shows the effect of MCC loading on elongation at break. It can be clearly seen that the elongation at break decreased gradually as the MCC concentration is increased for all PLA/MCC formulations. These observations may be attributed to the stiffening action of the filler by restricting the segmental chain movement of PLA dur- ing tensile testing. According to Pei, Qi, and Berglund (2005), the elongation at break is affected by the volume fraction of the added reinforcement, the dispersion of the reinforcement in the matrix, and the interaction between the reinforcement and the matrix. MCC displayed poor interaction and dispersion in PLA matrix due to higher tendency to agglomerate. This cause substantial local stress concentrations and reduced the elongation at break (Cheng, Wang, & Rials, 2009). Further evidence on the dispersion and agglomer- ation of MCC particles in the PLA matrix is given in SEM analysis, which will be discussed in detail in the next section. From the above results and discussion it can be concluded that, increased MCC contents have a negative effect on PLA/MCC composites strength as compared to the pure PLA due to the agglomeration of MCC particles.