Biomedical Engineering Reference
In-Depth Information
60
CO
i
20.7
6.4
4.6
2.3
50
40
30
20
10
0
0
30
60
90
120
150
Incubation time (days)
Figure 16.5
Mineralization profi les of thermally oxidized LDPE materials having different
levels of oxidation in aqueous respirometric tests.
the same products made without the prodegradant additives. The oxo-biodegradable
technology adds yet another desirable characteristic to the long list of useful prop-
erties for which the polyolefi ns are well known. This technology also provides
environmental benefi ts at nominal extra cost that consumers would like to support
but are usually reluctant to pay much of a premium for.
In many countries there are formal as well as informal programs for recycling
postconsumer plastics. The recycling of used plastics can be a signifi cant chal-
lenge, [47] but it is an important part of striving for a sustainable society. It is
signifi cant therefore to note that EPI's TDPA-PE materials, in spite of being oxo-
biodegradable, can be recycled with regular PE recycling operations. This is
because the prodegradants involved are not just simple oxidizing agents. The
former do not affect the properties of the plastic until something else, for example,
heat or UV light, initiates oxidative degradation, and this will not occur until all
the antioxidants are consumed.
16.6
Concluding Remarks
For a number of decades, the polyolefi ns have been among the most useful and
versatile materials. This is because they have a wide variety of desirable properties
and are relatively inexpensive. In order to provide for years of reliable service,
especially outdoors, it has been necessary to determine the kinetics and mecha-
nisms by which polyolefi ns lose their useful properties over time, that is, to elu-
cidate the details of oxidative degradation. On the basi
s
of this fundamental
