1. Kinetic Control of Epoxy Morphology
Changhua Liu and Elliot P. Douglas
University of Florida, Department of Materials Science and engineering, Gainesville, FLN
Epoxy resins are a versatile class of thermosetting polymer, which are extensively used as composite matrix and structural adhesive. A lot of evidence shows that there are nano-scale microstructures due to crosslink density variation in cured epoxy resins. Both fracture toughness and water diffusion coefficient have been shown to correlate with the microstructure of epoxy resin. We have found that changes in curing history and epoxy formulation will lead to differences in the size and distribution of crosslink density variation.
25 % excess epoxy
Hardener with much lower reactivity
Lower curing T
It is our goal to develop a model to predict such heterogeneity as a guide for processing and formulation applications and thus we need to quantitatively analyze the heterogeneity. AFM phase images were our main tool.
In a phase image, the dissipated energy Edis due to tip-sample interaction can be calculated on each pixel, which is roughly proportional to the viscosity of the sample on that pixel.
Between samples, the approach-phase-distance (APD) curves of an array of pixels was used to reconstruct tip-sample interaction forces so that phase values can be mapped to materials properties using DMT model.
Current experiment result; improvement in progress
Reconstruction from simulated data;
Near ideal case