Thermomechanical properties of liquid‐crystalline epoxy networks arranged by a magnetic field

Abstract

During the curing process of a liquid-crystalline epoxy resin, a relatively strong magnetic field was applied, and the thermomechanical properties of the cured resin were investigated. The network orientation and mechanical properties of the cured system were evaluated with wide-angle X-ray diffraction, dynamic mechanical analysis, and fracture toughness testing. The cured system was found to have an anisotropic network structure, which arranged along the applied field, and the anisotropy was reflected in the thermomechanical properties. In particular, the fracture toughness of the system dramatically increased when the network chains were arranged across the direction of the crack propagation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 758 -765, 2004

Liquid‐crystalline epoxy thermosets as matrices for ordered nanocomposites—a summary of experimental studies

“…The magnetic induction of about 1.8T enabled obtaining a monodomain structure in a single case. This result was particularly interesting, considering that similar results obtained by other authors required much stronger fields of about 10T . In the article it was also shown that the elastic modulus for structures oriented in a magnetic field increased from 10 9 to 10 10 Pa at temperatures of the order of −40°C.…”

The influence of a magnetic field on the morphology and thermomechanical properties of a liquid crystalline epoxy carbon composite

“…The calculation was based on the Eq. : where h w is the width at the half‐height of the maximum of scattering peak at the azimuth angle position in degrees. The determined values of the parameter f are listed in Table .…”

Liquid crystalline polymer networks based on a nematic epoxy resin with azoxy group

“…It was also reported that the type of the domain struc− ture (nematic, smectic) as well as the size of the domains de− pend directly on the temperature applied to the mixture dur− ing the curing reaction [9]. Moreover it was also possible to prepare a monodomain network, a state of which is macro− scopically anisotropic [7][8][9]. External magnetic or electric field (as well as preparation of the cell surface) applied dur− ing the curing process may result in an ordered matrix because monomers in the nematic phase are easy to orientate (the viscosity of the monomer is much lower than in the polymer) [10,11].…”

“…This results in different topo− logy of the same system, depending on the curing condi− tions. The same mixture can create an amorphous structure, i.e., the state of no arrangement, but it can also create a polydomain structure, which has many locally ordered areas [7][8][9]. It was also reported that the type of the domain struc− ture (nematic, smectic) as well as the size of the domains de− pend directly on the temperature applied to the mixture dur− ing the curing reaction [9].…”