Effects of Gamma Radiation on the Physicochemical Properties …
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properties; chemical and corrosion resistance; thermal stability; good electrical conductivity; easy processability, durability, as well as low density and cost. Reinforced
polyester resins have been used in household products, biomedical applications,
building materials, automotive and aircraft industry, spacesuits and sports goods.
In a study, a polyester base composite was elaborated adding raw jute fabrics (a
lingo-cellulosic fiber crop), by the heat-press molding technique. It was composed
of three layers of jute fabrics and polyester resin mixed with cross-linking agents.
Such composites were irradiated from 2 to 14 kGy, for the complete cross-linking of
the polyester resin. The results show high degree of cross-linking and morphological
changes on the surface of the composites as well as highest improvements on the
physical and mechanical properties when they were irradiated at 10 kGy. In particular,
the tensile strength increase from 60 to 90 MPa, and the flexural strength from 92
to 154 MPa. As it is known, the higher stiffness of the raw jute fabric is due to the
higher lignin content, this imparts higher tensile strength and tensile modulus to the
composite [33].
As higher the values of tensile and flexural strength, more stiffness and low flexibility is obtained. In the case of irradiated composites, the tensile modulus increase
from 1.8 to 2.9 GPa, the flexural modulus from 3.1 to 5 GPa, but they showed low
flexibility; such results may be attributed as the increased in cross-linking extend
in the matrix by irradiation, which made the composites more ductile. Moreover,
the surfaces of the composite (analyzed by AFM), showed smoother morphology
for non-irradiated composites, instead of those for irradiate ones. Radiation induces
highly dense cross-linking in the matrix, which improve the compactness and increase
the roughness of the surfaces [33].
Composites elaborated with unsaturated polyester resin and marble show changes
on their morphologies, according to irradiation gamma dose. In Fig. 4, SEM images
of non-irradiated composites show a smooth and homogeneous surface with some
marble particles covered by polyester resin, but after irradiating with gamma rays,
morphological changes are obtained, the polyester resin shrinks and the marble particles agglomerate. More detachable particles are obtained and the presence of small
cavities less than 10 μm are observed.
Composites with polyester resin and jute treated fabric, were elaborated by hand
lay-up and heat press molding techniques. After, they were irradiated from 2 to
9 kGy. The results show, the highest improvements at 5 kGy of irradiation dose. The
tensile strength improves 31%, while the bending strength 26%, and impact strength
12%, such values respect to the values for non-irradiated composites. Such increase
may be due to the intercross-linking between the neighboring cellulose molecules,
which resulted in the strength of natural fiber. But at higher irradiation dose, the
main chain may be broken down and polymer may degrade into fragments and, as a
result, mechanical properties will decrease. Nevertheless, low water uptake as well as
higher moisture resistance of jute polyester composites are ideal for roofing and wall
cladding in industrial building. Moreover, they can primarily be used for low-cost
housing and automotive interior component applications [34].
Composites elaborated with polyester resin (50%) and PET fibers were elaborated
by hand lay-up and compression molding process. After they were irradiated with
25
properties; chemical and corrosion resistance; thermal stability; good electrical conductivity; easy processability, durability, as well as low density and cost. Reinforced
polyester resins have been used in household products, biomedical applications,
building materials, automotive and aircraft industry, spacesuits and sports goods.
In a study, a polyester base composite was elaborated adding raw jute fabrics (a
lingo-cellulosic fiber crop), by the heat-press molding technique. It was composed
of three layers of jute fabrics and polyester resin mixed with cross-linking agents.
Such composites were irradiated from 2 to 14 kGy, for the complete cross-linking of
the polyester resin. The results show high degree of cross-linking and morphological
changes on the surface of the composites as well as highest improvements on the
physical and mechanical properties when they were irradiated at 10 kGy. In particular,
the tensile strength increase from 60 to 90 MPa, and the flexural strength from 92
to 154 MPa. As it is known, the higher stiffness of the raw jute fabric is due to the
higher lignin content, this imparts higher tensile strength and tensile modulus to the
composite [33].
As higher the values of tensile and flexural strength, more stiffness and low flexibility is obtained. In the case of irradiated composites, the tensile modulus increase
from 1.8 to 2.9 GPa, the flexural modulus from 3.1 to 5 GPa, but they showed low
flexibility; such results may be attributed as the increased in cross-linking extend
in the matrix by irradiation, which made the composites more ductile. Moreover,
the surfaces of the composite (analyzed by AFM), showed smoother morphology
for non-irradiated composites, instead of those for irradiate ones. Radiation induces
highly dense cross-linking in the matrix, which improve the compactness and increase
the roughness of the surfaces [33].
Composites elaborated with unsaturated polyester resin and marble show changes
on their morphologies, according to irradiation gamma dose. In Fig. 4, SEM images
of non-irradiated composites show a smooth and homogeneous surface with some
marble particles covered by polyester resin, but after irradiating with gamma rays,
morphological changes are obtained, the polyester resin shrinks and the marble particles agglomerate. More detachable particles are obtained and the presence of small
cavities less than 10 μm are observed.
Composites with polyester resin and jute treated fabric, were elaborated by hand
lay-up and heat press molding techniques. After, they were irradiated from 2 to
9 kGy. The results show, the highest improvements at 5 kGy of irradiation dose. The
tensile strength improves 31%, while the bending strength 26%, and impact strength
12%, such values respect to the values for non-irradiated composites. Such increase
may be due to the intercross-linking between the neighboring cellulose molecules,
which resulted in the strength of natural fiber. But at higher irradiation dose, the
main chain may be broken down and polymer may degrade into fragments and, as a
result, mechanical properties will decrease. Nevertheless, low water uptake as well as
higher moisture resistance of jute polyester composites are ideal for roofing and wall
cladding in industrial building. Moreover, they can primarily be used for low-cost
housing and automotive interior component applications [34].
Composites elaborated with polyester resin (50%) and PET fibers were elaborated
by hand lay-up and compression molding process. After they were irradiated with