Cao
su butyl là loại cao su tổng hợp khá thông dụng, nhưng lượng dùng thấp hơn các
loại cao su tổng hợp khác như NBR, SBR, EPDM. Cao su butyl được sử dụng chủ yếu
trong các ứng dụng yêu cầu các tính chất đặc trưng của nó như tính không thấm
khí, khả năng hấp thu năng lượng cơ học cao. Phần tài liệu sau trình bày chung về
tính chất và ứng dụng của cao su butyl.
…
The
single outstanding physical property of butyl rubber is its impermeability. It
does not permit gases like hydrogen or air to diffuse through it nearly as
rapidly as ordinary rubber does, and it has excellent resistance to the aging
action of air. These properties make butyl rubber valuable in the production of
life jackets (inflatable type), life rafts, and inner tubes for tires.
At
room temperature, the resiliency of butyl rubber is poor, but as the
temperature increases, the resiliency increases. At elevated temperatures,
butyl rubber exhibits good resiliency. Its abrasion resistance, tear
resistance, tensile strength, and adhesion to fabrics and metals is good. Butyl
rubber has a maximum continuous service temperature of 250-350°F (120-150°C)
with good resistance to heat aging. Its electrical properties are generally
good but not outstanding in any one category. The flame resistance of butyl rubber
is poor.
The
polymer has excellent flexibility but very low resilience due to its molecular
structure. As a result, it absorbs a great deal of any mechanical energy that
is put into it. This energy absorption is responsible for butyl rubber’s
vibration-damping properties, which are maintained over a broad temperature
range. Consequently, butyl rubber is an excellent choice where high vibration
damping is required. This property is useful in automobile body mounts and
suspension bumpers.
Table
4.15 lists the physical and mechanical properties of butyl rubber.
There
are two commercially available halogenated butyl rubber derivatives bromobutyl
(BIIR) and chlorobutyl (CIIR). The halogen atoms are incorporated into the
polymer on the isoprene units. These compounds have chemical properties that
permit the polymers to be covulcanized with other elastomers more readily than
IIR. The end-use properties and applications are similar to those for IIR. A
typical application is the cover for air conditioning hoses.
Chlorobutyl
(CIIR) rubbers have a maximum operating temperature of 300°F (150°C) and can be
operated as low as -30°F (-34°C). The other physical and mechanical properties are similar to those of butyl rubber.
…
Trích
đăng từ sách Mechanical and Corrosion-Resistant
Properties of Plastics and Elastomers,
Philip A. Schweitzer, CRC Press, 2000, trang 295 – 299
(vtp-vlab-caosuviet)
