Figure 12 shows the weight loss
of LDPE/TPS40 blends exposed to activated sludge as a function of degradation time. As
expected, raw PE1 remains unchanged after 45 days. On the contrary, raw TPS40 is
completely consumed within 21 days of exposure. For the LDPE/TPS40 blends, the
maximum biodegradation extent is observed at times longer than the raw TPS40. If TPS40
particles are present only on the surface, and not interconnected with particles inside the
LDPE/TPS40 blends, then it could be expected that starch domains would be completely
biodegraded like the raw TPS40. Percent continuity observed in Figure 10 shows that TPS40
particles are interconnected one to another. At TPS40 concentration of about 30%,
interconnection increases when the morphology of starch domains changes from spherical
(PE2/TPS40 blend) to fiber-like particles (PE1/TPS40 blend). The extent of biodegradation
of TPS40 at 45 days of extraction for PE1/TPS40 blends at 62%, 32% of TPS40 and
PE2/TPS40 (69:31) were 92%, 39% and 22%, respectively. However, when the maximum
biological extraction is compared with the maximum enzymatic degradation, important
difference is noticeable, especially in blends with ca. 30 wt% TPS40.