Determining the molecular weight distribution of elastomers (both natural and synthetic) is a very important analytical technique used to correlate with physical properties. Elastomer formulations may be very complicated, with blends of polymers being used, as well as antioxidants, plasticizers, vulcanizers, accelerators, and a variety of fillers (carbon black, titanium dioxide, silica, etc.). The entire formulation may consist of only 50% (or even less) of the elastomer. These formulations are used extensively in the automotive and aerospace industries for everything from tires to O-ring seals. As is always the case in GPC analysis, the first thing we must do is calibrate our system, so here we show athird-order calibration curve using polybutadiene narrow standards as the calibrants.
There are also polyisoprene narrow standards available. Once again, two HR 5E's and a single HR2 were used for the column bank, maintained at 75 °C. In the case of elastomers, toluene is usually the solvent choice. THF may be used in many cases, but toluene tends to do a better job at dissolving some elastomers such as natural rubber, (cis - 1,4 polyisoprene). The dRI detector was used with the Alliance system. We chose polybutadiene narrow standards as they are similar in structure to most of the elastomers we looked at. Note the outstanding reproducibility for the applications that show the multiple distribution overlays.
Below are a few additional elastomer applications of interest:
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