Paraformaldehyde — Polyoxymethylene

Palladium acetate, 61, 82 Paracyclophanes, table, 60, 47 Paraformaldehyde [30525-89-4], 61, 65 Paraformaldehyde (polyoxymethylene), 60, 88 Pentadecanoic acid, 60, 13 PENTAN01C-2-13C ACID, 3-HYDROXY-3-METHYL-5-(PHENYLMETHOXY)-[57830-65-6], 60, 94... 

Paraformaldehyde. Polyoxymethylene Paraform Formagene. Also erroneously referred to as Triformol or as rioxymethy . Polymerized formaldehyde, (CH2O)0. Obtained by concentrating formaldehyde soln. Use in mummifying dental pulp I. Curson. Brit. Dent. J. 121, 519 (1966) P. Hobenn, ibid. 129, 275 (1970). 

Paraformaldehyde [30525-89-4] is a mixture of polyoxymethylene glycols, H0(CH20) H, with n from 8 to as much as 100. It is commercially available as a powder (95%) and as flake (91%). The remainder is a mixture of water and methanol. Paraformaldehyde is an unstable polymer that easily regenerates formaldehyde in solution. Under alkaline conditions, the chains depolymerize from the ends, whereas in acid solution the chains are randomly cleaved (17). Paraformaldehyde is often used when the presence of a large amount of water should be avoided as in the preparation of alkylated amino resins for coatings. Formaldehyde may also exist in the form of the cycHc trimer trioxane [110-88-3]. This is a fairly stable compound that does not easily release formaldehyde, hence it is not used as a source of formaldehyde for making amino resins. 

In a classic paper titled "Uber Polymerisation" (45) he summarized his findings, and proposed formulas for polystyrene and polyoxymethylene (paraformaldehyde) that were linear, long chains. 

Polyoxymethylene is prepared by the polymerization of anhydrous formaldehyde (see Example 3-22) or of 1,3,5-trioxane (see Example 3-24) paraformaldehyde, obtained by polycondensation of formaldehyde hydrate, cannot be acetylated in hetero-... 

A reaction closely related to acetal formation is the polymerization of aldehydes. Both linear and cyclic polymers are obtained. For example, methanal in water solution polymerizes to a solid long-chain polymer called paraformaldehyde or polyoxymethylene ... 

Long-chain methanal polymers have become very important as plastics in recent years. The low cost of paraformaldehyde is highly favorable in this connection, but the instability of the material to elevated temperatures and dilute acids precludes its use in plastics. However, the end-capping of polyoxymethylene chains through formation of esters or acetals produces a remarkable increase in stability, and such modified polymers have excellent properties as plastics. Delrin (DuPont) is a stabilized methanal polymer with exceptional strength and ease of molding. 

The polymer F of formaldehyde is called polyoxymethylene or paraformaldehyde. It contains two OH groups, one at each end of the molecule, but these are omitted for clarity in the structural formula shown in Figure 7.14. This shows that one molecule of water, which is present everywhere even in the most careful work, has been incorporated. If these terminal OH groups are functionalized, paraformaldehyde can be used as plastic. When paraformaldehyde is heated with acid, it is transformed (entropy gain) into the cyclic trimer B from Figure 7.14, which is called 1,3,5-trioxane. 

Trioxane is not a good source of formaldehyde as it is very stable but the two other solids are good sources. Both paraformaldehyde and, more obviously, polyoxymethylene are polymers. Each molecule of either polymer consists of a large number of formaldehyde molecules reacted together. 

Paraformaldehyde is sometimes sold commercially under the label polyoxymethylene, and commercial polyoxymethylene (Prolabo—France) was used. 

Polyacetals form a different subclass of compounds with oxygen in the backbone chain. In this group are included polymers that contain the group -0-C(R2)-0- and can be formed from the polymerization of aldehydes or ketones. A typical example of a polymer from this class is paraformaldehyde or polyformaldehyde or polyoxymethylene (CH20)n. Polyoxymethylene can be prepared by anionic catalysis from formaldehyde in an inert solvent. Acetylation of the -OH end groups of the polymeric chain is common since it improves the thermal stability of the polymer. Some results reported in literature regarding thermal decomposition of these polymers are indicated in Table 9.2.1 [1]. 

