Lab #8 - Polymers

Lab #8 - Polymers - Results and Discussion Poly(vinyl...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Results and Discussion: Poly (vinyl alcohol) or PVA is made by first polymerizing vinyl acetate then, the poly (vinyl acetate) is hydrolyzed in a basic solution which yields the acetate ion CH 3 CO 2 - and PVA. There are many –OH groups in PVA which causes it to form good hydrogen bonds, making PVA very soluble in water. It can also form good hydrogen bonds with other substances such as the borate ion, B(OH) 4 - . When B(OH) 4 - is added to an aqueous PVA solution , the ion cross links the PVA by forming hydrogen bonds. This creates a three dimensional network of polymer strands that are hydrogen-bonded to the borate ions and water molecules. This cross-linking can be removed by the addition of an acid and restored by the addition of a base. This experiment tested the effect cross- linking had on the viscosity, or the resistance of a liquid to flow, of the polymer solution. Part A - Cross-linking PVA First, the PVA solution was made by adding 2.045g PVA to 90°C tap water. The PVA was added very slowly with constant stirring. A clear gel-like solution was formed. The viscosity was tested here before any cross-linking occurred. A ball bearing was used to test the viscosity of the PVA solution. It was dropped in the solution and the time it took to fall was measured. The ball took ~0.1 second to fall through 1.4cm of solution;
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This lab report was uploaded on 09/26/2007 for the course CHEM 2070 taught by Professor Chirik,p during the Fall '05 term at Cornell.

Page1 / 5

Lab #8 - Polymers - Results and Discussion Poly(vinyl...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online