Gelation number average molecular weight

The extension of blsmaleimlde photoaddltlon to polystyrene crossllnklng represents a practical application of photopoly-merlzatlon with potential in the area of light curable coatings. Initial crossllnklng experiments have been concerned with the effect of both aliphatic and aromatic blsmaleimldes on gelation times of polystyrene solutions. A commercial atactic polystyrene with number average molecular weight of 270,000 was used for this work. 

Table I. Number average molecular weight at gelation as a function of for R = 1.00...

The authors collected the test data shown in Table 9.10. From these data it can be noted that the number-average molecular weight, or Af , of a commercial emulsion SBR such as IISRP 1500 or 1712 is typically 90,000-175,000. The primary molecular weight of a solution-polymerized polymer produced with an anionic lithium catalyst can, in contrast, be increased toward 250,000 without gelation. In addition, emulsion-polymerized SBR contains only about 92% rubber hydrocarbon as a result of the presence of residues from the production process solution polymers tend to be near 100% hydrocarbon. As a consequence, the authors concluded that the number-average molecular weight... 

Fig. 3.8 Number-, weight-, and z-average molecular weights as functions of the reactivity in the gelation reaction of polyfunctional molecules R Ay. ...

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