Moisture Effect in Composites and Structural Adhesives: A Fundamental Study of Underlying Mechanisms
Abstract
High temperature resistant epoxy resins are typically very polar materials and are capable of absorbing considerable quantities of water, typically 1 to 7% by weight. In addition to being very polar, the resulting glassy structures can also be extremely heterogeneous in terms of electron density as a result of the cure process being limited by diffusion. The focus of this work is to quantify this heterogeneous nature in terms of a nanopore content from positron annihilation lifetime spectroscopy (PALS), and then to use this nanoporosity to isolate the topological contributions to the transport process (how much water is absorbed and how fast) from the polar contributions. We demonstrate that if the polarity of the network is maintained constant, the nanopore content does not significantly influence the diffusion coefficient (how fast) but helps dictate the equilibrium moisture uptake (how much). specifically, it is shown that the ultimate weight gain depends upon the portion of nanopores that are static as opposed to dynamic in nature. Finally, a simple channel-like morphology of the nanopore structure is introduced to help depict the transport process.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 20, 1997
- Accession Number
- ADA338738
Entities
People
- Albert F. Yee
Organizations
- University of Michigan