Reactivity, processability, and thermal stability of tetrafunctional glycidyl ether cyclic siloxane epoxy hybrid networks

• Published in: Journal of applied polymer science Vol. 141; no. 33
• Main Authors: Gan, Houlei, Seraji, Seyed Mohsen, Khan, Masihullah Jabarulla, Zhang, Juan, Swan, Samuel R., Senanayake, Rusheni Bhagya, Varley, Russell J.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 05.09.2024; Wiley Subscription Services, Inc
• Subjects: addition polymerization; Amines; Aromaticity; Benzene; Bisphenol A; Carbon fiber reinforced plastics; Chemical synthesis; Combustion; crosslinking; Diamines; Epoxy resins; Exothermic reactions; Fiber composites; flame retardance; Hardeners; Heat transfer; High temperature; Hydrosilylation; kinetics; Methylene dianiline; Miscibility; Phenylenediamine; Rate constants; Reaction kinetics; Siloxanes; Steric hindrance; Thermal resistance; Thermal stability; Toluene; viscosity and viscoelasticity
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.55849

A low viscosity tetra‐functional cyclosiloxane epoxy resins (TGTS) is synthesized via a one‐step hydrosilylation reaction and cured separately with four different aromatic diamines to explore the reaction kinetics, network development, and thermal resistance. The hardeners used are 1,3‐phenylenediamine (PDA), diethyl toluene diamine (DETDA), 4,4‐diaminodiphenylmethane (DDM), and 1,3‐bis(4‐aminophenoxy) benzene, because of their availability and aromaticity. During cure with TGTS they all display autocatalytic behavior, but when compared to a traditional organic epoxy resin, diglycidyl ether of bisphenol A (DGEBA) cured with DDM however, the rate constants are about 3 times slower and less exothermic. The DETDA hardener in particular exhibits significantly slower rates of cure when compared to the other amines, being about an order of magnitude slower compared to the PDA curative. This is attributed to higher steric hindrance, compounded by reduced miscibility. The TGTS‐DDM carbon fiber composite displays the most thermal resistance after extended exposure to 220°C, producing the least mass loss and after combustion of about 12% compared to 20% for the DGEBA cured with DDM. The results presented here, illustrate that a tetrafunctional cyclic siloxane epoxy resin, can exhibit excellent processability, evidenced by very low viscosities and long gelation times, whilst also displaying excellent thermal resistance, whether at elevated temperature, or during combustion. Cyclic siloxane epoxy resins cured with aromatic amines are highly processable yet durable at elevated temperature.