Page 156 - Engineering Plastics Handbook

Acrylonitrile-Butadiene-Styrene (ABS) Resin 129

ASA resin
ASA resin is a terpolymer formed by graft polymerization of acrylonitrile
and styrene onto acryl rubber, and it is opaque. By adjusting the compo-
sition of acrylonitrile, acryl rubber, and styrene and the grafting ratio, a
resin having high impact strength and excellent fluidity in molding can
be prepared.
In comparison to ABS resin, ASA resin has somewhat greater specific
gravity, somewhat less tensile strength, and somewhat greater elonga-
tion. The other properties of ASA are comparable to those of ABS.
For weatherability it has been reported that after outdoor exposure
of ASA resin, there is extremely little deterioration of the mechanical
properties such as impact and elongation, and there is substantially no
change in appearance. ASA resin can endure the conditions of outdoor
use for a long time in comparison to the general-purpose resin.
In addition, ASAresin has excellent molding processability and is molded
under the same molding conditions as is ABS resin. Particularly, since the
fluidity of ASAresin is superior to that of a high rigid ABS resin, the large
product with small thickness is more easily processed with ASA resin
than with ABS resin. Further, since ASA resin has excellent elongation,
it is suitable for processing parts requiring deep design.
ASA resin has been sold as the flame-retardant grade and finer glass-
reinforced grade, which can be used in broad applications. ASA resin has
seen use in substantially the same application fields as ABS resin, and
particularly has been developed mainly for the outdoor product which
demands the weatherability:

1. Fields related to electricity: switch case, housing (washing machine,
refrigerator, ventilator, pump, room cooler, etc.), fluorescent lamp,
mercury lamp cover, antenna cover, door horn, metacover
2. Fields related to automobiles: headlight body, radiator grill, limp
body, parts of farming machines
3. Others: industrial articles, bolts, signal boards, parts of fire extinguishers

AES resin
AES resin has excellent heat resistance, impact resistance, and weather-
ability, as do other weatherable resins. For example, after standing at
88°C for 14 h, the strength of AES resin according to the Izod impacting
method is lowered only by 5 to 8%, whereas the strength of ABS resin is
greatly lowered by about 30 to 40%. In addition, under the same conditions
the falling weight impact strength of AES resin shows excellent mainte-
nance in comparison to ABS resin. Further, the capacity of AES resin
having oxidation resistance, yellowing resistance, etc., is sufficiently supe-
rior to that of ABS resin.