Polyacetals development

Sodium etch Sodium hydroxide Sanitizing melamine or urea polymer, polyolefin, polyethylene oxide, polystyrene, polysulfone, and styrene-acrylonitrile (SAN) Fluoroplastics and some polyesters Polystyrene, polyesters, polyamide, and polysulfone Homopolymer polyacetal Developed by... 

Sanitizing Homopolymer polyacetal Developed by DuPont, US patent 3,235,426... 

The combination of weak links and unzipping can be catastrophic and has been a particular problem in the commercial development of some polymers, in particular polyacetals. 

The intriguing structural complexity and often potent biological activity exhibited by many polyacetate-derived natural products have generated a continuing interest in the development of efficient, stereoselective approaches to the assembly of repeating l -diol subunits. One such method is the alkylation and reduc-... 

Poiyacids, based on anionicaiiy polymerized giyoxyiic esters were cleverly developed by Monsanto and the work published in a series of patents(49) and papers(50,51). The polymers are polyacetals, stable in alkali, but not in acid hence, in use as detergents, they are stable, but hydrolyze as the pH falls to 7 in the sewer systems, after use, to biodegradable monomer. 

Masamoto J, Matsuzaki K, Iwaisako T, Yoshida K, Kagawa K, Nagahara H (1993) Development of a new advanced process for manufacturing polyacetal resins. Part 3. End-capping during polymerization for manufacturing acetal homopolymer and copolymer. J Appl Polym Sci 50 1317-1329... 

Cationic polymerizations are not only important commercial processes, but, in some cases, are attractive laboratory techniques for preparing well-defined polymers and copolymers. Polyacetal, poly(tetramethyl-ene glycol), poly(e-caprolactam), polyaziridine, polysiloxanes, as well as butyl rubber, poly(N-vinyl carbazol), polyindenes, and poly(vinyl ether)s are synthesized commercially by cationic polymerizations. Some of these important polymers can only be prepared cationically. Living cationic polymerizations recently have been developed in which polymers with controlled molecular weights and narrow polydispersity can be prepared. 

Among the more than several uses for polyethers in ordn application is as a binder for extrusion-cast expls (Ref 3), and in a caseless proplht charge where the charge is used as an ammo element (Ref 5). Also, some development work on the use of Polyacetal resins (polyformaldehyde) as a fuel has been done by Singhal T ien y[Pg.816]

Tomlison R, Heller J, Duncan R, Brocchini S Pendent chain functionalised polyacetals that display pH-dependent degradation A platform for the development of novel polymer therapeutics, Macromolecules 2002, 35, 473 80. 

Regardless of the water content or AK level, no DGB s have yet been observed in any nylon specimens (either Series A or Series B). By contrast, the discontinuous growth of fatigue cracks has been described in studies of both crystalline and amorphous polymers [for example, in polyacetal (29,30), polyethylene ( ), and a variety of poorly crystalline or amorphous polymers ( ) ]. While the process of DGB formation in poorly crystalline or amorphous polymers is fairly well understood ( 5, 12,29,32) the role of well developed crystallinity is not clear. Hence the reason why DGB bands are not observed in nylon 66 is as yet unknown. 

In 1947, Du Pont began a development program on the polymerization and stabilization of formaldehyde and its polymer. Twelve years later, Du Pont brought the unzipping tendency under control with proprietary stabilizers and commercially announced Delrin polyacetal polymer (Figure 3). The key to the stabilization of poly formaldehyde resins appears to be a blocking of the terminal... 

INHAM-2 [130] has been developed on the base of PA and finely dispersed vulcanized rubber for operation in friction joints under the simultaneous effect of hostile and abrasive environments. The material contains polyacetal of the CFD or CTD series as a functional additive and an oil mixture with Cl as a lubricant. 

