Effect of pore structure, mechanical performance, and operational temperature on damping behavior of thermal expandible rubber-based adhesives

Abstract

Adhesives exhibit multifaceted functionalities beyond adhesion as improving acoustic performance by reducing motion of parts, filling gaps, and facilitating homogeneous stress distribution. The expandable nature of certain adhesives allows them to absorb and dissipate energy effectively, which is beneficial in applications requiring impact resistance. The objectives of this study are acoustic performance measurement by utilizing Oberst and Frequency Response Function (FRF) methods to evaluate the damping capabilities of various rubber-based thermally expandable adhesive formulations; mechanical strength assessment by measuring the lap shear strength to determine the adhesives' performance under different operational temperatures; pore structure analysis using Scanning Electron Microscopy (SEM) to analyze pore morphology and to investigate its effects on acoustic performance. Differential Scanning Calorimetry (DSC) analysis was conducted to evaluate the thermal properties of rubber adhesive formulations. Glass transition temperatures were determined for the adhesives to understand behavior of damping during the Oberst and FRF tests. Pore structures, amounts, and distribution affected damping behavior of materials directly, but these properties did not cause a reduction on lap shear separtion strength. Operating temperatures and aging conditions affect damping behavior, Young modulus, and adhesion. Salt spray aging did not have significant effect on lap shear strength of rubber adhesive formulations.