Effects of polymer rheology on the production of nanofibers from biopoylmers by using electrospinning method

Electrospinning is known to be the most convenient, easy and efficient nanofiber production method. Determining the important parameters necessary for the prediction of a successful electrospinning process from solution properties is essential, yet, not easy in the case of biopolymers due to their distinct natures. As the first objective, the effect of rheological parameters, namely zero shear viscosity, tip viscosity, elastic modulus, phase angle, cohesive energy, on the formation of smooth pectin nanofibers was evaluated simultaneously. Low methyl esterified amidated pectin solutions at different concentrations were blended with polyethylene oxide (PEO) at different molecular weights. Non-beaded nanofibers were obtained only when PEO2000 was used in the blends. Our results showed that (1) the viscosity of the solution is not an indication of jet formation, but once the jet is formed, high zero shear viscosity and high tip viscosity are required to maintain a dominant whipping instability for smooth nanofiber formation and (2) while evaluating the elasticity of the spinning solutions, comparing only the elastic modulus values would be misleading, since low phase angle values are also necessary for pectin solutions to be electrospun into nonbeaded fibers. As the second objective, obtained pectin nanofibers were used to develop a food packaging material. Plasticizer added fibers were subjected to annealing, to obtain homogenous and transparent fılms with reduced porosity. The annealing conditions (temperature, time and applied load) were optimized for each electrospun mat. Addition of plasticizer was found to be crucial to accomplish homogenous fılms. The results showed that the 30 wt. percent glycerol-containing fibers coalesced more easily at 140 oC and under 12 kN for 1 minute to form films with lower porosity and higher transparency. The optimal pectin-based film was, finally, applied as an inner-layer in a multilayer structure based on two external electrospun layers of poly(3hydroxybutyrate-co-3-hydroxyvalerate). The barrier properties of the multilayers showed that the resultant biopolymer multilayer films can be considered as promising materials to be utilized for food packaging applications.