Preparation And Properties Of Eucommia Ulmoides Gum Based

Eucommia ulmoides gum(EUG)is a kind of natural polymer material with good biocompatibility,excellent rubber-plastic duality,and good mechanical properties,which has attracted much attention in the field of novel biomaterials in recent years.Meanwhile,the development of wearable electronic products has promoted the wide application of flexible electronic composites.EUG has become a new candidate in the field of wearable conductive films by virtue of its excellent properties.In this paper,EUG was firstly extracted from Eucommia seed bark and subsequently modified by emulsion method to obtain epoxidized Eucommia ulmoides gum(EEUG).Subsequently,EUG and EEUG were compounded with traditional conductive polymer polyaniline(PANI)and newly inorganic conductive filler liquid metal(LM),respectively.Then,this composite was casted into a film to prepare conductive and elasic films.The main contents are as follows.Firstly,EUG was extracted from Eucommia seed bark by sodium hydroxide/petroleum extraction method.After that,we prepared EEUG with different epoxy degree by emulsion method,respectively.The experimental results showed that,with the increase of reaction time and formic acid concentration,the epoxy degree gradually increased and the crystallinity of EEUG continuously decreased.When the epoxy degree was 20%,its melt peak disappeared on the DSC curve.Along with the increase of epoxy degree,the tensile strength decreased,while the elongation at break significantly increased to 1430%,indicating that the EEUG has the prospect of preparing soft elastic rubber.Secondly,the EUG was blended with PANI and the composite conductive films were prepared by solution casting.The results of scanning electron microscopy tests showed that PANI was mainly distributed in the rubber matrix in granular form because of its low compatibility with the rubber matrix.Differential scanning calorimetric analysis showed that the addition of PANI disrupted the crystallization of EUG.Tensile test results showed that the elongation at break and tensile strength of the composite films decreased(8.5% and 14.4 MPa).It shows that EUG is not compatible with PANI and cannot be directly used as PANI flexible device substrate.Further,we made the films by solution casting method with different epoxy degree of EEUG and PANI.We studied the electrical conductivity and mechanical properties of the composite films.Infrared spectra confirmed that the gelation phenomenon was mainly attributed to the formation of a large number of hydrogen bonds between the epoxy group and the amino group.The contact angle reached to 122° with hydrophobicity of the materials enhanced.As the epoxy degree increased,the tensile strength of the composites increased from 0.054 MPa to 11.5 MPa,while the elongation at break continuously increased to 107%.Compared with the EUG/PANI composite films,EEUG is expected to be used as a substrate for PANI-based flexible devices due to the introduction of epoxy groups that promote compatibility between PANI and substrate,resulting in superior mechanical properties.Finally,the conductive films compounded with EUG and micronanosized LM were prepared by ultrasonic mixing.Then,we investigated the electrical conductivity,mechanical and other properties of the films obtained from EUG and n-dodecyl mercaptan(NDM)stabilized LM.The experimental results showed that,compared with no dispersant,the NDM-dispersed LM was more stable and the particle size of LM droplets modified by NDM decreased apparently.The particle surface changed from a slightly wrinkled structure to smooth.Meanwhile,the experimental test results showed that the dispersant-stabilized LM droplets were more uniformly distributed in the EUG substrate,indicating that the addition of NDM helped to enhance the compatibility of liquid metal and EUG materials.The results of differential scanning calorimetric analysis showed that the addition of nanosized LM destroyed the crystalline structure of EUG.Moreover,the melting peak occured near-28?-10°C on the curves,which was the subcooling phenomenon caused by the nanosized LM.The addition of dispersant led to a significant increase in the tensile strength of the EUG/LM up to 38.11 MPa,but the change in elongation at break was relatively unconspicuous.The composite films could achieve rapid monitoring of motion capture,showing the prospect of wearable conductive films for human motion and other applications.