**3.2 Loss modulus (E″)**

The results in **Figures 4**–**6** for control, 14P and 28P samples, respectively, show that upon frequency variation, the values of loss modulus (E″) decreased, but an exception was noticed in this trend for the 14P sample. Values of loss modulus recorded for the polymers at low temperatures where the molecules are still

**Figure 4.** *Loss modulus curves of control sample under varying frequencies.*

**41**

**4. Conclusions**

**Figure 6.**

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

tightly compressed and the region of first solid state transitions were: CS—113.32, 109.43 and 107.62 MPa; 14P—92.92, 92.92 and 101.93 MPa and 28P—46.08, 45.61 and 45.18 MPa at 2, 5 and 10 Hz, respectively. These results indicate that the acid solution provoked degradation in the fiber/filler/matrix interface which may be associated with the occurrence of fractures under stress conditions. These results corroborates findings of Stamenović et al. [22], which suggested that the most significant influence of corrosive solutions was on the fiber-matrix connection and

The possible pathways for the reduction in storage and loss moduli after exposure to the acidic environment can be explained or associated with the penetration and absorption that occurred between the acid solution and the composite constituents (matrix, filler and fiber). The solution most likely penetrates through the polymer matrix and has the possibility of separating out in micro-cracks. These assertions have also been buttressed by [31, 34]. Also similar pathways can be attributed to the degradation of the fiber/filler/matrix interface which is caused by the penetration of the acid solution through cracks which may have gained entry through voids in the matrix [17, 22, 35]. According to Hammami and Al-Ghilani [36], the degradation of the mechanical properties of polymers can occur in two stages. Firstly, the polymer is degraded under actions which are as a result of the diffusion of water and the presence of hydrogen ions. Secondly, the fiber itself can be degraded which results to cracks appearing on the surface of the fiber. This to some extent affects the resistance of the composite to stresses. Moreso, according to Stamenović et al. [22], a degradation of the mechanical properties can be associated with the fiber-matrix interface where the acid immersion of the composites promotes the deficiencies of the stress carrying capacity of the polymer composites.

The dynamic mechanical properties of coir and coconut husk particulate reinforced composites immersed in an acid solution over periods of 14 and 28 days

this influence directly reduces the load carrying capacity of composites.

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

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

**Figure 5.** *Loss modulus curves of 14P 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 6.** *Storage modulus curves of 28P sample under varying frequencies.*

tightly compressed and the region of first solid state transitions were: CS—113.32, 109.43 and 107.62 MPa; 14P—92.92, 92.92 and 101.93 MPa and 28P—46.08, 45.61 and 45.18 MPa at 2, 5 and 10 Hz, respectively. These results indicate that the acid solution provoked degradation in the fiber/filler/matrix interface which may be associated with the occurrence of fractures under stress conditions. These results corroborates findings of Stamenović et al. [22], which suggested that the most significant influence of corrosive solutions was on the fiber-matrix connection and this influence directly reduces the load carrying capacity of composites.

The possible pathways for the reduction in storage and loss moduli after exposure to the acidic environment can be explained or associated with the penetration and absorption that occurred between the acid solution and the composite constituents (matrix, filler and fiber). The solution most likely penetrates through the polymer matrix and has the possibility of separating out in micro-cracks. These assertions have also been buttressed by [31, 34]. Also similar pathways can be attributed to the degradation of the fiber/filler/matrix interface which is caused by the penetration of the acid solution through cracks which may have gained entry through voids in the matrix [17, 22, 35]. According to Hammami and Al-Ghilani [36], the degradation of the mechanical properties of polymers can occur in two stages. Firstly, the polymer is degraded under actions which are as a result of the diffusion of water and the presence of hydrogen ions. Secondly, the fiber itself can be degraded which results to cracks appearing on the surface of the fiber. This to some extent affects the resistance of the composite to stresses. Moreso, according to Stamenović et al. [22], a degradation of the mechanical properties can be associated with the fiber-matrix interface where the acid immersion of the composites promotes the deficiencies of the stress carrying capacity of the polymer composites.
