Page 129 - Engineering Plastics Handbook

Acrylonitrile-Butadiene-Styrene (ABS) Resin 103

dimensional stability, and an increase in creep resistance, whereas the
broad MWD improves the flow properties and mold filling but also
increases the heat and pressure sensitivity of the melt. The increase in the
compositional ratio of the elastomer causes an increase in melt viscosity,
heat deformation resistance, and aging resistance and a decrease in stiff-
ness, as well as an increase in impact strength. Such a multiphase system
is affected by the interface condition between the rubber and thermo-
plastic matrix.
The final ABS resins completed by compounding grafted ABS and SAN
copolymer have been prepared by subdividing into general-purpose ABS,
flame-retardant ABS, extrusion ABS, heat-resistant ABS, transparent
ABS, weatherable ABS, etc., depending on the raw materials and additives
as applied.
Recently, the application of such ABS resins has been extended to one
engineering plastic formed through constitution of the composite alloy
with other resins, for example, ABS/PVC, ABS/polycarbonate, ABS/PA,
ABS/poly(methyl methacrylate), etc. The representative plastic compa-
nies producing such various kinds of ABS resins and ABS alloy products
include GE Plastic and Dow Chemical in the United States, Lanxess and
BASF in Germany, Chimei in Taiwan, LG Chem. in Korea, etc.
In this present chapter, we review the process for preparing ABS
resins, the final products, the main uses, etc., to help promote under-
standing about general ABS resins.

ABS Polymerization Process
ABS comprises the dispersed phase of styrene/acrylonitrile copolymer
grafted on polybutadiene rubber and the continuous phase of styrene/acry-
lonitrile copolymer. The use of SAN grafted on polybutadiene rubber pro-
vides high impact strength, processability, chemical resistance, staining
property, etc., as the characteristics peculiar to ABS resins.
The properties of ABS resins can be controlled by changing the compo-
sition and molecular weight of SAN, the particle size and size distribution
of polybutadiene rubber, the grafted ratio, etc. In using ABS resins, the
products having various properties can be manufactured by altering the
basic structure and the composition. Specifically it is possible to manu-
facture the products having various uses, including heat-resistant prod-
ucts, transparent products, and flame-retardant products.
The basic property of ABS resins is impact resistance. In connection with
this, various theories relating to the impact property have been estab-
lished. The rubber particles disperse impact energy through efficient gen-
eration and annihilation of craze. By such crazing, the energy is annihilated
with deformation of rubber particles to create the cavitation of rubber par-
ticles. This phenomenon can be confirmed through transmission electron