الفهرس 
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Abstract
The morphology and tensile properties of electrospun CA and PVC were evaluated against solution concentration. CA was dissolved in 2:1 w/w acetone-DMAc and in 3:2 w/w acetone-DMF solvent systems while PVC was dissolved in 1:1 w/w THF-DMF. Beads and beaded fibers were obtained at low solution concentration. The number of beads reduced and fiber diameter increased as solution concentration was increased leading to production of smoother and more uniform fibers. Smooth fibers were achieved starting at 14 wt. % CA from acetone-DMAc solvent system at an average diameter of 113 nm. Acetone-DMF solvent system gave fairly smooth fibers at 16 wt. % CA with an average diameter of just 104 nm. Smooth PVC nanofibers were obtained starting at 14 wt. % PVC at an average diameter of 253 nm. The variation in morphology of the nanofibers was attributed to the change of solution properties as concentration was changed and the different effects of the electrospinning process on these properties. For the mechanical properties, increase in solution concentration resulted in a direct increase in specific peak stress, young’s modulus and work of rupture. The results showed that the percentage increase in tensile strength, young’s modulus and work of rupture were 96.7, 216.7 and 162.8% respectively for CA in acetone-DMAc solvent system, and 253.6, 350 and 1564.3% respectively for PVC with increase in solution concentration from 12 to 16%. The improved mechanical properties of both CA and PVC nanofibrous mats implied a major influence by solution concentration which was attributed to the effects of solution concentration on fiber morphology and the disappearance of beads. CA and PVC cast films had their mechanical properties compared to those of the electrospun nanofibrous mats at 16 wt. % solution concentration. It was found that cast films have higher tensile strength than randomly oriented nanofibrous mats due to their different methods of fabrication leading to different structures with different properties. The tensile properties of PVC nanocomposite sheets prepared from a sandwich of a nanofibrous mat between two cast films were evaluated and it was observed that unlike nanofibrous mats and cast films, the nanocomposite sheets exhibited multi stage rupture as the components failed at different instances. Increasing the volume fraction of the nanofibers in the nanocomposite resulted in a decrease in the tensile strength of the nanocomposite. This was seen when the volume fraction of the nanofibers was increased 69from 0.11 to 0.54 resulting in reduction of specific peak stress of the composite from 0.022 to 0.013 N/tex. This was attributed to the increase in mass of the nanocomposite without any increase in its effective strength since the nanofibrous mat was the weaker of the composing materials. Air permeability tests on the nanofibrous mats showed that CA mats are less porous than PVC mats due to their smaller fiber diameter. Thinner fibers have more fiber crossings within the membrane, hence have smaller pore sizes which influences flow. Nanofibers with smaller diameters also have a higher specific surface hence will result in higher resistance to air flow. Addition of AgNPs into PVC and CA electrospinning solutions leads to a decrease in the diameters of the nanofibers. An increase in AgNPs content in the electrospinning solutions from 0 to 1 wt.% silver resulted in the decrease in diameter from 104nm to 87nm for 16 wt. % CA in acetone-DMF solvent system and from 275nm to 244nm for PVC. Evaluation of the antifungal properties of CA and PVC electrospun nanofibrous mats and cast films showed that nanofibrous mats loaded with AgNPs exhibit significant reduction in the formation and growth of fungi compared to neat cast films and neat nanofibrous mats. More antifungal tests, however, need to be done for CA samples since the cast films had lower formation of fungi than on the nanofibrous mats contrary expectation and previous studies. from this study, the use of antifungal loaded nanofibrous mats as package materials for fresh fruits and vegetables is found to be quite promising. A combination of electrospinning and solvent casting technology could result in highly functional antifungal packaging materials, particularly making use of environmentally friendly polymers such as CA. More experiments could be done with inclusion of relevant packaging materials already in the market e.g. PVC cling films.