The United Nations Educational, Scientific and Cultural Organization (UNESCO) proclaimed in 2005 that Ugandan bark cloth is largely produced from
Worldwide, researchers are embroiled in a race for niche products whereby industries can boost production processes as well as putting into consideration the laws of sustainability. The quest for structural materials, which are environmentally friendly, to mitigate global warming effects is on the agenda of industrialized nations and recommendations are put forward for production of recyclable, biodegradable products or materials with zero emissions.
Transition to a more sustainable biobased economy, as a political consequence of the Kyoto protocol on global climate change, includes a shift from petrochemical to renewable sources.
The ecological “green” image of cellulosic fibers is the leading argument for innovation and development of products which are biodegradable and can be applied to automotive industries [
Plant-based fibers like flax, hemp, nettle, and kenaf which have been used to provide fiber in the Western world have attracted renewed interest in textile and industrial composite applications [
The need for lightness of materials with superb performance characteristics has sparked interest in lightweight composite materials. The front seat drivers of low density coupled with excellent mechanical properties of natural fibrous composites have a double impact in this respect. Carbon, glass, and Kevlar are the leading providers of fiber for composite reinforcement. The bottleneck is that their feedstock is from petroleum sources and has disposal concerns. With the dwindling petroleum resources coupled with high prices [
Numerous researches are flowing in on use of novel plants for production of fiber such as
According to the United Nations Educational, Scientific and Cultural Organization (UNESCO), bark cloth has been in production in Uganda for over six centuries; however, the nonwoven fleece which is produced through a series of pummeling processes has been confined to cultural regalia won at coronation of kings by Baganda a tribe in central Uganda and was also utilized during funerals and other witchcraft-related ceremonies. The technology transfer of bark cloth production from the elderly to the youth has been impeded by rural to urban migration of the youth and influence to modernization. That notwithstanding, in 2005, UNESCO proclaimed it as a “Masterpiece of the Oral and Intangible Heritage of Humanity” [
The front seat drivers and prospects of bark cloth are because it is a naturally occurring fabric meaning that it is biodegradable, cheap, low-specific weight, and so forth. The fact that it is a natural nonwoven material is advantageous whereby it can be applied as a starting material for heat insulation and composite products. The drawbacks are that it is hydrophilic in nature, tedious, and has lengthy extraction processes coupled with lack of mechanized equipment for extraction.
In this study, an exploratory investigation of nonwoven fabric from the inner bark of mutuba tree (
Despite the fact that bark cloth has been around dating back as far as 13th century, there has been limited data or scientific study on bark cloth. Therefore, in this study, for the first time we present the microstructure, static, thermal, and mechanical properties of bark cloth.
The extraction of the naturally occurring nonwoven as described by Rwawiire et al. (2011) [
(a) A man dressed in bark cloth harvesting bark from
For environmental sustainability, the debarked stem is wrapped with banana leaves, (Figure
Extraction of bark cloth from
The fabric thickness was obtained using UNI Thickness Meter. Measurement is done at different positions; the probe with a disc delivers a pressure of 1 kPa over an area of 25 cm2 for 30 s; then the thickness is obtained in mm. Ten readings were obtained and an average was statistically computed.
The bark cloth was subjected to alkali treatment of 5% NaOH solution. The bark cloth weighing 200.37 g was soaked in it for 6 hrs at room temperature thereafter thoroughly cleaned using distilled water to remove the alkali together with other impurities and then dried at room temperature.
The surface morphologies were investigated using a Vegas-Tescan scanning electron microscope with accelerating voltage of 20 KV.
Nicolet iN10 MX Scanning FTIR Microscope was used to provide the spectrum of the sample. The infrared absorbance spectrum of each sample was obtained in the range of 4000–700 cm−1.
Thermogravimetric analysis was carried out using a Mettler Toledo
The Perkin Elmer Differential Scanning Calorimeter DSC6 was used. Samples weighing approximately 10 mg using Waga Torsyjna-WT scale were placed in aluminum pans and sealed. The specimens were heated in an inert nitrogen atmosphere from room temperature (25°C) to 450°C at a heating rate of 10°C/min.
Nicolet iN10 MX Scanning FTIR Microscope was used to provide the spectrum of the sample. The FT-IR spectrum of each sample was obtained in the range of 4000–700 cm−1 in the transmission mode.
The fabric strength was quantified through measurements of samples for the bursting strength of the nonwoven fleece. Samples measuring 5 cm by 15 cm were tested using a Labotech fabric tensile testing machine at room temperature.
SEM was used to study the fabric morphology and images of the microstructure of the fabrics were obtained. The front seat drivers of SEM against optical microscope are that SEM has a high depth of field even at high magnifications. Ghassemieh et al. (2002) [
Figure
SEM morphology of transverse sections of bark cloth at magnifications 200x, 500x, and 1000x.
The top surface of bark cloth (Figure
SEM morphology of top surface of untreated bark cloth at magnifications (a) 50x, (b) 100x, and (c) 500x.
There is slight change in the color appearance of the fabric after alkaline treatment (Figure
SEM morphology of treated bark cloth at magnifications (a) 50x, (b) and (c) 100x, and (d) 500x.
The mean fabric thickness was computed as 1.084 mm from five samples of readings at different positions of the fabric.
The mean strength of the fabric in the fiber direction was 101.7 N and 23.5 N transverse. Since bark cloth fibers are aligned at angles (Figure
Approximate fiber arrangement of bark cloth.
Functional groups assignments and their respective bonding interactions of bark cloth can be deduced using Fourier transform infrared s pectroscopy (Figure
Fourier transform infrared spectra of bark cloth.
A broad absorption band at 3363 cm−1 is due to O–H stretching vibrations of cellulose and hemicelluloses. The band at 2929 cm−1 corresponds to CH2 and CH3 stretching vibrations [
After this peak, the sudden leveling off shows that the hemicelluloses are removed from the fiber. Aromatic vibration of benzene ring in lignin may be at 1615 cm−1. The absorption band at 1529 cm−1 was owing to CH2 bending in lignin, whereas the peak at 1445 cm−1 was due to O–H in-plane bending [
Nascimento et al. (2012) [
Thermogram of bark cloth.
The second stage accounting to about 70% weight loss starts from about 220°C to 370°C with a maximum decomposition temperature corresponding to around 325°C. The temperature range 200°C–315°C corresponds to the cleavage of glycosidic linkages of cellulose which leads to formation of H2O, CO2, alkanes, and other hydrocarbon derivatives [
Bark cloth thermograms have showed that the fabric is stable below 200°C; therefore, alternatives of composite fiber reinforcement can be explored provided that the working and production temperature of composites is kept under this temperature.
The first peak at 85.35°C (Figure
Differential scanning calorimetry of untreated and alkaline-treated bark cloth.
Bark cloth extracted from
Bark cloth is a porous fabric made of cellulosic material; the microfibers were found to be aligned in a fairly orderly manner at angles close to 45°. Thermal properties of the fabric show that it is stable below temperatures of 200°C; therefore, the fabric can be explored for composite reinforcement. It was observed that alkaline treatments positively influence the thermal properties of the fabric, raising the onset temperature of cellulose decomposition, meaning that if used for composite reinforcement, chemical surface treatments will improve the performance properties of bark cloth as reinforcement for composites.
The first author is grateful to God for life Busitema University for granting a study leave, and also to the Technical University of Liberec for funding the research.