Effect of the crosslinking density and programming temperature on the shape fixity and shape recovery in epoxy–anhydride shape‐memory polymers

Abstract

In addition to the fabrication of thermoset epoxy–anhydride shape‐memory polymers (SMPs), a systematic experimental investigation was conducted to characterize the crosslinking density, micromorphology, thermal properties, mechanical properties, and shape‐memory effects in the epoxy SMP system, with a focus on the influence of the crosslinking density and programming temperature on the shape‐fixity and shape‐recovery behaviors of the polymers. On the basis of the crosslinking density information determined by NMR technology, we concluded that the effect of the crosslinking density on the shape‐fixity behaviors was dependent on the programming temperature. The advantage of a nice combination of crosslinking density and programming temperature provided an effective approach to tailor the actual shape recovery within a wide range. The increasing crosslinking density significantly improved the shape‐recovery ratio, which could be further improved through a decrease in the programming, whereas the crosslinking density was more fundamental. This exploration should play an important role in the fabrication and applications of SMP materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40559.

Review of Progress in Shape Memory Epoxies and Their Composites

“…Similar versatility exists also for anhydride cured EPs [ 20 ] albeit anhydrides were less frequently used compared to amine for EP curing [ 28 , 29 , 30 , 31 ]. The possible reason behind this fact is that the E g / E r ratio is much lower for anhydride-cured than for amine-cured version.…”

“…It is usually accepted that this ratio should be in the range of several hundred for a polymer to exhibit good SM properties. To overcome this problem long chain anhydrides [ 28 , 29 ] or aliphatic epoxies [ 30 ] are incorporated into the network to reduce its rigidity. A further tool of network flexibility is given by changing the stoichiometric ratio.…”

Improving of Mechanical and Shape-Memory Properties in Hyperbranched Epoxy Shape-Memory Polymers

“…This decreases the average chain length between netpoints and restricts the molecular mobility, which leads to an increase in T g . As can be observed in Table 2, an increase in Lupasol Ò also lowers and broadens the curve of tan d. The shape of the tan d curve can be correlated with its network structure: the higher and narrower the shape of the curve of tan d, the more homogeneous and mobile the network structure is [18]. The presence of Lupasol Ò leads to a more heterogeneous network structure due to the inherently disperse nature of the hyperbranched poly(ethyleneimine) and the presence of different types of crosslinks from the pre-existing tertiary amines and the reacted primary and secondary amines.…”

Rheological and Mechanical Characterization of Dual-Curing Thiol-Acrylate-Epoxy Thermosets for Advanced Applications

“…As expected, raising the proportion between thiol and acrylate results in lower T g s for the final materials because of the softening effect of the thiol-acrylate network. The shape of the tanδ peak during the material relaxation can be correlated with its network structure: the higher and narrower the peak of tanδ, the more homogeneous and mobile the network structure [26]. Similar values of FWHM around 11 °C were obtained with both thiol-epoxy and thiol-acrylate pure formulation since these networks were built with the same crosslinking functionality.…”