CHAPTER 5
PREPARATION, MECHANICAL
AND ELECTRICAL STUDY OF
JUTE/GLASS REINFORCED
COMPOSITES AND THEIR
PHYSICO-CHEMICAL STUDY
Preparation…
155
CHAPTER 5
Preparation, mechanical and electrical study of jute/glass reinforced
composites and their physico-chemical study
5.1 General introduction
Composites can be defined as materials that consist of two or more
chemically and physically different phases separated by a distinct interface.
The different systems are combined judiciously to achieve a system with more
useful structural or functional properties non attainable by any of the
constituent alone. Composites, the wonder materials are becoming an
essential part of today’s materials due to the advantages such as low weight,
corrosion resistance, high fatigue strength, and faster assembly. They are
extensively used as materials in making aircraft structures, electronic
packaging to medical equipment, and space vehicle to home building [1]. The
basic difference between blends and composites is that the two main
constituents in the composites remain recognizable while these may not be
recognizable in blends. The predominant useful materials used in our day-to-
day life are wood, concrete, ceramics, and so on. Surprisingly, the most
important polymeric composites are found in nature and these are known as
natural composites.
Composites are combinations of materials differing in composition,
where the individual constituents retain their separate identities. These
separate constituents act together to give the necessary mechanical strength
or stiffness to the composite part. Composite material is a material composed
of two or more distinct phases (matrix phase and dispersed phase) and
having bulk properties significantly different from those of any of the
constituents. Matrix phase is the primary phase having a continuous
character. Matrix is usually more ductile and less hard phase. It holds the
dispersed phase and shares a load with it. Dispersed (reinforcing) phase is
1. A. Shaw, S. Sriramula, P. D. Gosling, and M. K. Chryssanthopoulo, A
critical reliability evaluation of fibre reinforced composite materials based
on probabilistic micro and macro-mechanical analysis, Composites Part
B, 41, 446–453, 2010.
Preparation…
156
embedded in the matrix in a discontinuous form. This secondary phase is
called the dispersed phase. Dispersed phase is usually stronger than the
matrix, therefore, it is sometimes called reinforcing phase.
Composite materials can be classified into three categories depending
on the type of matrix materials used such as metal matrix composites,
polymer matrix composites and ceramic matrix composites. Each type of
composite material is suitable for different applications. Among them, polymer
matrix composites are the composites consisting of polymer as matrix
material. These composites are characterized by the various properties such
as high stiffness, high tensile strength, high fracture toughness, good
corrosion and abrasion resistance, low cost, etc. There are two major classes
of polymers used as matrix materials such as thermoplastics and thermosets.
Thermoplastics (nylon, polypropylene, acrylics, etc.), can be repeatedly
softened and re-formed by application of heat. However, thermosets
(phenolic, epoxies, etc.) on the other hand, are materials that undergo a
curing process during part fabrication, after which they are rigid and cannot be
reformed. Among them epoxy is the most widely used matrix due to it
advantages like good adhesion to other materials, good mechanical
properties, good electrical insulating properties, good chemical and
environmental resistance, etc. Generally, the reinforcing material for polymer
matrix composites include synthetic fibers such as glass fiber, kevlar fiber,
carbon fiber, etc. or natural/cellulose fibers such as cotton, jute, kenaf,
bamboo fiber, etc.
Composites in structural applications have the following characteristics:
� They generally consist of two or more physically distinct and
mechanically separable materials.
� They are made by mixing the separate materials in such a way as to
achieve controlled and uniform dispersion of the constituents.
� They have superior mechanical properties and in some cases uniquely
different from the properties of their constituents [2].
2. C. Mayer, X. Wang, and M. Neitzel, Macro- and micro-impregnation
phenomena in continuous manufacturing of fabric reinforced
thermoplastic composites, Composites Part A, 29,783–793, 1998.
Preparation…
157
5.2 Natural fiber composites
Natural fibers may be classified by their origin as cellulosic (from
plants), protein (from animals) and mineral. Plant fibers may be further
classified a: seed hairs, such as cotton; bast (stem) fibers, such as linen from
the flax plant; hard (leaf) fibers, such as sisal; husk fibers, such as coconut.
