Biomedical Engineering Reference
In-Depth Information
To prove the hypothesis experiments were conducted to measure the change in the
molecular mass and
physical-mechanical properties
(σ, ʵ) of the polymer compositions
within a long-time exposure to the fungi (their aggressive metabolites). Penicillium
cyclopium and Aspergillus terreus were opted as micromycetees-biodegraders which are most
active for grafted and block-copolymers of chitosan with methylacrylate. Both the direct
effect of exometabolites (when the fungi were cultivated on the polymers) and indirect one
(the effect of metabolism products of the fungi) were studied. The experiment longevity was
20 weeks. The physical-mechanical properties of the films based on grafted and block
copolymers of chitosan with MA and molecular mass distribution of PMA chains in
(co)polymers were measured on the 2
nd
, 4
th
, 6
th
, 12
th
and 20
th
exposition weeks. The results
are shown in the tables 5, 6 and figure 1 - 2. Tables 5, 6 display that in case with both the
grafted and block copolymers there observed a decline of physical-mechanical properties -
failing stress and break strain which testifies to the biodegradation of the polymers. In control
tests these properties do not change. It is disclosed that the reaction of the compositions to the
exposition to various fungi species Penicillium cyclopium, Aspergillus terreus and their
metabolism products differs considerably. The declining of the stress-strain properties of the
block-copolymers (table 5) under the effect of Aspergillus terreus unvaries within the whole
experiment period (20 weeks), and the films almost completely lose their plasticity (the
sample was placed on the fungi culture).
Table 5. The dependence of the change of the physical-mechanical properties of films of
hybrid block-copolymer CHITOSAN-МА from the time of fungus A.terreus effect.
([МА]/[ glycosamine]= 3,3 mole/base-mole.)
σ, МPa
ʵ, %
The films were
placed under the
agar medium of the
fungi culture
The films
were placed
on the fungi
culture
The films were
placed under the
agar medium of
the fungi culture
The films
were placed
on the fungi
culture
Time,
weeks
control
control
0
36,0
36,0
36,0
17,0
17,0
17
4
37,0
29,5
21,7
20,0
6,8
3,6
6
33,6
28,6
18,7
18,0
5,0
3,1
12
36,8
28,6
11,9
17,0
2,6
3,3
20
35,9
28,0
-
16,0
3,2
-
Table 6. The dependence of the change of the physical-mechanical properties of films of
the hybrid grafted copolymer CHITOSAN-МА from the time of fungus P.cyclopium
effect ([МА]/[ glycosamine]= 3,3 mole/base-mole)
σ, МPa
ʵ, %
Time,
weeks
The films were
placed on the fungi
culture
The films were
placed on the fungi
culture
control
Suspension
control
Suspension
0
32,0
32,0
32,0
18,0
18,0
18,0
2
29,0
-
29,0
19,0
-
28,0
4
28,9
26,4
28,9
20,0
37,9
26,0
6
27,0
22,1
22,0
19,0
7,6
7,0
20
26,0
23,3
19,0
18,1
7,3
8,0
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