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Anisotropic aspects of the environmental stress cracking of acrylonitrile‐butadiene‐styrene and styrene acrylonitrile copolymers in methanol
Author(s) -
Faulkner Douglas L.
Publication year - 1984
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760241506
Subject(s) - materials science , composite material , natural rubber , acrylonitrile , acrylonitrile butadiene styrene , cracking , anisotropy , melt flow index , styrene , stress (linguistics) , environmental stress cracking , copolymer , polymer , stress corrosion cracking , linguistics , philosophy , physics , alloy , quantum mechanics
Critical strains causing environmental stress cracking of injection‐molded poly(acrylonitrile‐butadiene‐styrene) (ABS) and poly(styrene‐acrylonitrile) (SAN) plaques were determined upon exposure to methanol. Measurements were obtained for samples strained either parallel or perpendicular to the melt flow direction and for samples located at various distances from the mold gate. Critical strains were significantly higher in the direction parallel to the melt flow compared to the transverse direction. The degree of anisotropy increased with increasing rubber content. For ABS containing 46 percent rubber, the critical strain at one point was determined to be 2.99 percent in the direction of melt flow, but only 0.47 percent in the orthogonal direction. For this material, critical strains determined parallel to the melt flow decreased with distance from the gate; whereas, critical strains for SAN and ABS containing 30 percent rubber remained essentially constant. Orientation of the plaques was assessed using shrinkage determinations and a thermal conductivity technique. Though a straightforward correlation of orientation with critical strain is observed for ABS, a similar relationship is not observed for SAN. These results suggest that although stress cracking occurs in the glassy matrix of ABS, it is the dispersed rubbery phase which controls the magnitude of strain required to initiate cracking.