However commercially important natural fibers can be obtained from the seed
hairs, stems, and leaves of plants (Fig. 5.1). The material properties of natural
fibers are comparable with those of synthetic ones, as tabulated in Table 5.1.
Cellulose is the main structural component that provides strength and stability
to the plant cell walls and is one of the most abundant organic compounds on
earth. The amount of cellulose in a fiber influences the properties, economics
of fiber production and the utility of the fiber for various applications [3].
Fig. 5.1: Classification of cellulosic fibers.
3. J. K. Pandey, S. H. Ahn, C. S. Lee, A. K. Mohanty and M. Misra, Recent
advances in the application of natural fiber based composites, Macromol.
Mater. Eng., 295, 975–989, 2010.
Preparation…
158
Table 5.1: Physical properties of some natural and synthetic fibers [4].
Fiber
Density
(g/cm3)
Elongation
(%)
Youngs
modulus
(GPa)
Tensile
strength
(MPa)
Specific
tensile
strength
Water
absorption
(%)
E-glass 2.5 2.5 70 2000–
3500
800–
1400
–
Aramide 1.4 3.3–3.7 63–67 3000–
3150
2140–
2250
–
Carbon 1.4 1.4–1.8 230–240 4000 2860 –
Flax 1.5 1.2–3.2 27–80 345-
1500
230–
1000
7
Cotton 1.5–1.6 3.0–10.0 5.5–12.6 287–800 190–530 8–25
Jute 1.3–1.5 1.5–1.8 10–55 393–800 300–610 12
Hemp 1.5 1.6 70 550–900 370–600 8
Sisal 1.3–1.5 2.0–2.5 9.4–28 511–635 390–490 11
Ramie 1.5 2.0–3.8 44–128 400–938 270–620 12–17
Coir 1.2 15–30 4–6 131–220 110–180 10
Glass, carbon, Kevlar, and boron fibers are being used as reinforcing
materials in fiber-reinforced plastics, which have been widely accepted as
materials for structural and nonstructural applications [5]. However, these
materials are resistant to biodegradation and can pose environmental
problems. Natural fibers from plants such as jute, bamboo, coir, sisal, and
pineapple are known to have very high strength and hence can be utilized for
many load-bearing applications. These fibers have special advantage in
comparison to synthetic fibers in that they are abundantly available, from a
renewable resource and are biodegradable. But all natural fibers are
hydrophilic in nature and have high moisture content, which leads to poor
4. E. Zini and M. Scandola, Green Composites: An Overview, Polym.
Compos., 32, 1905–1915, 2011.
5. D. Liu, A. D. McDaid and D. Q. Xie, Position control of an ionic polymer
metal composite actuated rotary joint using iterative feedback tuning,
Mechatronics, 21, 315–328, 2011.
Preparation…
159
interface between fiber and hydrophobic matrix. Several treatment methods
are employed to improve the interface in natural fiber composite [6].
Automobile industry in Europe has started using natural fiber composites in a
big way both for exterior and interior of car bodies because of stringent
environmental requirements.
Natural fibers are generally incompatible with the hydrophobic polymer
matrix and have a tendency to form aggregates. Therefore, the surface of
both (matrix and fibers) should be appropriately wetted to improve the
interfacial adhesion and to remove any impurities. The surface of hydrophobic
matrices should be modified by the introduction of polar groups by treating
them with oxidative chemicals such as chromic acid/acetic acid or chromic
acid/sulfuric acid [7]. Cold plasma chemistry opens up new avenues for the
surface modifications of materials for composites and other applications.
Various oxidative and nonoxidative chemical treatments are available for
natural and synthetic fibers to improve the bonding at the interface. Alkali
treatment has been proved to be an effective method for fiber modification
from as early as 1935. It has been reported that on treatment with alkali, some
of the wax components at the fiber surface are saponified and thereby
removed from the fiber surface. Increased fiber/matrix adhesion as a result of
improved surface area and increase in availability of the hydroxyl groups have
also been reported as a result of alkali treatment [8].
6. V. G. Geethamma, T. K. Mathew, R. Lakshminarayanan, and S.
Thomas, Composite of short coir fibres and natural rubber: effect of
chemical modification, loading and orientation of fibre, Polymer, 39,
1483–1491, 1998.
