Cleavable epoxy resins: Design for disassembly of a thermoset

Hexahydro-s-triazine: A Trial for Acid-Degradable Epoxy Resins with High Performance

“…In Figure 1B, similar peaks to those in Figure 1A appeared between 5.11 and 7.69 ppm belonging to HT ring and benzene ring, only two peaks corresponding to methylene derived from ethylenediamine replaced the peaks from −OCH 2 CH 3 of R1. Figures 2A and 2B are the 13 C NMR spectra of R1 and HT-A, respectively. All the peaks match well with the carbons of R1 and HT-A.…”

Thermally Self-Healing Polymeric Materials: The Next Step to Recycling Thermoset Polymers?

“…Besides the remendability, a breakthrough has been made here in terms of full recyclability and reworkability of this system. Nowadays, recycling of thermosetting materials at the end of the life cycle is often considered to be difficult and remains an unresolved issue. − The recycling techniques in current polymer recycling industries mainly involve mechanical (the use of grinding techniques to comminute thermoset recyclates as reinforcing fillers in new composites) and thermal processing steps (the use of heat to break the scarp composites down to recover the energy and feedstock), but they do not represent convenient choices from the economic and environmental point of view. − In contrast, our system can provide a feasible way to resolve the recycling issues of thermosetting polymers.…”

Reworkable Epoxies: Thermosets with Thermally Cleavable Groups for Controlled Network Breakdown

“…In addition, the presence of base interferes with the autocatalytic thermal cleavage of esters by liberated protons. Following established curing procedures, 9 hexahydro-4-methylphthalic anhydride (HHMPA) and excess epoxide were mixed in a 0.87:1 mole ratio to avoid side reactions, such as etherification. By design, the epoxies have weak, acid-labile ester linkages between two epoxy functional groups, so it is important to lessen side reactions which may introduce acid groups that can cleave the secondary or tertiary ester bonds before the epoxy is fully cured.…”

“…Curing Reactions. The diepoxides were cured with either hexahydro-4-methylphthalic anhydride (HHMPA) or cis -1,2-cyclohexanedicarboxylic anhydride (HHPA) as hardener, ethylene glycol as initiator, and benzyldimethylamine (BDMA) as catalyst . Samples used for TGA measurement were cured on a digital hotplate at 100 °C for 1 h and then at 145 °C (160 °C for ERL-4221) for 2−3 h. Samples for DMA and DMS measurements were degassed in the mold under vacuum at room temperature, precured at 90−100 °C for 1 h and then cured at 140−145 °C for 4 h (160 °C for ERL-4221) not in a vacuum, and then cooled slowly.…”