## 3 Results and Discussion
### 3.2. Mechanical Analysis
#### 3.2.2 Tensile Modulus of Elasticity  
The control sample of PA6 for tensile modulus of elasticity (TMOE) test had a value of 3.01 GPa. The control sample subjected to elongation initially responded with elastic deformation, viscoelasticity followed by the yield point. The samples were allowed to deform after yielding resulting in necking and propagation of necking until fracture to measure the elongation at break. The TMOE increased significantly for the composites and its increase is linear to increase in cellulose composition. The maximum TMOE was obtained for 25% composition samples with their values being 4.6 GPa and 4.4 GPa for dry and 48-h conditioned samples respectively (Figure 8b). These TMOE values are equivalent to 53% higher than those of the control sample. The incorporation of cellulose pulp fibers into PA6 matrix restricts the elastic deformation of PA6 resulting in composites with high TMOE [14; 46]. Due to this, pulp cellulose-PA6 composites when subjected to tensile load displayed notably lower strains at yield point when compared to the control sample. The significant drop in strain levels at break is shown in Figure 8a. Higher compositions of cellulose pulp fibers contribute to more relative surface area for the PA6 matrix to adhere to, owing to the high dispersion and distribution of fibers within the matrix imparted during Gelimat compounding. Thereby, forming stronger interfacial bonds and incidentally increasing the tensile strength and TMOE [47; 48].  
There was a slight decrease of tensile strength from 66.17 MPa to 64.76 MPa from 20% to 25% cellulose composition for the dry samples and 59.40 MPa to 57.29 MPa from 15% to 25% composition for 48-h conditioned samples. Though these were small decrease in the values, this may be due to lack of wetting and interaction between the fibers and PA6 matrix [14]. In such cases, the lack of interaction weakens the reinforcing effect of the fibers within the PA6 matrix [49]. The reinforcing effect remain dominant for TMOE and improvements were seen linearly with increase in composition (Figure 8b).  
Figure 8: (**a**) Elongation at break (indicating low strain at break for composites compared to control sample), and (**b**) Tensile modulus of elasticity plot for all compositions.  
This linear increase in stiffness depends on the fiber composition, dispersion and distribution of the pulp fibers within the PA6 matrix [50].  
Stress strain curves for control sample (neat PA6) and the different compositions of cellulose pulp-PA6 composites deduced from the experimental data are shown in Figure 9. The deformation behavior during elongation for all the samples is observed. Naturally, the presence of fibrils reduces the elongation in the composites when compared to the neat PA6 attributable to the reinforcing effect of cellulose fibers in the matrix [29]. In addition, increase in the cellulose composition supplements to stiffening the composites. Further, it can be testified from Figure 8a that as fiber composition increases, the strain at the point of deformation decreases thanks to the strong interfacial bonding between fiber and matrix.