Plastics have been widely accepted in industrial equipment development as materials for many critical components and for accessories where such features as toughness, abrasion resistance, corrosion resistance, electrical insulation capability, nonstick properties, and transparency are of importance. For example, PVC, polyacetal, and PTFE are used for pipes, pumps, and valves because of their excellent corrosion resistance. Nylons are used for such diverse applications as mine conveyor belts and main drive gears for knitting machines and paper making equipment because of their excellent abrasion resistance, toughness, and low coefficient of friction. 

Several excellent reviews have recently been published that describe the broad field of degradable biomedical polymers [9,10]. Well-known hydrolytically degradable polymers developed or being developed for biomedical used include homo- and copolymers of polyamides (usually derived from amino adds), polyesters, polyanhydrides, poly(ortho ester)s, poly(anfido amines), and poly(P-amino esters). This chapter is focused on polyacetals, which... 

We also reported the fer-polymerization strategy with the intent to combine DES (diethylstilboestrol), which is a diol, into the polymer backbone [23]. Hydrolytic degradation studies with these bioresponsive polymers showed an enhanced rate of hydrolysis of the polymer backbone at pH 5.5, in which 65% of DES was released over 96h, in comparison to pH 7.4, where only 4% of DES was released during the same time [23]. This DES containing ter-polyacetal has continued to be developed by Vicent etal. [32,71]. 

More recently, camptothecin (CPT) was conjugated to poly(l-hydroxymethylethylene hydroxymethylformyl) (PHF or Eleximer ) and the conjugate 11 (XMT-1001) is currently in clinical development [72,73]. The polyacetal is derived from the exhaustive oxidation of dextran [74]. CPT is poorly soluble and prone to rapid inactivation through lactone ring hydrolysis in vivo [75]. As a cytotoxic compound, CPT has been used in many efforts to develop other CPT-polymer conjugates [45,76,77]. The sodium salt of CPT has also been examined in phase I trials, but only modest responses were observed while severe toxicities remain. 

While much recent work has been described to develop polyacetals for drug delivery applications, and historically they have been used as implant materials, more recently, they have been examined as potential scaffold materials in tissue engineering. Implants of Delrin (polyoxymethylene) to repair heart valves were examined, but there was too much swelling in vivo [127]. However, this polyacetal has been used as an orthopedic implant [128] and as an orthopedic implant-coating material [129,130] to interface with bone tissue as this polyacetal has a similar modulus to bone. Ultrasound is used in the diagnosis of osteoporosis and porous polyacetal blocks were found useful to gain insights into bone porosity and ultrasonic properties [131]. 

In order to obtain greater information about the composition of polymers and macromolecular material, modifications to the analytical pyrolysis process have been developed. These have included on-line pyrolysis hydrogenation of polyolefines using hydrogen carrier gas and a palladium catalyst. Polyacetals have been pyro-lyzed in the presence of a cobalt catalyst to produce cyclized compounds that afford greater information about the structure of the polymer. ... 

Acetal, (Polyacetal) Poly-oxymethylene (POM) Acetal is a polymer obtained through an addition reaction of formaldehyde — (CH2—0) . It excels in mechanical performance and is regarded as a prominent engineering polymer. It appeared in 1959 with the commercial name Delrin . A short time later a useful copolymer was also developed with a cyclic ether like ethylene oxide. The monomer formaldehyde is a gas produced mostly by oxidizing methanol, and it is very useful in thermoset polymers like phenol, urea and melamine-formaldehydes. For high purity it is initially converted to trioxane or paraformaldehyde. The polymerization is carried out by ionic mechanism, wherein the monomer is dispersed in an inert liquid (heptane). The molecular weights reach 20,000 to 110,000. 

Acetal polymers, also known as POM or polyacetal, are formaldehyde-based thermoplastics that have been commercially available since the 1960s. Polyformaldehyde is thermally unstable. It decomposes on heating to yield formaldehyde gas. Two methods of stabilizing polyformaldehyde for use as an engineering polymer were developed and introduced by DuPont, in 1959, and Celanese in 1962. 

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