Fabrication of Electrospun Nanofibers for Technical Textiles

Abstract

This thesis is focused on the preparation of novel electrospun fibers mat (EFM) by embedding UV-light sensitive compound [1’-3’-Dihydro-1’,3’,3’-trimethyl-6-nitrospiro [2H-1-benzopyran-2,2’-(2H)-Indole] (Indole) in poly(Ɛ-caprolactone) (PCL) polymer matrix via electrospinning. The resulting PCL/Indole EFMs can be used for functional applications including pattern image recording on EFMs and its potential to be used for making smart photochromic nonwoven fabric. Moreover, novel electrospun fiber blends (PCL/Cellulose and Zein/Cellulose Acetate) were fabricated at various ratios to achieve hydrophilic characteristics. They can potentially be used as a substrate for biosensor strip and in other biomaterials which requires high wicking rate. Also, colored EFM (Polyurethane EFM dyed with disperse dyes) was prepared for potential application in casual and fashion apparels.

In the first part, a nonionic photochromic spiropyran dye (Indole) was successfully embedded as a guest into a host PCL polymer matrix via electrospinning for the first time. The resulting PCL/Indole EFM have good photo-switching properties upon alternating ultraviolet and visible light irradiations. It was found that patterned color image can be recorded on the photochromic PCL/Indole EFM using photo-masked UV irradiation. The subsequent visible light irradiation of the mat completely erased the recorded patterned color image. The PCL/Indole EFM can potentially be used in making smart photochromic nonwoven fabric. Furthermore, the rate of photocoloration was observed faster (ΔE=50 in 8 min) than the rate of decoloration for PCL/Indole EFM. The analysis of washing fastness of PCL/Indole EFM revealed good to excellent ratings; which is an essential requirement for colored apparels.

In the second part, a series of novel PCL/Cellulose Acetate (CA) EFMs were prepared via electrospinning. The PCL/CA EFMs were found to be hydrophobic. Partial miscibility in between PCL and CA were revealed probably due to the hydrogen bonding in between the carbonyl groups of PCL and hydroxyl groups of CA. PCL/CA EFMs were further treated in an aqueous alkaline solution to convert CA into Cellulose (CEL). The novel PCL/CEL EFMs showed improved wetting properties in comparison to the PCL/CA EFMs. In PCL/CEL EFMs, PCL component provides dimensional stability and the CEL component offers the hydrophilicity. Moreover, the PCL/CEL, (1:4) blend exhibited the most uniform and fast wicking rate demonstrating that they can be used in applications where high wicking rates are required including liquid biofilter and biosensor strip.

In the third part, polymer solutions of Zein and CA were mixed together at different ratios for electrospinning with an aim to achieve good wetting properties in the resulting EFMs. Zein polymer was selected on account of its poor morphological stability in water. Zein/CA EFMs do not require any chemical treatment such as deacetylation to increase hydrophilicity. The use of Zein is interim in Zein/CA EFMs as it loses its fibrous structure when immersed in water forming a film, which results in an increase in the porosity of the mat. As a result, water diffuses quickly within the mat making it hydrophilic. In Zein/CA EFMs, CA polymer provides the dimensional stability. Significantly, improved thermal properties including higher glass transition temperature (Tg) and higher degradation temperature (TD) were revealed for Zein/CA EFMs in comparison to the pure Zein EFM. The Zein/CA EFMs can be used as a substrate for biosensor strip and as a scaffold in tissue engineering.

In the fourth part, dyeing of polyurethane (PU) nanofibers were carried out with commercially available disperse dyes by pad-dry-cure method. It was revealed that the high energy level disperse dye (CI Disperse Red 167:1) produced better color strength (K/S) than the low energy level disperse dye (CI Disperse Blue 56). The results revealed very good K/S with acceptable color fastness properties. Furthermore, dyed PU EFM displayed smooth morphology revealing good resistance to wet and heat treatments carried out during disperse dyeing. The colored and breathable PU EFM can potentially be used for casual and fashion apparels.