Antibacterial Activity Test. The antibacterial activity
of PLA/PU and PLA/PU/GO nanocomposites against E.
coli ATCC 25922 andS. aureus ATCC 6538 was measured by using plastics-measurement of antibacterial activity on plastics surfaces (ISO 22196, International Standard
22196 : 2007(E)). Before the test, the film samples (PLA/PU,
PLA/PU/GO (3%) and PLA/PU/GO (5%)) were cut into
40mm×40mm and washed repeatedly with sterile water,
then driedintheair. Atthesametime,polyethylenefilms
were prepared in 40mm×40mm, sterilized in 75% ethanol,
and then washed with sterile water. 1.5 ×10
5
CFU/mL
bacterial suspension was seeded on each film sample and
covered with polyethylene film so that the bacterial sus-pensioncanspreadtotheedges.Makesurethatbacterial
suspension does not leak beyond the edges of the film. 40mL
of phosphate-buffered saline (PBS) was used to wash the
sample and polyethylene films in order to get the present
bacteria followed by gentle shaking for 1 h, thendiluted to 10-