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Chap._400009 - monomers and the manner in which they are...

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In contrast to the emulsion process, the suspension process begins with polybutadiene rubber which is soluble in the styrene monomers. A typical recipe might be as follows: The first step is the dissolution of polybutadiene in styrene monomers to produce a homogeneous solution. A monomer soluble free-radical initiator is added to the solution along with acrylonitrile. It is then heated up to 80- 120 o C with shearing agitation for a period of 2-8 hour to reach 25-35% conversion. Phase inversion has taken place with SAN as the continuous phase. This polymer syrup is then transferred toa suspension reactor where it is dispered in water with agitation. The reactor is then heated up to 100-170 oC for 6-8 hour to complete the polymerization. * Properties and Applications As has already been mentioned, the range of possible ABS polymers is very large since both the ratio of the three
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Unformatted text preview: monomers and the manner in which they are assembled in the final product can be varied considerably. Thus commercial ABS polymers are available with appreciable differences in properties, but they are generally characterized by high impact strengths and softening points as high as, or higher than, straight polystyrene. In genenal, emulsion process is used to make materials of high impact strength, and bulk and suspension processes are preferred for the materials with less impact strength. The physical properties are the reflection of polymer morphology. The emusion process produce the ABS product containing solid rubber particles with the size about 0.1 um in diameter. On the other hand, the suspension (bulk) produce ABS with much larger overall rubber particle size, up to 1 mm in diameter, with the sub-enclosed SAN in the rubber domains....
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