3.2. Impact strength and toughening mechanism
The effect of TBT concentration on the impact strength of PLA/
PBAT blends is illustrated inFig. 4, and the impact strength of pure
PLA is also presented for comparison. The impact strength is increased from 3 kJ/m
2
for pure PLA to 5 kJ/m
2
for the uncompatibilized PLA/PBAT blends. The toughness of blends is improved
prodigiously at 0.2 wt.% TBT and below, and the impact strength
of blends containing 0.2 wt.% TBT is increased by 76% as compared
to pure PLA. However, the toughness of blends has almost no
improvement with the further increasing TBT loading level. This
result is in good agreement with that of literature [11]. Zhang
et al.[11] observed that the impact strength of PLA/PBAT blends
suddenly increased at 1 wt.% of T-GMA and then trended to be saturated. However, with further addition of T-GMA beyond optimum
amount range, the impact strength gradually decreased.
The impact-fractured surface was observed using SEM, and the
corresponding micrographs were shown inFig. 5(white particles
are the PBAT phase in blends). As compared with the apparent brittle fractured surface of pure PLA, a rough surface is found for PLA/
PBAT blend. Some large and non-uniformly distributed PBAT phase
and black cavities are observed for LBT-0 specimen. The occurrence
of black cavities can be left by expunging of the dispersed PBAT
particle phase from the PLA matrix, and the interface between
PLA and PBAT is distinct. This phenomena indicates that PLA and
PBAT is immiscible at high PBAT content. These findings are consistent with the observation reported in the previous literature [9].
Yeh et al.[9] reported that many demarcated phase-seperated