Macromol. Mater. Eng. 276/277, 1–24 (2000) 1
Biofibres, biodegradable polymers and biocomposites:
An overview
A. K. Mohantya, b, M. Misraa, b, G. Hinrichsen*
Technical University of Berlin, Institute of Nonmetallic Materials, Polymer Physics, Englische Str. 20, D-10587 Berlin,
Germany
(Received: September 27, 1999; revised: March 2, 2000)
Summary of contents
1. Introduction
2. Reinforcing biofibres
2.1 Chemical constituents and structural aspects
2.2 Properties of biofibres
2.3 Degradation properties of biofibres
2.4 Cost aspects, availability and sustainable develop-
ment of biofibres
3. Biodegradable polymers
3.1 Definition
3.2 Classification
Review: Recently the critical discussion about the preser-
vation of natural resources and recycling has led to the
renewed interest concerning biomaterials with the focus
on renewable raw materials. Because of increasing envir-
onmental consciousness and demands of legislative autho-
rities, use and removal of traditional composite structures,
usually made of glass, carbon or aramid fibers being rein-
forced with epoxy, unsaturated polyester, or phenolics, are
considered critically. Recent advances in natural fiber
development, genetic engineering and composite science
offer significant opportunities for improved materials
from renewable resources with enhanced support for glo-
bal sustainability. The important feature of composite
materials is that they can be designed and tailored to meet
different requirements. Since natural fibers are cheap and
biodegradable, the biodegradable composites from biofi-
bers and biodegradable polymers will render a contribu-
tion in the 21st century due to serious environmental pro-
blem. Biodegradable polymers have offered scientists a
possible solution to waste-disposal problems associated
with traditional petroleum-derived plastics. For scientists
the real challenge lies in finding applications which would
consume sufficiently large quantities of these materials to
lead price reduction, allowing biodegradable polymers to
compete economically in the market. Today’s much better
performance of traditional plastics are the outcome of
continued R&D efforts of last several years; however the
existing biodegradable polymers came to public only few
years back. Prices of biodegradable polymers can be
reduced on mass scale production; and such mass scale
production will be feasible through constant R&D efforts
of scientists to improve the performance of biodegradable
plastics. Manufacture of biodegradable composites from
such biodegradable plastics will enhance the demand of
such materials. The structural aspects and properties of
several biofibers and biodegradable polymers, recent
developments of different biodegradable polymers and
biocomposites are discussed in this review article. Colla-
borative R&D efforts among material scientists and engi-
neers as well as intensive co-operation and co-ordination
among industries, research institutions and government
are essential to find various commercial applications of
biocomposites even beyond to our imagination.
Macromol. Mater. Eng. 276/277 i WILEY-VCH Verlag GmbH, D-69451 Weinheim 2000 1438-7492/2000/0103–0001$17.50+.50/0
a Present address: Composite Materials and Structures Center,
Michigan State University, 2100 Engineering Building, East
Lansing, MI 48824-1226, USA.
b Home address: Polymer & Composites Laboratory, Depart-
ment of Chemistry, Ravenshaw College (Autonomous), Cut-
tack – 753003, Orissa, India.
