Mechanical and Sound Absorption Properties of EUG / CIIR Vulcanized With Phenol‐Formaldehyde Resin

Abstract

ABSTRACT Eucommia ulmoides gum (EUG) was incorporated into chlorinated isobutylene isoprene rubber (CIIR) and vulcanized using phenol‐formaldehyde (PF) resin and/or sulfur to produce EUG/CIIR rubber blend with various EUG contents. The mechanical properties, damping behavior, and sound absorption performance of the blends were evaluated. The results showed that the blends vulcanized by a dual‐curing system composed of phenol formaldehyde resin (5% of CIIR weight) and sulfur exhibit superior mechanical and sound absorption performances. With increasing EUG content, the tensile strength, hardness, and rebound resilience increased. The blends consisting of CIIR/EUG (80/20 w/w) show a maximum elongation at break of 1137% and a sound absorption coefficient of 0.72. Dynamic mechanical analysis indicated that the damping peak decreased gradually with increasing EUG content, and sound absorption demonstrated a maximum at 20% EUG. SEM and DSC measurements revealed that a sea‐island morphology is present in blends at 10 ~ 20% EUG, in which EUG microcrystallites were dispersed uniformly in the CIIR phase; phase separation occurred while the EUG content is 50%, accompanied by a sharp decrease of sound absorption, suggesting that uniformly dispersed EUG microcrystallite domains can enhance sound absorption, probably as a result of multiple reflections of sound waves within crystalline regions and scattering between the EUG/CIIR interface.