Page 148 - Engineering Plastics Handbook

Acrylonitrile-Butadiene-Styrene (ABS) Resin 121

Although there is some difference by grade, notched Izod impact strength
of transparent ABS is about 10 to 20 kg⋅cm/cm, which is much higher
than that of poly(methyl methacrylate). In the case of polycarbonate, the
impact strength is excellent—at least 30 kg⋅cm/cm to at most greater than
60 kg⋅cm/cm. In addition, other physical properties, i.e., tensile strength
and flexural strength, are also very high. However, since polycarbonate has
poor processability in spite of excellent impact, tensile, and flexural
strength, its application field is limited. There is a difficulty in using poly-
carbonate products for injection products having a complicated structure
or large injection products. Different from other transparent resins, trans-
below –40°C.
parent ABS is a resin comprising the rubber phase, having T g
Therefore, transparent ABS exhibits ductile properties provided by the
rubber phase and has relatively low rigidity, tensile strength, flexural
strength, etc. In comparison to other transparent resins, the tensile
2
strength is in the range of 350 to 550 kg/cm , and flexural strength is in
2
the range of 500 to 850 kg/cm . Thus, as the rubber content is increased,
tensile strength and flexural strength are decreased.
One of the most important advantages of transparent ABS is easy
processability. Since transparent ABS has a processing temperature of
about 210° and therefore can be readily processed by the general extru-
sion and injection, it has been used in various application fields. However,
transparent ABS has the disadvantage that its optical properties are infe-
rior to those of poly(methyl methacrylate) or polycarbonate because they
are composed of a single component, and therefore have excellent optical
properties. In transparent ABS, since the transparency is provided by
controlling the refractive index of the matrix phase to be consistent with
the refractive index of the rubber phase, there is a limit to the trans-
parency. Since the refractive index is altered by monomers swelled on the
rubber phase, it is difficult to make the refractive index of the matrix
phase completely correspond to that of the rubber phase, resulting in a high
haze. Although the haze value is being lowered as the technology is devel-
oped, transparent ABSs have mostly a haze value in the range of 1.5 to 2.5.
Before the year 2000, the transparent ABS business was not on a
large scale, and no intense competition was present in the market.
However, as it has been recognized that the transparent ABS is rais-
ing more concerns than other ABS resins, the number of companies
that concentrate on the transparent ABS business have increased. To
comply with such commercial situations and consumer demand, the
transparent ABS makers concentrate their effort on the development
of various grade products. The initial market of transparent ABS con-
centrates on the high-rigid-grade products having a notched Izod
impact strength of about 10 kg⋅cm/cm, and the high-impact-strength
grade products having an impact strength of 15 to 20 kg⋅cm/cm have
been developed. Much functionality is added to introduce various