7. S. A. Paul, A. Boudenne, L. Ibos, Y. Candau, K. Joseph, and S. Thomas,
Effect of fiber loading and chemical treatments on thermophysical
properties of banana fiber/polypropylene commingled composite
materials, Composites Part A, 39, 1582–1588, 2008.
8. P. V. Joseph, Computer Sciences Technology, 62, 1357, 2002.
Preparation…
160
5.2.1 Applications of natural fiber composites
The natural fiber composites can be very cost effective material for
following applications:
� Building and construction industry: panels for partition and false ceiling,
partition boards, wall, floor, window and door frames, roof tiles, mobile
or pre-fabricated buildings which can be used in times of natural
calamities such as floods, cyclones, earthquakes, etc.
� Storage devices: post-boxes, grain storage silos, bio-gas containers,
etc.
� Furniture: chair, table, shower, bath units, etc.
� Electric devices: electrical appliances, pipes, etc.
� Everyday applications: lampshades, suitcases, helmets, etc.
� Transportation: automobile and railway coach interior, boat, etc.
The reason for the application of natural fibers in the automotive industry
includes:
� Low density: which may lead to a weight reduction of 10 to 30%
� Acceptable mechanical properties, good acoustic properties.
� Favorable processing properties, for instance low wear on tools, etc.
� Options for new production technologies and materials.
� Favorable accident performance, high stability, less splintering.
� Favorable ecobalance for part production.
� Favorable ecobalance during vehicle operation due to weight savings.
� Occupational health benefits compared to glass fibers during
production.
� No off-gassing of toxic compounds (in contrast to phenol resin bonded
wood and recycled cotton fiber parts).
� Price advantages both for the fibers and the applied technologies.
Preparation…
161
5.2.2 Advantages of natural fiber composites
The main advantages of natural fiber composites are:
� Low specific weight, resulting in a higher specific strength and stiffness
than glass fiber.
� It is a renewable source, the production requires little energy, and CO2
is used, while oxygen is given back to the environment.
� Producible with low investment at low cost, which makes the material
an interesting product for low wage countries.
� Reduced wear of tooling, healthier working condition, and no skin
irritation.
� Thermal recycling is possible, while glass causes problem in
combustion furnaces.
� Good thermal and acoustic insulating properties.
Jute is an attractive natural fiber for the reinforcement because of its
low cost, renewable nature and much lower energy requirement for
processing. Jute fiber contains high proportion of stiff natural cellulose. Rated
fibers of jute have three principle chemical constituents, namely α- cellulose,
hemicellulose and lignin. In addition, they contain minor constituents such as
fats and waxes, minerals, nitrogenous matter and trace of pigments like β-
carotene and xanthophylls. Several studies of fiber composition and
morphology have found that cellulose content and micro fibril angle tend to
control the mechanical properties of the cellulosic fibers. The specific
mechanical properties of the composites are comparable to those of the glass
fiber reinforced plastics (GRP). Various items such as school buildings, food
grain silos, wood substitutes, low cost housing units, roofing, pipes [9], etc.
have been fabricated from the jute fiber reinforced composites.
9. M. A. Semsarzadesh, Fiber matrix interactions in jute reinforced
polyester resin, Polym. Compos., 7, 23-25, 1986.
Preparation…
162
5.3 Glass fiber composites
Two commonly used glass fibers in the industry are E-glass and S-
glass. The primary material in most glass fibers is silica; to effectively produce
theses fibers, the ingredients must be melted in a furnace that at
temperatures of about 1,370 °C. Glass fibers are a popular choice for fiber
reinforcement due to advantageous properties such as high strength (tensile
strength of approximately 3.40 GPa), tolerance to high temperatures and
corrosive environments, and low cost. However, glass fibers have a relatively
low stiffness. Typically values of stiffness for glass fibers range from
approximately 70 to 90 GPa, whereas, the stiffness of carbon fiber can range
from 230 to 830 GPa.
