Chemistry Reference
In-Depth Information
PVC is used in a variety of applications from rigid applications such as pipe
and vinyl siding to flexible applications such as black electrical tape, garden
hoses, and tubing. The flexibility is imparted by plasticizers. A plasticizer
is an additive that reduces intermolecular forces in polymers and makes the
polymer more flexible [6]. More than 12 billion pounds of plasticizers are sold
globally each year, with 96% used to impart flexibility to PVC [7]. There are
many types of plasticizers, but commonly they are esters such as esters of
adipic acid, trimellitic acid, or phthalic acid.
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Adipate esters
Phthalate esters
Trimellitate esters
Dioctyl phthalate (DOP), more properly called di-2-ethylhexyl phthalate
(DEHP), is commonly used as an inexpensive general purpose plasticizer.
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DOP
These plasticizers have been used for more than 50 years in applications
such as IV bags and other medical devices. However, there is some uncer-
tainty and debate within the scientific community about possible health
effects, especially with DOP. To date, no studies have evaluated the potential
for DOP to cause cancer in humans. Eating high doses of DOP for a long
time resulted in liver cancer in rats and mice. The U.S. Department of Health
and Human Services has determined that DOP may reasonably be anticipated
to be a human carcinogen. EPA has determined that DOP is a probable
human carcinogen. These determinations were based entirely on liver cancer
in rats and mice. The International Agency for Research on Cancer (IARC)
has recently changed its classification for DOP from "possibly carcinogenic
to humans" to "cannot be classified as to its carcinogenicity to humans,"
because of the differences in how the livers of humans and primates respond
to DOP as compared with the livers of rats and mice [8].
The choice of plasticizer is based upon many factors and depends upon the
end-use application. Cost, flexibility imparted per pound of plasticizer, low
temperature performance, volatility, and other factors are commonly impor-
tant in the selection process.
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