7-Polymer Cross-Linking and Viscosity

7-Polymer Cross-Linking and Viscosity - Results and...

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Results and Discussion The purpose of this experiment was to determine the effect of cross-linking on polymer solution viscosity. Borate ion, B(0H) 4 - was used to cross-link strands of poly(vinyl alcohol). 1. Prepare a cross-linked PVA solution. 2 g of PVA were slowly dissolved into water (approximately 90ºC) for 1.5 hours. When it was complete, the solution was clear. The borax was dissolved in water to form a solution. Na 2 B 4 O 7 . H 2 O 2 B(OH) 3 (aq) + 2 Na + (aq) + 2 B(0H) 4 - (aq) + 3 H 2 O(l) The borate ions were able to cross-link the PVA by forming hydrogen bonds. 2. Remove cross-linking by addition sulfuric acid. 2 B(0H) 4 - (aq) + H 2 SO 4 (aq) 2 B(OH) 3 (aq) + SO 2 - (aq) + 2 H 2 O(l) 2. Restore cross-linking by added a base to neutralize the acid. Therefore, cross-linking increased the polymer solution viscosity and there is an observable change. In addition, the removal of the cross-linking by sulfuric acid did not bring about a complete restoration of the pre-cross-linked polymer solution viscosity. The neutralization of the acid led to the restoration of cross-linking and an increase in
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7-Polymer Cross-Linking and Viscosity - Results and...

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