Cao
su tổng hợp được phát minh để cải thiện các khuyết điểm của cao su thiên nhiên,
đáp ứng nhiều ứng dụng thực tế khắc nghiệt. Cao su chloroprene (neoprene hoặc
CR) là một trong những loại cao su tổng hợp thông dụng. Tính chất hóa lý chung
của cao su chloroprene được trình bày sau đây.
…
The
properties discussed here are attainable with neoprene but may not necessarily
be incorporated into every neoprene product. Nor will every neoprene product
perform the same in all environments. The reason for this variation is
compounding. By selective addition and/or deletion of specific ingredients
during compounding, specific properties can be enhanced or reduced to provide
the neoprene formulation best suited for the application. A neoprene compound
can be produced that will provide whichever of the properties discussed are
desired. When the hardness of neoprene is above 55 Shore A, its resilience exceeds that
of natural rubber by approximately 5%. At hardnesses below 50 Shore A, its
resilience is not as good as that of natural rubber, even though its resilience
is measured at 75%, which is a
high value. Because of its high resilience, neoprene products have low
hysteresis and a minimum heat buildup during dynamic operations.
Solid
neoprene products can be ignited by an open flame but will stop burning when
the flame is removed. Because of its chlorine content, neoprene is more
resistant to burning than exclusively hydrocarbon elastomers. Natural rubber
and many of the other synthetic elastomers will continue to burn once ignited,
even if the flame is removed. In an actual fire situation, neoprene will burn.
Although compounding can improve the flame resistance of neoprene, it cannot
make it immune to burning.
Compared
to natural rubber, neoprene is relatively impermeable to gases. Table 4.9 lists
typical permeability constants. Because of this impermeability, neoprene can be
used to seal against Freon blowing agents, propane, butane, and other gases.
Neoprene
is used in many electrical applications, although its dielectric
characteristics limit its use as an insulation to low voltage (600V) and low
frequency (60Hz). Because of its
high degree of resistance to indoor and outdoor aging and its resistance to
weathering, neoprene is often used as a protective outer jacket to insulation
at all voltages. It is also immune to high-voltage corona discharge effects
that cause severe surface cutting in many types of elastomers.
…
Trích
đăng từ sách Mechanical and
Corrosion-Resistant Properties of Plastics and Elastomers, Philip A. Schweitzer, CRC Press, 2000,
trang 281 – 282
(vtp-vlab-caosuviet)
