Page 147 - Engineering Plastics Handbook

120 Engineering Plastics

equation can be consistent with the refractive index of the rubber used as
the core. Although the composition is varied depending on the kinds of
rubber used as the core and the mechanical properties required for the final
product, it is usually in the ratio of methyl methacrylate/acrylonitrile/buta-
diene/styrene = 30~60/0~10/10~20/20~40%. Transparent ABS has been
produced by major ABS resin makers all over the world, including Toray,
Denka, BASF, Chimei, and LG Chem., and the compositions and manu-
facturing methods differ according to the makers. Although the names may
be differently designated, e.g., as transparent-(M)ABS, transparent HIPS,
transparent MBS, etc., depending on the characteristic features, they are
commonly called transparent ABS because there is no great difference in
the overall basic properties.
ABS resin has excellent physical properties including impact strength as
well as excellent processability. Transparent ABS is structurally similar to
such ABS resin and therefore maintains the balance between mechanical
properties and processability properties. Of course, although there is a small
change in properties by providing the transparency, it maintains the bal-
anced properties in comparison to other transparent resins.
Table 6.10 shows the general properties of transparent ABS. Since the
characteristics differ according to the makers and the grades, only the most
representative properties are listed. In addition, to show how the proper-
ties of the present transparent ABS are different from those of other trans-
parent resins, the properties of the different kinds of transparent resins
are also described.
One of the important properties in selection of the resins is the impact
strength. As can be shown from Table 6.10, poly(methyl methacrylate)
resin has excellent modulus and optical properties, but has the disad-
vantage that it may readily break due to a significantly low impact
strength. To compensate for such a disadvantage, impact-resistant
poly(methyl methacrylate) has been prepared using acrylate rubber.
However, its impact strength is still below 5.

TABLE 6.10 Properties of Transparent Resins
PMMA PMMA
ASTM Transparent (general- (impact
test Unit ABS purpose) resistance) PC
Izod impact D256 kg⋅cm/cm 15 1 4 > 30
Tensile strength D638 kg/cm 2 430 720 570 870
Tensile elongation D638 % 50 10 40 6
Flexural strength D790 kg/cm 2 670 1300 1100 1400
Flexural modulus D790 kg/cm 2 20,500 33,000 24,000 35,000
Processing temp. °C 210 200 220 300
Total transmittance D1003 % 90 93 91 89
Haze D1003 % 2.0 0.5 1.0 1.0