Multilayer bacterial cellulose/resole nanocomposites: Relationship between structural and electro-thermo-mechanical properties

The aim of this research was to fabricate multilayer insulator nanocomposites using phenolic resin impregnated bacterial cellulose (BC) handsheets and investigate the relationships between their structural and electro-thermo-mechanical properties. G. xylinus was incubated in a static Hestrin-Schramm culture at 28 °C for 14 days. Then, BC aqueous suspension was added to kraft pulp aqueous suspension. The content of BC that was added to the pulp suspension was as follows: 5, 10 and 15%. The disintegrated BC was turned into handsheets by a vacuum method. Dried handsheets were immersed in phenolic resin. To obtain composites, 5 immersed handsheets from each treatment were laid-up and hot pressed at 150 °C under 100 MPa pressure for 10 min. The specimens were characterized by means of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal mechanical analysis (TMA), field-emission scanning electron microscopy (FE-SEM) techniques and insulating tests as dielectric loss factor and breakdown voltage. The results of thermal analysis showed an improvement in the thermal stability and an increase in the evaporation enthalpy of prepared samples with higher BC content. The mechanical examinations indicated that by increasing BC content in nanocomposites, the loss modulus and tan delta increased and the storage modulus of specimens decreased. The coefficient of thermal expansion (CTE) of samples diminished with increase of BC content. FE-SEM characterization showed different qualities of resin impregnation of the papers. The results of insulating tests confirmed that dielectric loss tangent and dielectric breakdown voltage increased in the specimens with higher BC content.