A STUDY OF MORPHOLOGY AND MECHANICAL PROPERTIES OF ELECTROSPUN PVA-LEVAN FIBER

• Main Author: Furqan Abdillah, Bagus
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/68078
• Institution: Institut Teknologi Bandung

Nanofibers have a wide range of applications including air filtration, drug delivery and liquid filtration. The most popular method in the manufacture of nanofibers is electrospinning because of its convenience and high degree of control over the fibers being formed. Various natural and synthetic polymers have been prepared using electropsinning method and have attracted great attention due to their controllability and potential applications in various fields such as tissue engineering, drug delivery, wound dressings, batteries, and protective clothing. Some examples of natural polymers used to make electrospin fibers include collagen, gelatin, chitosan, cellulose acetate, hyaluronic acid and levan. Levan is a natural polymer that has a wide range of potential applications, although studies on the manufacture of levan fibers are still lack. Therefore, in this study, the effect of levan addition on the mechanical and morphological properties of PVA and levan mixed fibers was studied. PVA was chosen because it has the same functional group as levan and is often used as a fiber-forming template for biopolymers that are difficult to form fibers such as levan. Morphological and mechanical properties are focused on this research because these two properties are always studied in the manufacture of fibers regardless of the purpose of the application. The levan used in this study was produced using levansucrase lsbl-bk1. This enzyme is a recombinant enzyme expressed by Eschericia coli BL21 (DE3)pLysS containing the plasmid pET-lsbl-bk1. The produced levan was purified by dialysis technique for 3 days until the nucleic acid and protein were not detected under nanodrop. The obtained levan was also verified by comparing the FTIR spectra of the produced levan with the standard levan. The standard levan absorption at wavenumbers of 3440 cm-1, 2931 cm-1 and 1643 cm-1 which respectively show O-H, C-H and C=O bonds can also be found in the produced levan. The absorption in the fingerprint region also shows a similar spectral profile between the standard levan and the produced levan. The manufacture of PVA-levan fiber is carried out by electrospinning method using conditions 15% PVA concentration, 24 kV voltage, 1 mL/hour flow rate, 15 cm path distance and 8 Hz rotating speed of the collecting drum. In this study it was found that humidity greatly affects the formation of fibers. Fibers can form fine at 69-55% humidity. The synthesized fibers are crosslinked to increase their stability in the aqueous environment. The physical crosslinking method by heating at 150°C for 5 hours was chosen because it was reported to have better stability than chemical crosslinking. The crosslinked fibers were seen for their morphology using SEM and it was found that the fibers had a smooth morphology and were free from beaded structures. The diameter of the crosslinked PVA fiber was 319.72±3.06 nm and the fiber with levan concentration of 1, 3 and 5% respectively had a diameter of 194.05±10.26 nm, 329.75±7.60 nm, and 342.97±6.86 nm. The higher the levan concentration, the larger the fiber diameter. The higher the levan concentration also resulted in the decreased mechanical properties of the fiber when tested in tensile test. The obtained fiber has a modulus of elasticity of 25.02±3.05 MPa, yield strength of 0.85±0.46 MPa and tensile strength of 4.01±0.86 MPa for PVA. Fiber with the addition of 1% levan has a modulus of elasticity of 16.44±0.77 MPa, yield strength of 2.00±0.38 MPa and tensile strength of 4.86±0.45 MPa. Fiber with the addition of 3% levan has a modulus of elasticity of 12.68±1.36 MPa, yield strength of 1.54±0.04 MPa and tensile strength of 3.63±0.15 MPa. Finally, fiber with 5% levan added has a modulus of elasticity of 11.9±1.28 MPa, yield strength of 0.43±0.16 MPa and tensile strength of 2.05±0.38 MPa.