Life cycle of compostable, biodegradable polymers (after
ref.78))

2 A. K. Mohanty, M. Misra, G. Hinrichsen
3.3 Importance of biodegradable polymers from
renewable resources
3.4 Structure, synthesis and properties of biodegrad-
able polymers
3.4.1 Aliphatic polyesters
3.4.2 Polyester amides
3.4.3 Starch plastics
3.4.4 Cellulose acetate
3.4.5 Soy plastic
3.5 Biodegradable plastics vs. traditional plastics
4. Biocomposites
4.1 Cellulose fibre based biocomposites
4.2 Flax, hemp, and ramie based biocomposites
4.3 Jute based biocomposites
4.4 Miscellaneous biocomposites
4.5 Application of biocomposites
5. Conclusion
Acknowledgement
1. Introduction
Fibre-reinforced plastic composites began with cellulose
fibre in phenolics in 1908, later extending to urea and
melamine, and reaching commodity status in the 1940s
with glass fibre in unsaturated polyesters. From guitars,
tennis racquets and cars to microlight aircrafts, electronic
components and artificial joints, composites are finding
use in diverse fields. Because of increasing environmen-
tal consciousness and demands of legislative authorities,
the manufacture, use and removal of traditional compo-
site structures, usually made of glass, carbon or aramid
fibres being reinforced with epoxy, unsaturated polyester
resins, polyurethanes, or phenolics, are considered criti-
cally. The most important disadvantage of such compo-
site materials is the problem of convenient removal after
the end of life time, as the components are closely inter-
connected, relatively stable and therefore difficult to
separate and recycle1). In the modern polymer technology
it is a great demand that every material should especially
be adapted to the environment. In order to successfully
meet the environmental and recycling problems, the DLR
(Deutsches Zentrum fu¨r Luft- und Raumfart e.V.) Insti-
tute of Structural Mechanics, applying their knowledge in
composite technology in a new broadened way2), devel-
oped an innovative idea in 1989.
By embedding natural reinforcing fibres, e.g. flax,
hemp, ramie, etc. into biopolymeric matrix made of deri-
vatives from cellulose, starch, lactic acid, etc; new fibre
reinforced materials called biocomposites were created
and are still being developed2–8). Biocomposites consist of
biodegradable polymer as matrix material and usually
biofibre as reinforcing element. Since both components
are biodegradable, the composite as the integral part is
also expected to be biodegradable. Biofibres, i. e., natural
polymers, are generally biodegradable but they do not
possess the necessary thermal and mechanical properties
desirable for engineering plastics. On the other hand, the
best engineering plastics are obtained from synthetic
polymers, but they are non-biodegradable. A lot of R&D
work has been carried out on biofibre reinforced synthetic
polymers. The composites of natural fibres and non-bio-
degradable synthetic polymers may offer a new class of
materials but are not completely biodegradable. Govern-
ment regulations and growing environmental awareness
throughout the world have triggered a paradigm shift
towards designing materials compatible with the environ-
ment9). The biofibres derived from annually renewable
resources, as reinforcing fibres in both thermoplastic and
thermoset matrix composites provide positive environ-
mental benefits with respect to ultimate disposability and
raw material utilization10). Auto makers now see strong
promise in natural fiber reinforcements11). We find a num-
ber of publications on natural fiber composites in auto-
motive applications12–14). Literature also shows some
reviews on cellulosic as well as ligno-cellulosic fiber
based composites15–18). Advantages of biofibres over tra-
ditional reinforcing materials such as glass fibres, talc
and mica are9): low cost, low density, high toughness,
acceptable specific strength properties, reduced tool wear,
reduced dermal and respiratory irritation, good thermal
properties, ease of separation, enhanced energy recovery
and biodegradability. The main drawback of biofibres is
their hydrophilic nature which lowers the compatibility
with hydrophobic polymeric matrix during composite
fabrications. The other disadvantage is the relatively low
processing temperature required due to the possibility of
fibre degradation and/or the possibility of volatile emis-
sions that could affect composite properties. The proces-
sing temperatures for most of the biofibres are thus lim-
ited to about 2008C, although it is possible to use higher
temperatures for short periods19).
The annual disposal of over 10 million tons of plastics
in both the US and EC countries has raised the demand
for means of managing this non-biodegradable waste
stream. The synthetic polymers have displaced metals,
glasses, ceramics and wood in many products, especially
in the area of packaging. The commodity plastics, the so
called “big four” polyethylene (PE), poly(propylene)
(PP), polystyrene (PS) and poly(vinyl chloride) (PVC) in
a variety of forms such as films, flexible bags and rigid
containers have revolutionized the packaging industry.
However, once these materials are discarded, they persist
in the environment without being degraded thus giving
rise to a multitude of ecological and environmental con-
cerns. The important feature of composite materials is
that they can be designed and tailored to meet different
requirements. Since biofibres are cheap and biodegrad-
able, the biocomposites from biofibre reinforcced biode-
gradable polymers will render a contribution in 21st cen-
tury due to serious environmental problem. Now it is a