SURFACE VISCOSITY OF POLYDIMETHYLSILOXANE MONOLAYERS.
Abstract
The surface viscosities of a series of polydimethylsiloxanes were studied using a canal viscometer as well as a torsional surface viscometer. The siloxane monolayers investigated had molecular weights ranging from 520 to approximately 105,000 and included both the ethoxy and trimethyl end-blocked polymers. The surface viscosity of even the highest molecular weight polydimethylsiloxane monolayer was extremely low, below the limit of sensitivity of the canal viscometer, which is of the order of 0.0001 surface poise. This surface viscosity is remarkably low when compared with monolayers of other polymeric materials that have been studied at the water/air interface. Many of these polymers such as poly-e-capramide (6-Nylon), the proteins, and synthetic polypeptides have given highly viscous, or viscoelastic, non-Newtonian films even at film pressures of only a few dynes/cm. The low surface viscosity of the siloxanes reflects the relatively low intermolecular cohesion that exists between adjacent siloxane chains in a monolayer. This low surface viscosity may in part explain the defoaming and antifoaming ability of the polydimethylsiloxane fluids. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 23, 1966
- Accession Number
- AD0643847
Entities
People
- N. L. Jarvis
Organizations
- United States Naval Research Laboratory