Page 153 - Engineering Plastics Handbook

126 Engineering Plastics

styrene-co-methyl methacrylate styrene-co-maleic anhydride, SMA-MMA,
phenyl maleimide, etc., with grafted ABS. See Table 6.13. Among these
AMS-based SAN is primarily used to produce heat-resistant ABS. The
method used for manufacturing AMS-based SAN is generally the emul-
sion polymerization method or the bulk polymerization method. The emul-
sion polymerization method can readily control styrene/acrylonitrile
content and molecular weight, but includes a large amount of the reaction
additives for polymerization, which may cause problems. SAN produced
by the bulk polymerization method has excellent producibility, but it is rel-
atively hard to control acrylonitrile and molecular weight in practice.
In the 1950s Borg-Warner, which first commercialized ABS, introduced
the product having well-balanced mechanical and heat resistance prop-
erties by developing the ABS final product utilizing α-methyl styrene-
co-acrylonitrile copolymer.
In the 1970s, different from the method for producing heat-resistant
ABS by generally applying AMS-based SAN, the method for improving
heat resistance properties and further providing excellent impact strength
by applying styrene-co-maleic anhydride was reported by DOW Chemical.
In the 1980s, in the method for improving heat resistance properties and
further providing melt flowability and surface properties, the AMS com-
ponent, instead of styrene, is grafted onto the grafted ABS, which is then
compounded with SAN. This is in contrast to the method for preparing
heat-resistant ABS product by applying heat-resistant SAN.
Further, Monsanto developed the technology to prepare heat-resistant
ABS having excellent mechanical properties and reinforced weatherabil-
ity by introducing the terpolymer of styrene–maleic anhydride–methyl
methacrylate into ABS to produce heat-resistant ABS, which has excellent
heat resistance properties.

TABLE 6.13 Composition of Heat-Resistant Matrix
Component

Copolymer of α-methyl H CH H H
3
syrene-acrylonitrile C C C C
H H C N n

H H H H H H
Terpolymer of PMI-
styrene-acrylonitrile C C C C C C
O C C O H H C N
N
n