Structure property relationships of biobased n-alkyl bisferulate epoxy resins
Résumé
In this work, a series of bio-based chemically recyclable epoxy resins were synthesized from n-alkyl bis-ferulate esters that do not activate human estrogen receptor alpha (ERa). Viscosities of corresponding glycidyl ether n-alkyl bisferulate resins, determined by steady shear rheology, range from 12-9.4 Pa s. Activation energies of flow range from 83-96 kJ mol(-1) and are similar to the diglycidyl ether bisphenol A (DGEBA). Thermomechanical properties of diglycidyl ether n-alkyl bisferulate resins cured with isophorone diamine were governed by the length of alpha,omega-diols that link glycidyl ether ferulate units. That is, the glassy phase modulus and alpha transition temperatures range from 3400-2400 MPa (at 25 degrees C) and 40-53 degrees C (peak of E''), respectively. Furthermore, the onset of thermal degradation (T-d5%) varied from 331-300 degrees C. Chemical recycling of cured epoxy resins was performed by static immersion in 10 w/w sodium hydroxide aqueous solutions at 60 degrees C. Times required for complete conversion of cured resins to water-soluble degradation products was also alpha,omega-diol length dependent and varied from 5 to 65 h. Thus, diglycidyl ether of n-alkyl bisferulate resins provides a viable biobased alternative to BPA epoxy resins as well as the option of chemical degradability and recovery of fillers in composite applications.