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Handbook of Size Exclusion Chromatography and Related ...

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high-molecular-weightmaterialaswellasthereduction<strong>and</strong>shifting<strong>of</strong>thepeakas<br />

the polymer degrades. The small response <strong>of</strong> the asphalt to the specific viscosity<br />

detectorresultsfromscalingtokeepthepolymerpeakonscale.TheRIresponseis<br />

typical<strong>of</strong>asphalts<strong>and</strong>muchmorenearlyrepresentstheactualamount<strong>of</strong>polymer<br />

present, but it is much less sensitive to the changes that occur. It also shows the<br />

usual growth with oxidation in the LMS peak near 24 minutes.<br />

When ground tire rubber is blended with asphalt at high temperature, some<br />

<strong>of</strong> the rubber degrades sufficiently to go into solution <strong>and</strong> this is clearly visible<br />

withSEC(66,91).Billiteretal.(92,149,150)usedSECwithaviscositydetectorto<br />

study the effect <strong>of</strong> mixing variables on rubber disassociation in asphalt <strong>and</strong> the<br />

effectonproperties.Figure18showstheeffect<strong>of</strong>highshearmixing<strong>of</strong>rubberinto<br />

asphalt. Initially apeak appears at about 200,000 MW by polystyrene st<strong>and</strong>ards,<br />

but with curing thepeak grows <strong>and</strong> then degrades. The size <strong>of</strong>the peak compared<br />

to the peak in Fig. 17 shows that arelatively small fraction <strong>of</strong> the rubber actually<br />

dissolves, but the degradation <strong>of</strong> this peak is a fair measure <strong>of</strong> the reduction in size<br />

<strong>of</strong> the remaining products.<br />

Figure 18 SEC analyses <strong>of</strong> a crumb-rubber modified resin at different stages <strong>of</strong> curing<br />

<strong>and</strong> its base asphalt (1000/500A ˚ , 30cm ultrastyragel, 50A ˚ , 60cm PLgel, THF at 1mL/min,<br />

100mL, 2wt% solution, IV detector).<br />

© 2004 by Marcel Dekker, Inc.

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