Structure of glassy polymers. VII. Small‐angle X‐ray scattering from epoxy resins

Abstract

SynopsisThe small-angle x-ray scattering (SAXS) from an Epon 812 and two Epon 828 (one amine-cured and one anhydride-cured) epoxy resins has been measured using a Bonse-Hart system. The data cover the angular range (219) between 20 sec and 60 min. After correction for absorption, background and vertical beam divergence, they have been placed on an absolute basis by comparison with the scattering from a previously studied polycarbonate sample. The corrected absolute intensity decreases strongly with increasing angle between 20 sec and 2 min, decreases more gradually between 2 and 20-30 min, and reaches a nearly constant asymptotic value at larger angles. The magnitude of the intensity in the constant-intensity region is close to the value predicted by thermodynamic fluctuation theory for fluids applied at the glass transition temperature. The increase in intensity a t angles smaller than 20-30 min is associated with heterogeneities in the cured resins. These heterogeneities cover a range of sizes in all samples, from less than 100 8, to more than 1000 A, with the most frequently occurring size in the range 100-200 A.

Insights into Epoxy Network Nanostructural Heterogeneity Using AFM-IR

“…Whilst small angle neutron or x-ray scattering studies can be found to support resin heterogeneity, the link between nanoscale morphological features and chemical heterogeneity has not been established. 34,35 were bar coated in the same manner from 5 % w/w solutions in toluene (Fisher Scientific, >99%) and then cryogenically fractured prior to analysis.…”

Structural analysis of cured phenolic resins using complementary small-angle neutron and X-ray scattering and scanning electron microscopy

“…However, there are only a few SANS and SAXS studies addressing the nodular structures as compared to the number of SEM and TEM studies on the inhomogeneity. 2,[13][14][15] Du sek et al reported that the nodular structure is not an inherent property of cured epoxy resins because (i) both SEM images of fracture surfaces and SAXS curves of cured epoxy resins did not differ in principle from those of amorphous PMMA and PSt and (ii) swollen epoxy resins in tetrahydrofuran (THF) did not lead to an increase in the SAXS intensity corresponding to the particle size of 10-100 nm. 2,13 Matyi et al reported that SAXS results for epoxy resins indicated the presence of an inhomogeneity that is not associated with the nodular structure but with voids having a size distribution range larger than 10-100 nm.…”

“…2,13 Matyi et al reported that SAXS results for epoxy resins indicated the presence of an inhomogeneity that is not associated with the nodular structure but with voids having a size distribution range larger than 10-100 nm. 14 Bai reported that SANS results for epoxy resins indicated the absence of inhomogeneity of the cross-links in the range of 3-40 nm. 15 Tapping-mode atomic force microscopy (AFM) observations have also been reported in order to understand the cross-link inhomogeneity of epoxy resins through investigation of the hard and soft phases of the surface.…”

Molecular network development and evolution of nanoscale morphology in an epoxy‐amine thermoset polymer

“…Additional evidence for a nonhomogeneous network structure has been cited from dynamic mechanical analysis, swelling behavior and small angle X-ray scattering. [31][32][33] This work provides further evidence as to the nonhomogeneity of cured epoxy-amine systems by monitoring the development of the nonhomogeneous network architecture through the early stages of cure up to the onset of vitrification.…”