Polymer Cross Linking and Viscosity Conclusion

Polymer Cross Linking and Viscosity Conclusion - 2 SO 4 and...

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Conclusion By qualitatively observing the resistance of the PVA mixtures to the dipping of a wooden popsicle stick, the viscosities of the mixtures were inferred. Adding borax solution to the original PVA solution resulted in an increase in viscosity. Dissolving borax in water forms a solution of borate ions, and borate ions are known to cross-link PVA chains through formation of hydrogen bonds. It can thus be concluded that cross-linking increases viscosity. Adding H 2 SO 4 to this mixture resulted in a decrease in viscosity. H 2 SO 4 , an acid, is known to react with borate ions and remove cross-linking in PVA. It can thus be said that removal of cross-linking decreases viscosity. Adding NaOH to this mixture resulted in an increase in viscosity. NaOH is a base and is known to neutralize the acid H
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Unformatted text preview: 2 SO 4 , and consequentially restores cross-linking in PVA. This provides further evidence that an increase in viscosity occurs when there is cross-linking. The fact that the PVA mixture formed immediately after the addition of H 2 SO 4 was slightly more viscous than the original PVA mixture suggests that the H 2 SO 4 did not completely remove cross-linking that was formed by the borate ion solution. Also, the fact that the PVA mixture formed immediately after the addition of NaOH was slightly less viscous than the PVA mixture formed immediately after the borate ion solution was added suggests that the NaOH did not restore cross-linking to the extent of cross-linking induced by the borate ion solution....
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This note was uploaded on 01/31/2009 for the course CHEM 2070 taught by Professor Chirik,p during the Fall '05 term at Cornell.

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