Concentrated solutions containing formaldehyde are unstable, both oxidizing slowly to form formic acid and polymerizing (Gerberich et al. 1980). In the presence of air and moisture, polymerization takes place readily in concentrated solutions at room temperature to form paraformaldehyde, a solid mixture of linear polyoxymethylene glycols containing 90-99% formaldehyde (EPA 1984). 

When formaldehyde is heated with concentrated sulphuric acid, it forms the polymer polyoxymethylene, which contains at least 100 monomers. Polyoxymethylene is linear like paraformaldehyde. The main difference between the two of them is the number of monomers in the polymer. When heated, it also decays into formaldehyde. It is widely used in the textile industry. 

Fig. 19. Rates of radical production (excluding formyl radical) in polyoxymethylene materials on photolysis by 2537 A light at —196° C 1 copolymer, homopolymer, and paraformaldehyde photolyzed in vacuo 2 homopolymer and paraformaldehyde photolyzed under 10mm oxygen 3 copolymer photolyzed under 10mm oxygen, showing the great decrease In the number of radicals when the oxygen is depleted 4 copolymer photolyzed under 100 mm oxygen. [J. Polymer Sri. A-l, 7,1861 (1969),...

Cyclic acetals of ketoses are prepared most commonly from acetone or benzaldehyde formaldehyde, acetaldehyde, butanone, and cyclohexanone have been used occasionally. These carbonyl reagents are frequently used directly, although such derivatives as 2,2-di-methoxy- or 2,2-diethoxy -propane (acetone dialkyl acetals), or l,l-dimethoxyethane (acetaldehyde diethyl acetal), are often employed in experiments in which intermediate acetals are of interest,or in which the presence of water in the reaction mixture adversely affects the yield of products. A polymeric form of an aldehyde is the reagent to be preferred whenever the monomer is volatile for example, acetaldehyde is often used in the form of a trimer, paraldehyde, and formaldehyde is employed as formalin solution, as paraformaldehyde, or as polyoxymethylene. An excess of the carbonyl reagent is generally used as the solvent, and the condensation is usually effected at room temperature. 

Synonyms Eormaldehyde copolymer with urea Eormaldehyde/urea condensate Eormaldehyde/urea copolymer Eormaldehyde/urea polymer Eormaldehyde/urea precondensate Eormaldehyde/urea prepolymer Eormaldehyde/urea resin Formalin/urea copolymer Methylolurea resin Paraformaldehyde/urea polymer Paraformaldehyde/urea resin Polynoxylin Polyoxymethylene urea (INCI) UF Ure ormaldehyde adduct Urea/formaldehyde condensate Urea/formaldehyde copolymer Urea/formaldehyde oligomer Urea/formaldehyde polymer Urea/ formaldehyde precondensate Urea/formaldehyde prepolymer Urea, polymer with formaldehyde Classification Amino resin thermosetting resin Definition Thermosetting resin formed from condensation reaction of formaldehyde with urea formu/a (CH,N20 CH2O),... 

Polyoxyl 40 hydrogenated castor oil. See PEG-40 hydrogenated castor oil Polyoxyl 75 lanolin. See PEG-75 lanolin Polyoxyl oleyl ether. See Oleth Polyoxyl 10 oleyl ether. See Oleth-10 Polyoxyl 2 stearate. See PEG-2 stearate Polyoxyl 8 stearate. See PEG-8 stearate Polyoxyl 20 stearate. See PEG-20 stearate Polyoxyl 40 stearate. See PEG-40 stearate Polyoxyl 50 stearate. See PEG-50 stearate Polyoxyl 55 stearate. See PEG-55 stearate Polyoxymethylene. SeeTrioxane Paraformaldehyde... 

More studies on RCS are currently in progress and one in particular is aimed at determining if paraformaldehyde can be used as a more effective sterilant than Celcon polyoxymethylene, preferably also in the presence of an inert dispersant. Successful use of nonabsorbable tissue adhesives... 

Staudinger was convinced of the fallacy of the general notion that polymeric substances had to be association compotmds held together by partial valences. At the outset of his quest he was mainly interested in caoutchouc, polystyrene ( metastyrene ), and polyoxymethylene (paraformaldehyde). He first stated his... 

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