Modification of recovered biocomponents Lab #3 Instruction Topic: Phisical modification of polymers Location: Date Compiled: Revision: Author(s): Email Address(es): Faculty: Department: Building, classroom / lab nr A-2/110 30 November2023 1 JW joanna.wolska@pwr.edu.pl Faculty of Chemistry K-25 Modification of recovered bio-components 1. Introduction Poly(vinyl alcohol) (PVAL) belongs to a small group of polymers that are not obtained by polymerization of its monomer, because vinyl alcohol is an unstable compound that rearranges to acetaldehyde. Poly(vinyl alcohol) is obtained indirectly by hydrolysis of poly(vinyl acetate) (PVA). The main feature that distinguishes PVAL from most polymers is its solubility in water, from which it can be precipitated using lower alcohols. PVAL also dissolves in higher alcohols, but it does not dissolve in organic solvents. PVAL is a thermoplastic and is a construction material with very high mechanical strength. Its typical applications are: oil- and gasoline-resistant foils and cables, fiber-forming material, ingredient of adhesives and varnishes, in the pharmaceutical industry as a cream thickener. The cross-linking reaction of PVAL with aqueous solutions of sodium silicate or sodium borate results in polymers whose properties depend on the amount of silicates or borates used. Small amounts of cross-linking agents, i.e. small amounts of silicate or borate ions capable of connecting polyalcohol molecules, produce a weak but quite flexible polymer that can be stretched into thin, almost transparent films. Using more of these ions leads to a polymer that is less flexible but can be formed into various shapes. 2. Objectives The aim of the exercise is to examine the effect of adding various amounts of sodium borate and water glass on the properties of polyvinyl alcohol. 3. Materials and Methods 3.1. Materials Poly(vinyl alcohol) Sodium borate Sodium silicate 3.2. Experimental procedure Dissolve poly(vinyl alcohol) in water to obtain 150 mL of a 4 wt.% solution. Then pour 25 mL of the solution into 6 beakers. Individually, add appropriate amounts of 4% borax (beaker #1 – 5 mL, beaker #2- 10 mL) or sodium silicate solution to each beaker (#3-10 mL, #4- 25 mL, #5- 35 mL, #6- 50 mL). After each addition of the reagent, the contents of the beaker should be mixed intensively using a glass stick. The polymer forms almost instantly and can be drawn out of the beaker using a glass stick. In the case of samples #4-#6 squeeze out excess liquid carefully (ATTENTION! wear gloves, the silicate solution is an irritant). Divide each of the six samples into two parts, then close one of them tightly in the described bag, and leave the other on the described laboratory slide (on the described foil) until the next classes. Estimate the elasticity of individual samples immediately after the reaction, after 30 - 45 minutes, and note changes after a week. 4. Reporting The report should compare the properties of the resulting systems as a function of the degree of cross-linking and the type of the cross-linking agent used. Explain what may be the reason for differences in the appearance and properties of individual samples. It is also necessary to provide information about the cross-linking reaction of poly(vinyl alcohol) with both cross-linking agents used in the laboratory and the reason for the different behavior of polymers stored in air and in welded bags. Literature [1] https://www.sciencedirect.com/science/article/abs/pii/S0032386110008311 Modification of recovered bio-components [2] https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6466192 Modification of recovered bio-components
