Efficient Isolation of Eucommia ulmoides Rubber for the Fabrication of Composite Film Materials with Better Mechanical Properties and Electromagnetic Interference Shielding Properties

Eucommia ulmoides rubber (EUR) is the ideal natural rubber resource in the field of rubber composite film materials due to the characteristics of lightweight, good sealing, etc. However, the traditional separation processes of EUR are complex and the yield of EUR is low. Additionally, EUR is very easily oxidized to a white, brittle, degradable powder, which limits the development and application of EUR products. In this study, the DES-H2O2 pretreatment synergistic enzymatic hydrolysis procedure was performed to reduce the "biomass recalcitrance" of E. ulmoides Oliver bark and result in a high yield EUR (88.38%). Furthermore, the isolated EUR was further blended with incompletely esterified lignin and carbon nanotubes (CNTs) to produce EUR-based composite membrane materials. The composite film materials showed good antioxidant and mechanical properties, and they had a mechanical strength of about 20.55 MPa after 60 days in the air environment. The prepared composite film material has certain electromagnetic interference (EMI) shielding properties, and the EMI shielding efficiency was 15.1 dB in the X-band. Meanwhile, the film exhibited excellent ultraviolet (UV)-shielding properties. This work presents a comprehensive and efficient process to achieve the utilization of E. ulmoides Oliver bark biomass resources and prepares EUR-based composite film materials with antioxidant and EMI properties.