3.3. Mechanicalproperties
The effects of MCC loading on the tensile properties of pure PLA and PLA/MCC composites are shown in Fig. 3. As can be seen in Fig. 3, incorporation of MCC into the PLA matrix did not show any improvements in both tensile strength and elongation at break of the composites as compared to pure PLA. However the Young’s modulus was increased from 3.9 GPa to 4.6 GPa with increased MCC loading. The increase in modulus with increasing MCC loading in PLA can be explained by increased in hydrogen bonding, stiffening effect and high crystallinity index of the filler which is a typical characteristics filler/polymer composites (Cheng, Wang, & Rials, 2009). As reported in our previous paper, the relative crystallinity index of MCC obtained was 87% of cellulose I which may have also contributed to the increase in theYoung’s modulus of PLA/MCC composites (Kemala, Budianto, & Soegiyono, 2012).