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Paraformaldehyde (PFA) is the smallest polyoxymethylene, the polymerization product of formaldehyde with a typical degree of polymerization of 8–100 units. Paraformaldehyde commonly has a slight odor of formaldehyde due to decomposition.
In this procedure, a small amount of paraformaldehyde as a fine powder is added to the titrand before the titration. At the endpoint, the first excess of hydroxyl ions catalyzes the depolymerization of paraformaldehyde. The reaction is strongly endothermic and yields a sharp inflection. The titration plot is illustrated in Figure 13.
Depolymerization is also related to production of chemicals and fuels from biomass. In this case, reagents are typically required. A simple case is the hydrolysis of celluloses to glucose by the action of water. Generally this process requires an acid catalyst: H(C 6 H 10 O 5) n OH + (n - 1) H 2 O → n C 6 H 12 O 6
Depolymerizable polymers or Low-Ceiling Temperature Polymers refer to polymeric materials that can undergo depolymerization to revert the materials to their monomers at relatively low temperatures, such as room temperature. For example, the ceiling temperature T c for formaldehyde is 119 °C, and that for acetaldehyde is -39 °C. [1] [2]
At the ceiling temperature, the enthalpy term and the entropy term are equal, so that the rates of polymerization and depolymerization become equal and the net polymerization rate becomes zero. [1] Above the ceiling temperature, the rate of depolymerization is greater than the rate of polymerization, which inhibits the formation of the given ...
Thermal depolymerization (TDP) is the process of converting a polymer into a monomer or a mixture of monomers, [1] by predominantly thermal means. It may be catalyzed or un-catalyzed and is distinct from other forms of depolymerization which may rely on the use of chemicals or biological action.
Formaldehyde is less expensive and has a much longer shelf-life if some methanol is added to inhibit polymerization of the chemical to paraformaldehyde, but is much more volatile. Formaldehyde is also used as a gaseous sterilizing agent; in this case, it is prepared on-site by depolymerization of solid paraformaldehyde.
Significant progress in the choice of resist material was made in 2010 at IBM Research in Zurich, leading to high resolution and precise 3D-relief patterning [12] with the use of the self-amplified depolymerization polymer polyphthalaldehyde (PPA) [12] [13] and molecular glasses [14] as resist, where the polymer decomposes into volatile ...