Effect of molecular weight between crosslinks on the fracture behavior of rubber-toughened epoxy adhesives

• Published in: Journal of applied polymer science Vol. 79; no. 1; pp. 38 - 48
• Main Authors: Kang, Byoung Un, Jho, Jae Young, Kim, Junkyung, Lee, Sang-Soo, Park, Min, Lim, Soonho, Choe, Chul Rim
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 03.01.2001; Wiley
• Subjects: Applied sciences; Exact sciences and technology; formulation; interfacial failure; Mechanical properties; Organic polymers; Physicochemistry of polymers; Properties and characterization; rubber agglomeration; rubber-toughened epoxy adhesive; Acrylic elastomer; Crosslink density; Morphology; Mechanical properties; Liquid rubber; Epoxy resin; Property structure relationship; Nitrile rubber; Experimental study; Adhesive; Fracture energy; Modified material
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/1097-4628(20010103)79:1<38::AID-APP50>3.0.CO;2-O

The effect of molecular weight between crosslinks, Mc, on the fracture behavior of rubber‐toughened epoxy adhesives was investigated and compared with the behavior of the bulk resins. In the liquid rubber‐toughened bulk system, fracture energy increased with increasing Mc. However, in the liquid rubber‐toughened adhesive system, with increasing Mc, the locus of joint fracture had a transition from cohesive failure, break in the bond layer, to interfacial failure, rupture of the bond layer from the surface of the substrate. Specimens fractured by cohesive failure exhibited larger fracture energies than those by interfacial failure. The occurrence of transition from cohesive to interfacial failure seemed to be caused by the increase in the ductility of matrix, the mismatch of elastic constant, and the agglomeration of rubber particles at the metal/epoxy interface. When core‐shell rubber, which did not agglomerate at the interface, was used as a toughening agent, fracture energy increased with Mc. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 38–48, 2001