Hot melt processing strategy to modify eucommia ulmoides gum by click reaction

Abstract

AbstractUnder the condition of hot melt processing, the modification of eucommia ulmoides gum (EUG) by mercapto compounds, n‐Octyl mercaptan (OM), and isooctyl mercaptoacetate (IOMA) was realized by the click reaction of thiol‐ene. The 1H‐NMR results confirmed that the grafting rate of mercapto compounds was 2.28%–5.30% and 1.68%–3.85% when OM and IOMA reacted with EUG in thiol‐ene click reaction under hot melt processing conditions. The DSC results showed that the crystallinity of EUG‐OM was higher than that of EUG when the amount of grafted compound OM ranged from 0.86 to 1.39 mol%. When IOMA‐modified EUG products change from partially crystalline to amorphous, the critical value of IOMA is 2.15 mol%. With the grafting rate of mercapto compounds increasing, T10, T50, and T90 of mercapto modified EUG has decreased to some extent, the ML, MH, and the difference of MH and ML also decrease at the same time. Compared with unmodified EUG vulcanizate, the hardness and tensile strength of a mercapto compound modified EUG vulcanizate decrease, while the elongation at break significantly increases. The stress‐strain curve of a mercapto compound modified EUG vulcanizate confirmed the transition from rigid crystalline materials to elastomers. This property change should be attributed to the plasticizing effect caused by the crystallization property of the modified EUG. The chemical modification of EUG under solvent‐free conditions is environmentally friendly, and the product is uniform, which may be of great significance for practical industrialization.