Air Force

Multi-functional crosslinking agent

Material comprises several anhydride functional groups to bond with heat-resistant shape-memory polymers

Materials

Air Force scientists have developed a covalent network structure to improve shape-memory effects at high temperatures. The patented technology is available via license agreement to companies that would make, use, or sell it commercially.

Shape-memory materials are used across diverse industries, including medical and dental applications. (Daniel Frank/Pexels)

Shape-memory materials, such as shape-memory alloys (SMAs) and shape memory polymers (SMPs), have been widely used in actuation, aircraft, robotics, piping, medical, and dental applications. SMPs are a class of active materials that can be programmed to assume a temporary shape or a series of temporary shapes and later return to a memorized permanent shape established by a covalent or physical network through applying thermal, electrical, or other environmental stimuli.

SMPs have significant advantages over SMAs, including a higher capacity for elastic deformation (up to 200% in most cases), lower cost, lower density, a broader range of application temperatures, comparatively easy processing, and potential biocompatibility and biodegradability. Unfortunately, the current SMPs consist of high-alkyl content polymers such as polyurethane which lack shape-memory properties and thermo-oxidative stability at temperatures above 150° C.

Several high-temperature SMPs have recently been developed, such as aromatic polyimides, and crosslinked with multifunctional amine crosslinking agents to impart shape-memory effects. However, the multifunctional amine crosslinking agents are limited to polymers bearing amine-reactive groups.

Air Force researchers have addressed this pressing need for new multifunctional crosslinking agents to impart shape-memory effects to the parent polymers. This innovative multi-anhydride crosslinking agent is suitable to crosslink polyimide, polyamide, and poly(amide-imide) polymers. These crosslinking agents have three or four anhydride functional groups and can cause shape-memory effects to heat-resistant polymers to create a covalent network structure that results in shape memory effects at elevated temperatures.

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