Cao
su tổng hợp SBR được phát triển trong chiến tranh thế giới II do sự thiếu hụt của
cao su thiên nhiên. Sự so sánh tính chất cơ lý của cao su thiên nhiên và cao su
SBR được trình bày sau đây.
…
In
general, Buna-S is very similar to natural rubber although some of its physical
and mechanical properties are inferior. It is lacking in tensile strength,
elongation, resilience, hot tear, and hysteresis. These disadvantages are
offset somewhat by its low cost, cleanliness, slightly better heat-aging
properties, slightly better wear than natural rubber for passenger tires, and
availability at a stable price. The electrical properties of SBR are generally
good but are not outstanding in any one area.
Because
of these shortcomings, there are many variations and blends of NR-SBR. Basic is
the ratio of butadiene to styrene, temperature of polymerization, and type of chemicals
used during polymerization. The NR-SBR blends must be properly formulated to
achieve the correct balance of properties. SBR is superior to NR in several of
its processing properties. It also has excellent abrasion resistance and
resistance to hydraulic brake fluid.
Molded
SBR parts have a strong tendency to bloom due to the presence of added
stabilizers. The bloom creates an unsightly appearance and can cause migration
staining in contact with paint. Consequently, SBR is not generally used in
readily visible locations or in contact with painted surfaces.
Buna-S
has a maximum operating temperature of 175°F (80oC), which is not
exceptional. At reduced temperatures below 0oF, Buna-S products are
more flexible than those produced from natural rubber.
Butadiene-styrene
rubber has poor flame resistance and will support combustion.
…
Trích
đăng từ sách Mechanical and Corrosion-Resistant
Properties of Plastics and Elastomers,
Philip A. Schweitzer, CRC Press, 2000, trang 289 – 291
(vtp-vlab-caosuviet)
