Bio-based cyclized: Eucommia ulmoides gum elastomer for promising damping applications

Eucommia ulmoides gum (EUG) is an important bio-based material with a structure similar to that of natural rubber. However, EUG is a hard plastic at room temperature due to crystallization, which limits its wide application. In this paper, a bio-based cyclized Eucommia ulmoides gum (CEUG) elastomer with various degrees of cyclization was prepared using TiCl₄/CH₃COOH as catalysts. ¹H-NMR and FT-IR techniques were used to obtain structure information. It was found that di-, tri-, and tetra-substituted olefins in the cyclized sequence were formed during cyclization. DSC and XRD results indicated that the cyclized structure could inhibit crystallization. When the degree of cyclization reached 8.2%, crystallization disappeared and the material transformed from a plastic into an elastomer. With increasing of the degree of cyclization, the glass transition temperature (T_g) of CEUG increased and the thermal stability was enhanced, but the molecular weight decreased significantly. Above all, DMA results showed that the tan δ_max could reach 1.2 when the degree of cyclization was 20.0%, and the damping temperature range could be adjusted by controlling the degree of cyclization. This new elastomer is expected to contribute to the development of damping materials.