Resistance to Cleavage of Core⁻Shell Rubber/Epoxy Composite Foam Adhesive under Impact Wedge⁻Peel Condition for Automobile Structural Adhesive

• Published in: Polymers Vol. 11; no. 1; p. 152
• Main Authors: Back, Jong-Ho, Baek, Dooyoung, Shin, Jae-Ho, Jang, Seong-Wook, Kim, Hyun-Joong, Kim, Jong-Hak, Song, Hong-Kyu, Hwang, Jong-Won, Yoo, Min-Jae
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 17.01.2019; MDPI
• Subjects: Adhesives; automobile structural adhesives; Cleavage; Computed tomography; core–shell rubber; Curing; Dimensional analysis; epoxy composite foam adhesive; Epoxy resins; Foaming agents; Heat; Impact resistance; Impact tests; impact wedge–peel test; Investigations; Peel tests; Pore size; Rubber; Standard deviation; Steric hindrance; Three dimensional imaging; Weight reduction; Belgium; Germany; automobile structural adhesives; impact wedge–peel test; epoxy composite foam adhesive; core–shell rubber
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym11010152

Epoxy foam adhesives are widely used for weight reduction, watertight property, and mechanical reinforcement effects. However, epoxy foam adhesives have poor impact resistance at higher expansion ratios. Hence, we prepared an epoxy composite foam adhesive with core⁻shell rubber (CSR) particles to improve the impact resistance and applied it to automotive structural adhesives. The curing behavior and pore structure were characterized by differential scanning calorimetry (DSC) and X-ray computed tomography (CT), respectively, and impact wedge⁻peel tests were conducted to quantitatively evaluate the resistance to cleavage of the CSR/epoxy composite foam adhesives under impact. At 5 and 10 phr CSR contents, the pore size and expansion ratio increased sufficiently due to the decrease in curing rate. However, at 20 phr CSR content, the pore size decreased, which might be due to the steric hindrance effect of the CSR particles. Notably, at 0 and 0.1 phr foaming agent contents, the resistance to cleavage of the adhesives under the impact wedge⁻peel condition significantly improved with increasing CSR content. Thus, the CSR/epoxy composite foam adhesive containing 0.1 phr foaming agent and 20 phr CSR particles showed high impact resistance ( = 34,000 mJ/cm²) and sufficient expansion ratio (~148%).