Fig. 3 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 during
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 agglomeration
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.