The holes may form in two ways: one is by NR
particles exfoliating when fracture the specimen, the other is by the
hydrolysis just like PLA. Apart from some holes and NR particles,
some tubular channels can also be observed from fracture surface
of 20 days hydrolyzed PLA/NR-5 specimen. This indicates that the
holes may develop gradually and become channels which can
connect external environment of the specimens with the hydrolysis
time. Therefore, the surfaces of the specimens having some
microporous are found after 20 days hydrolysis. Furthermore, the
samples become brittle after a week hydrolysis and aggravate with
the progress of hydrolysis, which can also be ascribed to the generation
of holes entire the bulk and the following development of
holes.