Page 144 - Engineering Plastics Handbook

Acrylonitrile-Butadiene-Styrene (ABS) Resin 117

High MW

Stress

Strain
Figure 6.6 Hot tensile profile according to molecular weight
(150°C, 15-min annealing).

For a refrigerator inner door cabinet, the most widely used product among
extrusion ABS resins, cracks may occur due to chemical attack by the foam-
ing agent (cyclopentane, HCFC-141b, HFC-245fa, etc.) of polyurethane
foam used as the insulation material after a vacuum thermoforming
process. The ABS demands a superior chemical resistance property.
The polyurethane foaming agents used in a refrigerator are shown in
Table 6.8.
Chemical cracking due to the refrigerator foaming agent can be pre-
vented by controlling the rubber content, acrylonitrile content, and
molecular weight of styrene-acrylonitrile copolymer, or adding a chemi-
cal resistance modifier to provide better chemical resistance to ABS resin.

Stress (a) (b)

Strain
Figure 6.7 Hot tensile profiles (150°C) for extrusion ABS: (a)
without high-MW additives; (b) with high-MW extrusion ABS.