Glass fiber-reinforced composite materials are attractive because their
properties can be tailored to meet the specific needs of a variety of
applications. The mechanical and thermal properties of a composite generally
follow the rule of mixtures. As glass fiber is the major component at 70–75%
by weight (50–60% by volume), selection of the correct glass product is
critical. Glass fiber reinforcement is available in many forms, including
continuous rovings, chopped fibers, fabrics, and nonwoven mats. In addition
to form, selection of a reinforcement product involves choosing a glass type,
chemistry on the glass (sizing) filament diameter, and tex. Glass formulation
or type governs mechanical, thermal, and corrosion properties, whereas
sizing protects the glass during handling and gives compatibility with the resin
system. Filament diameter and strand tex are chosen to balance physical
properties and manufacturing efficiency. A significant amount of tensile
strength, up to 50%, may be lost from a pristine single filament to a multi-
filament roving. To minimize this degradation, the utmost care and
consistency must be exercised in the fiber forming process. This, coupled with
selection of a high-performance glass formulation, enables use of composites
in highly demanding applications, such as pressure vessels and ballistic
armor [10].
10. J. M. Stickel and M. Nagarajan, Glass fiber-reinforced composites: from
formulation to application, Int. J. Appl. Glass Sci., 3, 122–136, 2012.
Preparation…
163
5.4 Fabrication of jute/glass fiber composites
For the preparation of jute/glass composites, 70 % of matrix material
was used (Table 5.2). Required quantity of resin was transferred into a 500 ml
beaker containing required methylethyl ketone and stirred well at room
temperature. To this solution 2 % methylethylketone peroxide and 1 % of 6%-
cobalt naphthenate were added as an initiator and an accelerator,
respectively. The solution was stirred well and was applied to jute/glass
fabrics (20cmX20cm) with a smooth brush and solvent was allowed to
evaporate at room temperature. Eight such jute and ten glass impregnated
fabrics were staked one over the other and kept between two teflon sheets.
These teflon sheets were kept between two preheated stainless steel plates
and pressed under 27.58 MPa pressure at 100 °C for 4h and 12 h at room
temperature. Silicone spray was used as a mold releasing agent. Here after
jute composites are designated as J-ETPUPSt, J-ETPAASt, J-ETPMASt and
glass composites as G-ETPUPSt, G-ETPAASt, G-ETPMASt. Samples with
required dimensions were machined for tensile and flexural tests. For
chemical resistance test samples of 3cm x 3cm were machined and edges
were sealed with matrix material.
Table 5.2: Fiber-matrix and compositions for jute and glass fiber composites
Composite Wt of
fabrics (g)
Wt of styrenated
resin (70%) (g)
J-ETPUPSt 122.35 85.64
G-ETPUPSt 105.67 73.96
J-ETPMASt 128.15 89.70
G-ETPMASt 110.35 77.24
J-ETPAASt 132.7 92.89
G-ETPAASt 107.61 75.32
Preparation…
164
5.5 Mechanical and electrical properties of the composites
The mechanical properties, among all the properties of plastic
materials, are often the most important properties because virtually all service
conditions and the majority of end-use applications involve some degree of
mechanical loading. Nevertheless, these properties are the least understood
by most design engineers. The material selection for a variety of applications
is quite often based on mechanical properties such as tensile strength,
modulus, elongation, and impact strength. These values are normally derived
from the technical literature provided by material suppliers. More often than
not, too much emphasis is placed on comparing the published values of
different types and grades of plastics and not enough on determining the true
meaning of the mechanical properties and their relation to end-use
requirements.
In practical applications, plastics are seldom, subjected to a single,
steady deformation without the presence of other adverse factors such as
environment and temperature. Since the published values of the mechanical
properties of plastics are generated from tests conducted in a laboratory
under standard test conditions, the danger of selecting and specifying a
material from these values is obvious. A thorough understanding of
mechanical properties, tests employed to determine such properties, and the
effect of adverse conditions on mechanical properties over a long period is
extremely important.
Plastics were considered a relatively weaker material in terms of load-
bearing properties at elevated temperatures. Therefore, the use of plastics in
electrical applications was limited to nonload-bearing, general-purpose
applications. The advent of new high-performance engineering materials has
altered the entire picture. Plastics are now specified in a majority of
applications requiring resistance to extreme temperatures, chemicals,
moisture, and stresses. The primary function of plastics in electrical
applications has been that of an insulator. This insulator or dielectric
separates two field-carrying conductors. Such a function can be served
equally well by air or vacuum. However, neither air nor vacuum can provide
any mechanical support to the conductors. Plastics not only act as effective
insulators but also provide mechanical support for field-carrying conductors.
