Advances in Phytochemistry, Textile and Renewable Energy Research for
Industrial Growth – Nzila et al. (Eds)
© 2022 Copyright the Author(s), ISBN: 978-1-032-11871-0
Open Access: www.taylorfrancis.com, CC BY-NC-ND 4.0 license
Effects of alkaline and microwave surface modification on Calotropis
procera bast fibres for development of fibre-reinforced polylactic acid
composite
E.K. Langat & D.G. Njuguna
Department of Manufacturing, Industrial and Textile Engineering, School of Engineering, Moi University, Eldoret,
Kenya
Africa Centre of Excellence II in Phytochemicals, Textiles and Renewable Energy (ACE II PTRE), Moi University,
Eldoret, Kenya
ABSTRACT: Natural fibres have been used as reinforcement in a polymer matrix. One of the major challenges
is incompatibility with matrices. In this study, Calotropis procera plant bast fibres were extracted from stems
using the decortication method. First, the samples were treated in varied alkaline solution concentrations of
sodium hydroxide for different durations of treatment time. Second, the samples were subjected to microwave
treatment at various power levels for different duration of treatment time. Fibres with optimum tensile properties
were used with polylactic acid (PLA) matrix to fabricate biocomposite materials. Both alkaline-treated and
microwave-treated samples showed a significant increase in tensile properties and decrease in fibre linear density
when compared with untreated samples. Alkaline treatment 5 w/v% solution for 1 hour and microwave irradiation
with 231Watts for 4 minutes treatment period were optimum for fibres modification. Tensile strength and tensile
modulus of PLA/alkaline-treated-CPBF and PLA/microwave-treated-CPBF improved by 34.27% and 20.46%
and by 21.22% and 15.54%, respectively.
1 BACKGROUND
1.1 Materials used for composites
In recent years, there has been a great awareness
towards preserving our natural resources and the
environment. With increased economic development
and energy consumption, alternative methods and
materials have been developed to replace petroleumbased products by bio-based materials. Moreover, the
emphasis has been to reduce the use of petroleumbased products which are a key contributor of greenhouse gas emissions due to the production of high
levels of carbon dioxide during extraction and processing. The other emphasized issue is the utilization
of new renewable resources (Huda & Yang, 2008;
Mohanty, Misra, & Drzal, 2002). Most of the polymer
materials are made up of non-renewable and nondegradable synthetic plastics and their waste occupies
the top position in landfills (Ariadurai, 2013). Plastics cause severe environmental and health damage
(Bashir, 2013). Therefore there is a need to reduce
plastic use and disposal in Africa and increase the
use of more eco-friendly materials (Fuqua, Huo, &
Ulven, 2012; Puglia, Biagiotti, & Kenny, 2005; Rayne,
2008) through further developing alternative methods
and exploring new natural materials to replace
or reduce petroleum-based products by bio-based
materials.
1.2 Biocomposites
Biocomposites are renewable, recyclable, biodegradable and environmentfriendly resources which can be
used for daily life applications in the construction,
automobile, and biomedical sectors (Li, Panigrahi, &
Tabil, 2009). Natural fibre-reinforced biocomposites
using biodegradable polymers have been claimed as
the most environmentfriendly bioproducts (dos Santos Rosa & Lenz, 2013). Studies have been conducted
on the manufacture of biocomposites with the use
of biodegradable polymers. Polymers such as polylactic acid (PLA) and polycaprolactone (PCL) are
used to manufacture biocomposites depending on
their desired properties and the end-use of the product (Gunatillake & Adhikari, 2003). The realization
of a biodegradable composite is essentially possible
by combining a biodegradable matrix with natural
fibre reinforcement. Natural fibre-based PLA composites present the opportunity of achieving several
desired properties. The factors considered in characterization are fibre volume/weight fraction, stacking
sequence of the fibre layers, methods of processing,
DOI 10.1201/9781003221968-14
111
Industrial Growth – Nzila et al. (Eds)
© 2022 Copyright the Author(s), ISBN: 978-1-032-11871-0
Open Access: www.taylorfrancis.com, CC BY-NC-ND 4.0 license
Effects of alkaline and microwave surface modification on Calotropis
procera bast fibres for development of fibre-reinforced polylactic acid
composite
E.K. Langat & D.G. Njuguna
Department of Manufacturing, Industrial and Textile Engineering, School of Engineering, Moi University, Eldoret,
Kenya
Africa Centre of Excellence II in Phytochemicals, Textiles and Renewable Energy (ACE II PTRE), Moi University,
Eldoret, Kenya
ABSTRACT: Natural fibres have been used as reinforcement in a polymer matrix. One of the major challenges
is incompatibility with matrices. In this study, Calotropis procera plant bast fibres were extracted from stems
using the decortication method. First, the samples were treated in varied alkaline solution concentrations of
sodium hydroxide for different durations of treatment time. Second, the samples were subjected to microwave
treatment at various power levels for different duration of treatment time. Fibres with optimum tensile properties
were used with polylactic acid (PLA) matrix to fabricate biocomposite materials. Both alkaline-treated and
microwave-treated samples showed a significant increase in tensile properties and decrease in fibre linear density
when compared with untreated samples. Alkaline treatment 5 w/v% solution for 1 hour and microwave irradiation
with 231Watts for 4 minutes treatment period were optimum for fibres modification. Tensile strength and tensile
modulus of PLA/alkaline-treated-CPBF and PLA/microwave-treated-CPBF improved by 34.27% and 20.46%
and by 21.22% and 15.54%, respectively.
1 BACKGROUND
1.1 Materials used for composites
In recent years, there has been a great awareness
towards preserving our natural resources and the
environment. With increased economic development
and energy consumption, alternative methods and
materials have been developed to replace petroleumbased products by bio-based materials. Moreover, the
emphasis has been to reduce the use of petroleumbased products which are a key contributor of greenhouse gas emissions due to the production of high
levels of carbon dioxide during extraction and processing. The other emphasized issue is the utilization
of new renewable resources (Huda & Yang, 2008;
Mohanty, Misra, & Drzal, 2002). Most of the polymer
materials are made up of non-renewable and nondegradable synthetic plastics and their waste occupies
the top position in landfills (Ariadurai, 2013). Plastics cause severe environmental and health damage
(Bashir, 2013). Therefore there is a need to reduce
plastic use and disposal in Africa and increase the
use of more eco-friendly materials (Fuqua, Huo, &
Ulven, 2012; Puglia, Biagiotti, & Kenny, 2005; Rayne,
2008) through further developing alternative methods
and exploring new natural materials to replace
or reduce petroleum-based products by bio-based
materials.
1.2 Biocomposites
Biocomposites are renewable, recyclable, biodegradable and environmentfriendly resources which can be
used for daily life applications in the construction,
automobile, and biomedical sectors (Li, Panigrahi, &
Tabil, 2009). Natural fibre-reinforced biocomposites
using biodegradable polymers have been claimed as
the most environmentfriendly bioproducts (dos Santos Rosa & Lenz, 2013). Studies have been conducted
on the manufacture of biocomposites with the use
of biodegradable polymers. Polymers such as polylactic acid (PLA) and polycaprolactone (PCL) are
used to manufacture biocomposites depending on
their desired properties and the end-use of the product (Gunatillake & Adhikari, 2003). The realization
of a biodegradable composite is essentially possible
by combining a biodegradable matrix with natural
fibre reinforcement. Natural fibre-based PLA composites present the opportunity of achieving several
desired properties. The factors considered in characterization are fibre volume/weight fraction, stacking
sequence of the fibre layers, methods of processing,
DOI 10.1201/9781003221968-14
111