**3.1 Storage modulus (E′)**

The results in **Figures 1– 3** for control, 14P and 28P samples, respectively, demonstrated the trademark drop in modulus around the first transition stage from elastic to viscous of the composite which can be ascribed to energy release with gradual increase in temperature [32]. Values of storage modulus recorded for the polymers at the point of interest were: Control Sample (CS)—913.18, 984.18 and 979.94 MPa; 14P—505.54, 492.47 and 473.60 MPa and, 28P—282.25, 298.70 and 285.36 MPa at 2, 5 and 10 Hz, respectively.

The values of E′ for the CS (**Figure 1**) increased with the frequency until 5 Hz and a slight decrease is observed at 10 Hz, while values of E′ for 14P sample (**Figure 2**) decreased with frequency until the highest frequency of 10 Hz. In addition, values of E′ for 28P samples (**Figure 3**) increased with the frequency and a slight decrease is observed at 10 Hz. A possible explanation for these are: for the control sample, the tendency of an increase in E′ under a higher frequency and comparatively lower value of E′ for composite subjected to 10 Hz, can be ascribed to increase in molecular mobility of the polymer chains in the first solid

**39**

**Figure 3.**

**Figure 2.**

*Dynamic Mechanical Behaviour of Coir and Coconut Husk Particulate Reinforced Polymer…*

state transition phase [33]. The continued decrease of storage modulus for the 14P sample can be ascribed to a gradual degradation of the storage modulus due to the influence of exposure to the acidic environment which causes a reduced grip of the tightly bound polymer molecules, allowing them to flow more as compared to polymer molecules in the control sample. It also means at every point of frequency variation, there was an increase in molecular dynamics of the polymer chains because the molecules can move with the force which results in a decline in storage modulus. A similar trend of storage modulus variation at each point of frequency change as observed for the control sample was noticed for the 28P sample. However a decrease in the storage modulus was observed at every corresponding frequency variation, which further explains the effect of exposure to acidic environment

*Storage modulus curves of 28P sample under varying frequencies.*

*Storage modulus curves of 14P sample under varying frequencies.*

*DOI: http://dx.doi.org/10.5772/intechopen.82889*

**Figure 1.** *Storage modulus curves of control sample under varying frequencies.*

*Dynamic Mechanical Behaviour of Coir and Coconut Husk Particulate Reinforced Polymer… DOI: http://dx.doi.org/10.5772/intechopen.82889*

**Figure 2.** *Storage modulus curves of 14P sample under varying frequencies.*

**Figure 3.** *Storage modulus curves of 28P sample under varying frequencies.*

state transition phase [33]. The continued decrease of storage modulus for the 14P sample can be ascribed to a gradual degradation of the storage modulus due to the influence of exposure to the acidic environment which causes a reduced grip of the tightly bound polymer molecules, allowing them to flow more as compared to polymer molecules in the control sample. It also means at every point of frequency variation, there was an increase in molecular dynamics of the polymer chains because the molecules can move with the force which results in a decline in storage modulus. A similar trend of storage modulus variation at each point of frequency change as observed for the control sample was noticed for the 28P sample. However a decrease in the storage modulus was observed at every corresponding frequency variation, which further explains the effect of exposure to acidic environment

*Fillers - Synthesis, Characterization and Industrial Application*

acid solution was used as control.

**3. Results and discussion**

285.36 MPa at 2, 5 and 10 Hz, respectively.

*Storage modulus curves of control sample under varying frequencies.*

**3.1 Storage modulus (E′)**

of 14 and 28 days (14P and 28P) were considered. The sample not exposed to the

Dynamic mechanical analysis (DMA) was used to investigate the viscoelastic properties of the exposed polymer samples as reported in our previous study [30]. The frequencies under which DMA measurements were made in this study are: 2, 5 and 10 Hz. The loss and storage moduli at low temperatures where polymer molecules are tightly compressed and where the first solid-state transitions occur were analyzed.

The results in **Figures 1– 3** for control, 14P and 28P samples, respectively, demonstrated the trademark drop in modulus around the first transition stage from elastic to viscous of the composite which can be ascribed to energy release with gradual increase in temperature [32]. Values of storage modulus recorded for the polymers at the point of interest were: Control Sample (CS)—913.18, 984.18 and 979.94 MPa; 14P—505.54, 492.47 and 473.60 MPa and, 28P—282.25, 298.70 and

The values of E′ for the CS (**Figure 1**) increased with the frequency until 5 Hz and a slight decrease is observed at 10 Hz, while values of E′ for 14P sample (**Figure 2**) decreased with frequency until the highest frequency of 10 Hz. In addition, values of E′ for 28P samples (**Figure 3**) increased with the frequency and a slight decrease is observed at 10 Hz. A possible explanation for these are: for the control sample, the tendency of an increase in E′ under a higher frequency and comparatively lower value of E′ for composite subjected to 10 Hz, can be ascribed to increase in molecular mobility of the polymer chains in the first solid

**2.2 Dynamic mechanical properties of corroded polymer specimens**

**38**

**Figure 1.**

to which the degradation in the fiber/filler/matrix interface can be ascribed, and subsequently allows tightly bound molecules to move with the applied force and cause a decline in the ability of the composite to store energy.