Preparation…
165
For this very reason, the mechanical properties of plastic materials used as
insulators become very important. Typical electrical applications of plastic
material include plastic-coated wires, terminals, connectors, industrial and
household plugs, switches, and printed circuit boards.
5.5.1 Measurements
The tensile strength(ISO/R 527-1996 Type-I), flexural strength (ASTM-
D-790-2003), electric strength (IEC-60243-Pt-1-1998) and volume resistivity
(ASTM-D-257-2007) measurements were made on a Shimadzu Autograph
Universal Tensile Testing Machine, Model No. AG-X Series at a speed of
10mm/min, a high voltage tester (Automatic Electric-Mumbai) in air at 27 oC
by using 25/75mm brass electrodes and a Hewlett Packard high resistance
meter in air at 25 oC after charging for 60 sec at 500 V DC applied voltage,
respectively. Measurements were carried out in triplicate and the mean values
were considered.
5.5.2 Results and discussion
For material scientists mechanical and electrical properties are very
useful for application point of view. Tensile properties of the materials are
most widely useful for the quality characteristics of materials, while flexural
properties are useful in classification of the materials with respect to bending
strength and stiffness. Electrical properties of the materials are useful in
predicting the relative insulation quality characteristic of material selection for
specific properties with respect to combined effect of material composition
and environment. Tensile strength, flexural strength, electrical strength and
volume resistivity of jute and glass composites are presented in Table 5.3,
from which it is observed that jute composites showed moderately good
tensile and flexural properties, while glass composites showed fairly good
tensile property and moderate to fairly good flexural property. Similar behavior
is also observed in case of electrical properties of the composites.
In case of J-ETPUPSt flexural property is increased to a considerable
level, while it decreased drastically for G-ETPUPSt. Both types of composites
showed moderate tensile property and electric strength; and good volume
resistivity. G-ETPUPSt showed approximately ten times volume resistivity.
Moderately good tensile and flexural properties are mainly due to moderate
adhesion between matrix and fiber materials. Similarly low electric strength
Preparation…
166
and moderate volume resistivity of J-ETPUPSt is also due to polar free
hydroxyl groups present in jute fibers and matrix material. Moderate tensile
strength, flexural strength, and good volume resistivity of J-ETPUPSt and G-
ETPUPSt signify their importance as low load bearing housing units, in
electrical and electronic applications.
J-ETPMASt and G-ETPMASt showed respectively 1.4 and 1.3 times
more tensile strength as compared to J-ETPAASt and G-ETPAASt. Similarly
they showed respectively 2.1 and 5.7 times low flexural strength. J-ETPMASt
and G-ETPMASt showed 1.2 times electrical strength and 1.6 and 1.2 times
volume resistivity as compared to J-ETPAASt and G-ETPAASt. Thus methyl
substituent in vinyl ester reflected somewhat better mechanical and electrical
properties. This is due to different structure of the two vinyl esters and
difference in property. Mechanical and electrical properties of the composites
depend upon many facts such as nature of fibers and matrix, intrafacial
adhesion, degree of resin cure, test conditions, sample thickness, electrode
area and geometry, voltage application rate, imperfection, impurities, etc.
Moderate tensile strength, flexural strength, and good volume resistivity
signify their importance as low load bearing housing units, in electrical and
electronic applications.
Preparation…
167
Table 5.3: Mechanical and electrical properties of jute and glass composites.
