Polyoxy methylene

An alternative approach to the production of thermally stable polyoxy-methylenes was made by chemists of the Celanese Corporation of America and the commercial products were marketed as Celcon. Hostaform and Duracon. The principle of thermal stability in this case is the copolymerisation of formaldehyde with a second monomer which is a cyclic ether of the general form shown in Figure 19.3 (I). 

Zavitsas et al. added terms for the extent of hemiformal and paraformaldehyde formation. Hemiformal formation slows the methylolation reaction as does the presence of paraformaldehyde. They report that only monomeric methylene glycol appears to methylolate. They point out that the terms for the two polyoxy-methylene species partially cancel one another, as depolymerization of paraformaldehyde naturally occurs while hemiformal formation is increasing due to methylolation. They observe that hemiformals form only on the methylolphenol hydroxyls and not on the aromatic hydroxyl. They calculate that the average number of methoxy groups involved in each of the hemiformals is about two in addition to the original methylol. There is no selectivity for ortho versus para positions in hemiformal formation. 

Polyacetals. Simionescu and coworkers (28) have extended to polyoxy-methylene the process of grafting vinyl polymers (acrylonitrile and methylmethacrylate). They performed the synthesis using a virbomill at room temperature under vacuum (10.1 Torr). The initial monomer-polymer ratio was 1 -5/1.0 and the degree of vibromill packing 0.44. Before milling the polyoxymethylene granules were dissolved in dimethyl formamide and repredpitated with the aim of stabilizer removal and for reduction of polymer particle size (from 2-2.5 mm to 0.05-0.10 mm). Full details of the reaction have been described (40). 

Polymer Poly- ethylene Polyoxy- methylene Polytetra- fluoro- ethylene Natural Rubber Gutta Percha... 

During the initial polymerization of trioxane with (C4H9)2OBF3 in melt or solution, no solid polymer is formed, and the reaction medium remains clear. Using a high resolution NMR spectroscope, C. S. H. Chen and A. Di Edwardo observed the appearance of soluble linear polyoxy-methylene chains. In the cationic copolymerization of trioxane with 1,3-dioxolane, V. Jaacks found also that a soluble copolymer forms first and turns later into a crystalline copolymer of different composition. Crystallization and polymerization proceed simultaneously in the solid phase. 

To investigate the copolymerization of trioxane with dioxolane and to determine r1 by the excess method, a molar ratio of trioxane to dioxolane of 100 1.8 was used. All polymerizations were run in methylene dichloride at 30°C. with SnCl as initiator. To reduce the influence of formaldehyde production at the beginning of copolymerization, dioxolane was added to the solution of trioxane and initiator only at the end of the induction period—i.e., at the appearance of the first insoluble polyoxy-methylene. After various reaction times polymerizations were terminated by adding tributylamine. Monomer conversions were determined by gas chromatography, the liquid phase being injected directly. When conversions were small, isolation and analysis of the copolymer yielded more accurate results. 

For the preparation of methylene acetals, which are intrinsically much more stable ring-systems, higher temperatures, even in the presence of acids, are more common. The condensation of aldoses with polyoxy-methylene was carried out by fusing the reactants together in the presence of sulfuric acid. A more recent procedure for the preparation of di-0-methylene-D-glucose (as its 6-acetate) employs paraformaldehyde, glacial acetic acid, and sulfuric acid at 100° for 1 hour. ... 

AI3-01363 Aldeform CCRIS 4732 EINECS 203-812-5 Formagene Formaldehyde, trimer HSDB 3416 Marvosan Metaformaldehyde NSC 26347 Para-formaldehyde Polymerized formaldehyde Polyoxy-methylene Triformol Triossimetilene 1,3,5-Trioxa-cyclohexane Trioxan 1,3,5-Trioxan Trioxane s-Tri-oxane ... 

Dynamic mechanical and NMR investigations of crystals grown from dilute solutions for polymers other than linear polyethylene have been much less extensive. Studies have been reported for the linear polymers polyoxy methylene (3, 40, 94), poly (ethylene oxide) (3, 78), and nylon 6 (42), and the branched polymers polypropylene (40), poly-l-butene (19, 95), poly(4-methyl-l-pentene) (33), poly (vinyl alcohol) (78), and branched polyethylene (78). In addition, dielectric loss measurements have been made on crystal aggregates of poly (ethylene oxide) (23), poly (vinyl alcohol) (68), and polyoxymethylene (3) and mechanical loss measurements have been carried out on polyoxymethylene formed by solid state polymerization (94). 

