Structure, Viscoelastic Properties and Damping Mechanisms of Reactive Butadiene-nitrile Rubber/Epoxy Polymer Blends

Abstract

Carboxyl-terminated butadiene acrylonitrile (CTBN) rubber/ epoxy (diglycidyl ether of bisphenol-A) / diamino diphenyl methane polymer blends with 60 wt% of CTBN were formulated to evaluate the viscoelasticity and the damping properties. When the blend resins had micro-phase separated morphologies composed of epoxy-rich dispersed phases larger than 500 nm in diameter surrounded by a rubber-rich continuous phase, the loss factors (η) of the steel laminates adhered with the resin significantly depended on the environmental temperature and the resonant frequencies. The resins with epoxy-rich phases smaller than 200 nm in diameter had broad glass-transition temperature range that resulted in the high loss factor (η > 0.1) of the steel laminates in the broad temperature range. Inhomogeneous nano-gel structures with 20∼30 nm sizes were observed in more compatible resins by scanning probe microscopy, although appreciable micro-phase separation was detected by none of SEM and TEM. Pulse NMR suggested that the fraction of interfacial phase in the resins increased with increasing the compatibility of the blends. The large interfacial phase in the inhomogeneous nano-gel structures seems to play an important role in the damping mechanisms.

Interfacial control and mechanical properties of carbon black‐reinforced carboxyl‐terminated butadiene acrylonitrile rubber/epoxy polymer composites

“…The matrix polymer showed a wide glass transition region, ranging from below −30°C to over 100°C. These results demonstrate the heterogeneity of the matrix polymer, as was also observed in our previous work using dynamic mechanical analyses and scanning probe microscopy . In the tan δ curve for the matrix polymer, two peaks are present at approximately 0°C and 40°C, corresponding to CTBN‐rich and epoxy‐rich portions in the blend, respectively.…”

“…Our group has previously studied polymer blends consisting of a liquid reactive rubber (carboxyl‐terminated butadiene acrylonitrile rubber (CTBN)), an epoxy resin (diglycidyl ether of bisphenol‐A (DGEBA)), and an aromatic diamine (diamino diphenyl methane (DDM)) . Although CTBN is known to act as a toughening modifier in epoxy resins, in our prior work, it was used as the major component (at 60 wt%) of the polymer blends . All the components (liquid rubber, epoxy oligomer, and diamine) were found to react with one another to generate a covalent bonded network, and so the product was not technically an IPN.…”