Composite Tensile
strength
(MPa)
Flexural
strength
(MPa)
Electrical
strength,
(kVmm-1)
Volume
resistivity
(Ohm cm)
J-ETPUPSt 21.7 31.9 1.8 2.7 x1014
G-ETPUPSt 138.3 29.5 2.2 2.1 x1015
J-ETPAASt 12.8 7.3 1.4 2.2 x1011
G-ETPAASt 131.2 17.4 2.5 9.2 x1011
J-ETPMASt 17.7 15.6 1.7 3.5 x1011
G-ETPMASt 166.7 99.8 3.0 1.1 x1012
Preparation…
168
5.6 Chemical resistance study of composites
Chemical resistance of plastics is a complex subject. The test results
are often misinterpreted by engineers and designers. Material selection is
made without a proper understanding of the tests’ limitations and how the
results are derived. Extremely strong and tough plastic like polycarbonate has
limited applications because of its poor chemical resistance. Polypropylene,
on the other hand, has poor physical properties but is impervious to most
chemicals and solvents. The resistance of plastics to chemicals is best
understood through the study of its basic polymer structure. The type of
polymer bonds, the degree of crystallinity, branching, the distance between
the bonds, and the energy required to break the bonds are the most important
factors to consider, while studying the chemical resistance of plastic materials
[11]. For example, highly crystalline structure, lack of branching, and the
presence of very strong covalent bonds between carbon and fluorine atoms in
the main chain makes polytetrafluoroethylene resistant to almost all chemicals
and solvents. Similarly in the case of polyamides (nylons), the regular
symmetrical structure and the molecular flexibility that produces high
crystallinity and the presence of greater intermolecular forces help the
polymer to be rigid, strong, and resistant to chemicals.
Various models have been proposed for water absorption in
composites. It is well established that absorbed water in polymers and
composites plays a significant role in mechanical behavior and long term
durability. Assuming one-dimensional Fickian [12, 13] diffusion in composite,
an attempt has been made to determine diffusivity (Dx) in different
11. T. A. Richardson, Modern Industrial Plastics, Howard W. Sams and Co.,
Indianapolis, IN, p. 112, 1974.
12. Y. J. Weitsman, Fluid effects in polymers and polymeric composites,
Springer, New York, 2012.
13. T. A. Collings, Moisture absorption- Fickian diffusion kinetics and
moisture profiles. In Jones FR (ed) Handbook of polymer-fiber
composites. Horlow: Longman Scientific and Technical. 366, 1994.
Preparation…
169
environments. Diffusivity is assumed to depend only on temperature and
independent of the moisture content as well as stress levels in composites.
For one-dimensional water absorption in semi-infinite plate exposed on both
sides to same environment, the amount of water absorbed is given by Eqn.
5.1:
5.1
Where Dx = diffusivity, t = time (second) and h = sample thickness (m)
The water content in the sample at time t can be determined according to
Eqn.5.2:
5.2
Where Mt = % water absorbed at time t, Wm = weight of moist sample and Wd
= weight of dry sample. The solution of diffusion equation in terms of % water
absorption is given by eqn.5.6:
5.3
Where Mm = equilibrium water content. Diffusivity in a given environment can
be determined from the initial slope of the plot of % M against t according to
Eqn. 5.4:
5.4
In present case assuming unidimensional Fickian diffusion, water
absorption in composites was carried in distilled water, 10% of aq HCl and
10% of aq NaCl at 35 oC by a change in mass method. Pre weighed samples
were immersed in distilled water, 10% of aq HCl and 10% of aq NaCl
solutions at 35 oC. Samples were periodically taken out from the solutions,
4 mx
M tM D
h π=
( )2
2
4xm
hD slope
Mπ
=
% 100W Wm dMt Wd
−= ×
( )( )2 2
22 20
2 18 11 exp
2 1x
J
j D tG
hj
ππ
∞
=
+= − −
+ ∑
Preparation…
170
wiped with tissue papers, reweighed and reimmersed in the solutions. The
process was carried out till equilibrium was established.
The percentage weight gained by the composites in water, 10 % of aq.
HCl and 10 % of aq. NaCl solutions with the passage of time at 35oC is shown
in Figs. 5.2- 5.7. The % weight gained by each composite increased, reached
maximum and then practically remained constant, when equilibrium was
established in each of the environment. The equilibrium water content and the
equilibrium time for each of the composites in water, 10 % of aq. HCl, 10 %
aq. NaCl environments are recorded in Table 5.4. The observed trend in %
equilibrium water content in studied environments is HCl > H2O > NaCl.
Moreover practically no change in equilibrium water content is found in both
types of the composites with different vinyl esters. It is clearly observed that
water absorption in case of jute fiber reinforced composites is almost three
times than that of glass fiber reinforced composites due to large number of
polar hydrophilic –OH groups in jute fiber and matrix material. The effect of
electrolytes on water absorption is observed to some extent. The presence of
electrolytes in water affects water structure and hence water absorption
behavior as well as diffusivity of water in the composites.