Figure 3.8 Crystal structure of polyoxy methylene. (a) Skeletal model open circle, oxygen atom solid circle, methylene group, (b) Electron density map on a cylindrical section of radius 0.691 A, which is cut open flat for presentation purpose. (From Uchida and Tadokoro.25)...

TPU/POM Blends Thermoplastic polyurethane, TPU, and polyoxy-methylene, POM were mixed in the desired ratios using a 30-mm single-screw extrader (L/D = 20) with a mixing head, at 170-200°C (Table 11.9). 

Formaldehyde Polyoxy- methylene Hexane Anionic type Atm -60 to 160 Precipitates as formed... 

Polyoxy- methylene POM -CH2-O- Celcon, Delrin, lupital, Tenac, Ultraform... 

Despite numerous studies, the observation of LAM in other polymers proved elusive for quite some time (105,106). For isotactic polypropylene, LAM was not obtained imtil 25 years after the initial observation. The first LAM observation was for an isotactic polypropylene prepared under special conditions of extrusion and orientation (107). Both sample transparency and the preferential reduction in Rayleigh scattering made the observation possible (Fig. 10). LAM has now been observed in a number of polymer systems such as PTFE, polyoxy methylene, PEO,... 

In the above examples the polymerisation takes place by the opening of a carbon-carbon double bond. It is so possible to open carbonyl carbon-oxygen double bonds and nitrile carbon—nitrogen triple bonds. An example of the former is the polymerisation of formaldehyde to give polyformaldehyde (also known as polyoxy methylene and polyacetal) (Figure 23). 

Figure 1 Polymer interpretation chart. PAI, polyamideimide PC, polycarbonate UP, unsaturated polyester PDAP, diarylate phtalate resin VC-VAc, vinyl chloride-vinyl acetate copolymer PVAc, polyvinyl acetate PVFM, polyvinyl formal PUR, polyurethane PA, polyamide PMA, methacrylate ester polymer EVA, ethylene-vinyl acetate copolymer PF, phenol resin EP, epoxide resin PS, polystyrene ABS, acrylonitrile-butadiene-styrene copolymer PPO, polyphenylene oxide P-SULFONE, poly-sulfone PA, polyamide UF, urea resin CN, nitrocellulose PVA, polyvinyl acetate MC, methyl cellulose MF, melamine resin PAN, polyacrylonitrile PVC, polyvinyl chloride PVF, polyvinyl fluoride CR, polychloroprene CHR, polyepichlorohydrin SI, polymethylsiloxane POM, polyoxy-methylene PTFE, polytetrafluoroethylene MOD-PP, modified PP EPT, ethylene-propylene terpolymer EPR, ethylene-propylene rubber PI, polyisoprene BR, butyl rubber PMP, poly(4-methyl pentene-1) PE, poly(ethylene) PB, poly(butene-l). (Adapted from Ref. 22, p. 50.)...

Figure 12.32 Plot of brittle stress at about — 180 °C against a line joining yield-stress values at —20 °C (o), respectively, for various polymers. Line A divides polymers that are brittle unnotched from those that are ductile unnotched but brittle notched, and line B divides polymers that are brittle notched but ductile unnotched from those that are ductile even when notched. PMMA, poly(methyl methacrylate) PVC, poly(vinyl chloride) PS, polystyrene PET, poly(ethylene terephthalate) SAN, copolymer of styrene and acrylonitrile CA, cellulose acetate PP, polypropylene N, nylon 6 6 LDPE, low-density polyethylene POM, polyoxy-methylene PB, polybutene-1 PC, polycarbonate PTFE, polytetrafluoroethylene. (Reproduced with permission from Vincent, Plastics, 29, 79 (1964))...

Conductive multiphase composites have been obtained by dilution of polyoxy-methylene/carbon black in the polyethylene-based phase (Lipatov et al. 1983). In this manner, the filler is localized at the interface between the polymeric components. Though a reinforcement agent was excluded to the interface of the polyoxymeth-ylene phase as it crystallized, a small percent remained dispersed in the component The conductive network at the polyethylene/polyoxymethylene interface enhanced the conductivity level at lower filler amounts. 

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