Celcon properties

Grades of acetal resins specifically designed to enhance the excellent lubricity of the material, without sacrifice in other properties, are known. These include Delrin AF, Ultraform N2311, and Celcon LW materials. Antistatic grades, particularly useful in electronic appHcations, have been developed. At least one recendy introduced new grade, Celcon SR90, claims good scuff resistance. 

Property ASTM method Delrin 500 homopolymer resin Celcon M90 copolymer resin ... 

The electrical insulation properties of the acetal resins may be described as good but not particularly outstanding. There are available alternative materials which are better insulators and are also less expensive. There are, however, applications where impact toughness and rigidity are required in addition to good electrical insulation characteristics, and in these instances acetal resins would be considered. Table 19.3 lists some of the more important electrical characteristics of Delrin acetal resin. Data for the trioxane-based copolymer resin (e.g. Celcon) are virtually identical. 

Based on knowledge of relative properties and costs, it appeared to us that Celcon had some advantages to offer in the application. We quickly learned that people making tubing from nylon were extruding at rates up to 150 feet per minute. At the time, our company had very little experience with the extrusion properties of Celcon and we learned that under conditions which were being used... 

The potential volume involved and our assessment of the property benefit of Celcon in the application were sufficient to justify a lab program whose objective was to develop a polymer or modify the extrusion process so that Celcon would extrude at comparable or faster speeds than the material being used. After some nine months of effort an extrusion die was designed that permitted extrusion speeds of 450 feet per minute while making tubing with the tolerance specifications established by the customer. The foregoing is an example of a type of process development work described in the preceding paper. 

Polyoxymethylene (POM) is, again, a crystalline polymer, with a melting point of about 180 °C. Its mechanical properties enable it to gradually replace metals in a number of applications. Many technical parts are being made from POM, such as gear wheels, bars, automotive accessories, parts of several apparatuses and machines. The polymer is used as such (e.g. Delrin ), but also as a copolymer with a small amount of ethylene oxide (e.g. Celcon and Hostaform ). 

Acetal translucent crystalline polymer is one of the stiffest TPs available. It provides excellent hardness and heat resistance, even in the presence of solvents and alkalies. Its low moisture sensitivity and good electrical properties permit direct competition with die-cast metal in a variety of applications. In addition, acetal has extremely high creep resistance and low permeability. Acetal is also available as a copolymer (Hoechst Celanese Corp. s Celcon) for improved processability. The homopolymer (DuPont s Delrin) has a very low coefficient of friction and its resistance to abrasion is second only to nylon 6/6. Acetals are frequently blended with fibers such as glass or fluorocarbon to enhance stiffness and friction properties. Acetal is not particularly weather-resistant, but grades are available with UV stabilizers for improved outdoor performance. Acetal, whether homopolymer or copolymer, is not used to any significant degree in forming structural foams. 

CELCON Acetal Copolymer Properties, Brochure 10M, Celanese Corp., New York, June 1983. 

Features Thermoplastic engineering resin UV stabilized Properties Nat. color sp.gr. 1.41 dens. 1.41 g/cm water absorp. 0.22% tens. str. 8800 psi (yield) tens, elong. 75% impact str. (Izod) 1.5 ft-lh/in. notched hardness (Rockwell) M80 mold shrinkage 22 mils/in. (flow direction) heat deflection temp. 230 F 264 psi flamm. HB (UL94) Celcon M90UV [Ticona]... 

TABLE 8.4 Celcon Acetal Copolymer—Typical Properties... 

TABLE 2. Properties of Celcon acetal specialty products. 

Degradation of polyacetals may also occur by oxidative attack at random along the chain leading to chain scission and subsequent depolymerization (unzipping). Oxidative chain scission is reduced by the use of antioxidants (see Chapter 1 of Plastics Fundamentals, Properties, and Testing), hindered phenols being preferred. For example, 2,2 -methylene-bis(4-methyl-6-r-butylphenol) is used in Celcon (Celanese) and 4,4 -butylidene bis(3-methyl-6-f-butylphenol) in Delrin (Du Pont). 

Table 5.13 Tribological Properties of RTP Company ESD 800 Static Dissipative (Base Polymer POM-Co Celanese Celcon M90) Versus 1018 C Steel...

---