Absorbed water in composites influences mechanical behavior, and
long-term durability of the polymer matrix composites. Water absorption in
composites is proved to be Fickian as well as non-Fickian in character.
Assuming one-dimensional diffusion, water absorption in semi-infinite plate
exposed to same environment was determined. Diffusivity in different
environments was determined by determining initial slope of the plot of Mt Vs
t1/2 and also summarized in Table 5.4. The solvation phenomenon is observed
in the present case, which influenced diffusivity of water in the composites.
Absorption of water in composites causes swelling of fibers till the cell walls
are saturated with water and beyond that water exists as free water in the void
structure leading to composites delamination or void formation. Absorbed
water causes weakening of the interfacial adhesion and hydrolytic
degradation of both matrix and fibers and hence deterioration of tensile
property. Cracking and blistering of fibers cause high water absorption, while
degradation causes leaching of small molecules.
Preparation…
171
Table 5.4: Water uptake and diffusivity data of glass and jute composites at 35 oC and in boiling water
Environment Equilibrium
time (h)
%, Equilibrium
water content at
35oC
Diffusivity(Dx),
10-12 (m2s-1)
% Eqm.
water
content in
boiling
water
J-ETPAASt
H2O 192 15.0 11.30 16.04
10 % aq. NaCl 168 11.87 11.70 -
10 % aq. HCl 144 15.99 11.72 -
G-ETPAASt
H2O 168 5.95 0.22 8.15
10 % aq. NaCl 144 4.61 0.27 -
10 % aq. HCl 144 6.97 0.26 -
J-ETPMASt
H2O 192 15.0 9.04 16.1
10 % aq. NaCl 168 10.9 10.56 -
10 % aq. HCl 168 16.6 11.22 -
G-ETPMASt
H2O 144 5.6 1.36 6.7
10 % aq. NaCl 168 4.4 0.95 -
10 % aq. HCl 144 6.5 0.89 -
J-ETPUPSt
H2O 144 19 9.45 19.2
10 % aq. NaCl 168 16.3 10.19 -
10 % aq. HCl 168 21.3 7.49 -
G-ETPUPSt
H2O 96 9.2 4.29 9.7
10 % aq. NaCl 168 7.2 2.90 -
10 % aq. HCl 144 10.4 3.00 -
Preparation…
172
Fig. 5.2. The plots of percent weight gain against time for J-ETPAASt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35 oC.
Fig. 5.3. The plots of percent weight gain against time for G-ETPAASt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35 oC.
Preparation…
173
Fig. 5.4. The plots of percent weight gain against time for J-ETPMASt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35 oC.
Fig. 5.5. The plots of percent weight gain against time for G-ETPMASt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35oC.
Preparation…
174
Fig. 5.6. The plots of percent weight gain against time for J-ETPUPSt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35 oC.
Fig. 5.7. The plots of percent weight gain against time for G-ETPUPSt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35 oC.
Preparation…
175
5.7 Water absorption in boiling water
Water absorption in composites mainly depends on temperature
besides presence of hydrophilic groups in composites. The percent weight
gain with the passage of time in boiling water for glass and jute composites
are presented in Figs. 5.8 and 5.9. From Table 5.4, it is clear that equilibrium
time is reduced to 28 times in case of J-ETPMASt, G-ETPMASt and J-
ETPAASt while equilibrium time decreased to 21 times in case of G-ETPAASt
and 29 times in case of J-ETPUPSt, while equilibrium time decreases to 16
times in case of G-ETPUPSt in boiling water as compared to 35 oC. Moreover
all the composites showed excellent hydrolytic stability even in harsh acidic
and saline environments confirming their applications in the field of marine.
Preparation…
176
Fig. 5.8. The plots of percent weight gain against time for J-ETPMASt, G-ETPMASt, J-ETPAASt and G-ETPAASt in boiling water.
Fig. 5.9. The plots of percent weight gain against time for J-ETPUPSt and G-ETPUPSt in boiling water.
0
2
4
6
8
10
12
14
16
18
0 2 4 6 8 10 12 14
% W
t. C
han
ge
Time/ h
J-ETPMASt
G-ETPMASt
G-ETPAASt
J-ETPAASt
0
5
10
15
20
0 5 10 15
% W
t. C
han
ge
Time /h
J-ETPUPSt
G-ETPUPSt