In comparison with that of control specimen at room temperature
(25 C), the tensile strength was reduced by 25.8% for the increment
of temperature from 25 C to 50 C, 41.2% for increment of
temperature from 25 C to 60 C, and 63.1% for increment of temperature
from 25 C to 70 C, respectively. The tensile modulus of
elasticity reduced significantly 42.6% when the temperature was
increased from 25 C to 60C and 64.9% when the temperature
was increased from 25 C to 70 C. These results indicate that both
tensile strength and tensile modulus of elasticity of WPVC composites
were temperature dependence. However, the tensile strength
was found to be more sensitive to the temperature change than
that of tensile modulus of elasticity since the tensile strength is
the property of material under high loading or under large deformation.
The similar behaviors that higher temperature affects on
mechanical strength more than that of mechanical modulus of
elasticity were also found in case of natural woods [17,18]. The
temperature effect on mechanical properties was also found in
case of wood polypropylene (wood/PP) composites as shown in
[7,8]. Therefore, changes in normalized MOR and MOE as temperature
increment of WPVC composites in comparison with those
obtained from previous works in wood/PP composites [7,8] are
shown in Figs. 2 and 3. These results indicate that the changes in
normalized MOR and MOE of WPVC composite were lower than
those of wood/PP composites for the temperatures in the range
of 25 C to 50 C but they significantly decreased for the temperatures
in the range of 60 C to 70 C. The decrement of the mechanical
properties of WPVC composites, which was higher than wood/
PP composites for the temperatures in the range of 60 C to 70 C,
can be described by the softening temperature of PVC material
which is typically lower than PP material. Also, the temperatures
in the range of 60 C to 70 C are very close to the glass transition
temperature of PVC material [24]. Finally, the empirical models
presenting normalized MOR and MOE as a function of temperatures
are obtained by using a curve fitting method. The models
are presented in Fig. 4. They can be used to predict the tensile
properties of WPVC composites at specified temperature.