determined the actual rheological behavior of materials. An atomic force microscope (AFM) is used to measure the embedment depth as nanoparticles are pulled into the surface by the thermodynamic work of adhesion. 2. Instrument compliance effects caused by both the transducer and entire instrument itself can induce large errors on shear measurements of viscoelastic properties of materials. Examples of instrument compliance effects on the measurement of the material properties of small molecular glass formers and a commercially available polydimethysiloxane (PDMS) rubber using a commercial rheometer are presented. A technique is presented and applied to correct for compliance effects in stress relaxation experiments and dynamic frequency sweep experiments. Recommendations are made for both experimental and instrument design to avoid and/or minimize compliance effects.

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