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New approaches to reversible crosslinking in epoxy resins

1989; Wiley; Volume: 25; Issue: 1 Linguagem: Inglês

10.1002/masy.19890250108

0258-0322

Giuliana C. Tesoro, Vinod R. Sastri,

Photopolymerization techniques and applications

Abstract The objective of the research is to investigate epoxy resins where crosslinks formed in curing reactions can be cleaved and reformed without significant sacrifice in resin properties. Experimental disulfide‐containing crosslinking agents have been selected for the study, including dihydrazides of dithiodicarboxylic acids (aliphatic and aromatic) and dithioaromatic diamines. Conditions for curing reactions and for subsequent cleavage of crosslinks by reduction have been determined in model systems and confirmed for a prototype epoxy resin. A comparative evaluation of cure kinetics, crosslink density, and thermal and mechanical properties has been carried out for resin cured with aromatic curing agents (dithiodianiline and methylenedianiline) and with aliphatic compounds (3, 3′‐dithiopropionic acid dihydrazide and hexamethylenediamine). It has been shown that in resin fully cured with disulfide‐containing crosslinking agents, crosslinks are ruptured by reduction, and re‐established by oxidation under mild conditions, or by reaction of thiol groups with bifunctional alkylating agents.