Functional nano fillers in epoxy-dicyandiamide adhesives for prolonged shelf life and efficient cure

in e-Polymers (2011), (10), 1-15

Shelf life at room temperature and curing behaviour at elevated temperature are studied for hot-curing accelerated epoxies (EP, diglycidylether of bisphenol A plus dicyandiamide (Dicy)) by FTIR ... [more ▼]

Shelf life at room temperature and curing behaviour at elevated temperature are studied for hot-curing accelerated epoxies (EP, diglycidylether of bisphenol A plus dicyandiamide (Dicy)) by FTIR-spectroscopy and modulated DSC. The accelerator is added either directly or with nano-zeolite filler to the EP. Due to the immobilization of the accelerator in the pores of the nano-zeolite, the shelf life of this EP is 5 times longer than for the EP containing free accelerator. While the free accelerator acts during the whole heating step to curing temperature, the nano-zeolite does not release the accelerator before ca. 100 °C. As monitored by light microscopy, the released accelerator not only supports the curing but also stimulates the dissolution of the solid Dicy. As the result, network formation at 170 °C finishes within less than 25 minutes for the nano-filled EP. [less ▲]

Trans-Interfacial Polymerization and Matter Transport Processes in Epoxy-Alumina Nanocomposites Visualized By Scanning Brillouin Microscopy

in Journal of Physical Chemistry B (2010), 114(25), 8396-8404

The structural developments in the vicinity of the interface between the reactants of an epoxy are investigated using time- and space-resolved scanning Brillouin microscopy. The hypersonic profile across ... [more ▼]

The structural developments in the vicinity of the interface between the reactants of an epoxy are investigated using time- and space-resolved scanning Brillouin microscopy. The hypersonic profile across the phase boundary evolves with strong spatial asymmetry and exhibits erratic behavior within the resin-rich region, which is attributed to a complex interplay between matter transport, dissolution, polymerization, and molecular unravelling process. The presence of alumina nanoparticles in the resin changes the character of these matter transport and reaction processes significantly. On the one hand, the nanoparticles act as transport barriers, hindering the mixing of the reactive components; on the other hand they seem to have a catalytic influence on the epoxy polymerization under certain circumstances. Their transport against gravity is tentatively attributed to gradients in surface tension. [less ▲]

Different glassy states, as indicated by a violation of the generalized Cauchy relation.

in New Journal of Physics (2003), 5(80), 1-11

Using Brillouin spectroscopy as a probe for high-frequency clamped acoustic properties, a shear modulus can be measured in addition to the longitudinal modulus already well above the thermal glass ... [more ▼]

Using Brillouin spectroscopy as a probe for high-frequency clamped acoustic properties, a shear modulus can be measured in addition to the longitudinal modulus already well above the thermal glass transition. On slow cooling of the liquid through the thermal glass transition temperature Tg, both moduli show a kink-like behaviour and the function follows a generalized Cauchy relation (gCR) defined by the linear relation , which completely hides the glass transition. In this work we show experimentally that on fast cooling this linear transformation becomes violated within the glassy state, but that thermal ageing drives the elastic coefficients towards the gCR, i.e. towards a unique glassy state. [less ▲]