Acetal Homopolymer DELRIN

Acetal Homopolymer (DELRIN ) Adhesives recommended for this material include (6)  

Adhesives used to bond acetal homopolymer to itself and to other materials, such as aluminum, steel, natural rubber, neoprene rubber, and Buna rubber, include polyester with isocyanate curing agent, rubber-based adhesives, phenolics, epoxies, modified epoxies, and vinyls. Solvent cementing 

Bodied solvent cements are usually used to bond ABS. Adhesives recommended include epoxies, urethanes, second-generation acrylics, vinyls, nitrile-phenolics, and cyanoacrylates.  

These plastics [cellulose acetate, cellulose acetate butyrate (CAB), cellulose nitrate, cellulose propionate, and ethyl cellulose] are ordinarily solvent cemented, but for bonding to nonsolvent-cementable materials, conventional adhesives must be used. Adhesives commonly used are polyurethanes, epoxies, and cyanoacrylates. CeUulosic plastics may contain plasticizers that are not compatible with the adhesive selected. The extent of plasticizer migration should be determined before an adhesive is selected. Recommendations for conventional adhesives concerning specific ceUulosic types are as follows  

---

Acetal Homopolymer (DELRIN ) In general, solvent cements are relatively ineffective with DELRIN , a highly crystalline polymer. Methylene chloride, methylene chloride mixed with ethylene chloride, and DELRIN in methylene chloride have been used, however (6). 

The most common types of acetal polymers are the acetal homopolymer (Delrin by Du Pont) and the acetal copolymer (Celcon by Hoescht Celanese-Ticona). The homopolymer is produced from polyformaldehyde and the copolymer from trioxane (a crystalline form of formaldehyde). 

Acetal homopolymer (Delrin ) is a highly crystalline polymer (Du Pont Company, www2.dupont. com) that has excellent solvent resistance. The chemical structure and solvent resistance of homopolymer acetal lead to a relatively poor adhesion of solvent-based paints and cements. This is largely... 

Figure 19.8. Effect of humidity, time and temperature on the water absorption of acetal homopolymer resin (Delrin). (Du Pont Trade Literature).

Figure 19.9. Effect of absorbed water on the dimensions of acetal homopolymer resins ( Delrin ). (Du...

Because of the high solvent resistance of acetal homopolymers (e.g., Delrin ), molded surfaces cannot be joined by the use of cements unless they have been specially roughened. ... 

Tables 3.1—3.5 describe the compositions and designed purpose for the DuPont Delrin acetal homopolymers resins discussed in the rest of this section. The data for acetal homopolymer are found in Tables 3.6—3.15 and Figures 3.2—3.24.

Delrin is an acetal homopolymer whereas, Ultraform is a linear chained random copolymer of trioxane and another monomer made from trioxane the trimer of Formaldehyde... 

Delrin ST, Tough acetal homopolymer, DuPont Engineering Polymers... 

Delrin acetal homopolymer, copolymer Formosacon acetal copolymer... 

By the end of the decade, Delrin acetal homopolymer was recognized worldwide as an engineering plastic material. Primary markets were automotive, appliance, consumer products, hardware, industrial, electric, plumbing and stock shapes (18). 

Darvan Dispersing agents, Vanderbilt Dechlorane Plus Fire-retardant additive. Occidental D.E.H. Epoxy catalyst resins, Dow Delrin Acetal resin, DuPont Delrin ST Tough acetal homopolymer, DuPont D.E.N. Epoxy novolac resins, Dow Derakane Epoxy vinyl ester resins, Dow... 

Acetals are produced by Asahi Chemical (homopolymer Tenac, copolymer Tenac-C, and conductive copolymer Lynex-T ), BASF (copolymer Ultraform ), DuPont (homopolymer Delrin ), Mitsubishi Gas Chemical (copolymer lupital ). Polyplastics (copolymer Duracon in Asia) and a joint venture between Ticona and Daicel Chemical Industries, Ticona/Celanese AG (copolymer Celcon and Hostaform in Europe). Mitsubishi Gas Chemical, Polyplastics, and Ticona are (jointly, directly, or through affiliates) increasing acetal production capacity in the Asia/Pacific area, with a new 60,(XX) metric ton/year plant to be completed in 2004 in Nantong, Jiangsu province, north of Shanghai. ... 

Polyacetals prepared from formaldehyde are engineering thermoplastics, which have found use in traditional metal applications. Some trade names of these polymers are Delrin acetal homopolymer (DuPont) Celcon acetal copolymer (Celanese/Hoechst) Duracon acetal copolymer (Celanese and Diacel—joint venture) Tenac acetal homopolymer by Asahi Chemical in Japan and Ultraform acetal copolymer jointly by BASF and Degussa, in Germany. The polymers have the basic structure shown below ... 

There are two main types of acetal homopolymer and copolymer. The homopolymer version was invented by DuPont in the 1950s, with the trademark name of Delrin . The copolymer version came later, under the brand names Celcon , Hostaform , Ultraform , and Duracon . The distinctions between these two versions are subtle ... 

Throughout the remainder of this article the term homopolymer refers to Delrin acetal resin manufactured and sold by Du Pont the term copolymer refers to Celcon acetal copolymer resins (registered trademark of Hoechst Celanese Corporation). 

The first commercially available acetal resin was marketed by Du Pont in 1959 under the trade name Delrin after the equivalent of ten million pounds had been spent in research or polymers of formaldehyde. The Du Pont monopoly was unusually short lived as Celcon, as acetal copolymer produced by the Celanese Corporation, became available in small quantities in 1960. This material became commercially available in 1962 and later in the same year Farbwerke Hoechst combined with Celanese to produce similar products in Germany (Hostaform). In 1963 Celanese also combined with the Dainippon Celluloid Company of Osaka, Japan and Imperial Chemical Industries to produce acetal copolymers in Japan and Britain respectively under the trade names Duracon and Alkon (later changed to Kematal). In the early 1970s Ultraform GmbH (a joint venture of BASF and Degussa) introduced a copolymer under the name Ultraform and the Japanese company Asahi Chemical a homopolymer under the name Tenal. 

Polyformaldehyde. Polyformaldehyde or polyacetal is made by two different processes. Delrin is made from formaldehyde by anionic polymerization catalyzed by a tertiary amine. The homopolymer is end-capped with acetic anhydride. Celcon is made from trioxane cationic copolymerization using boron trifluoride catalyst and ethylene oxide (2-3%) as the comonomer. Boron trifluoride is a Lewis acid that associates with trioxane and opens up the six-membered ring. Ethylene oxide provides the end capping. Without an end cap, polyformaldehyde is thermally unstable and loses formaldehyde units. 

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. 

As already stated the two-thirds of acetal resins commercialized on the market are represented by copolymers prepared by the cationic process and one-third by homopolymers obtained anionically. The capacity of production can be estimated to be about 450,000 tons per year. The homopolymer is mostly produced by Du Pont under the trade name of Delrin... 

Acetal Copolymer (CELCON ) As with DELRIN , this is a highly crystalline polymer with excellent solvent resistance. It is somewhat more amenable to solvent cementing than the homopolymer, however. The solvent cement recommended by the manufacturer, Hoechst Celanese, is hexafluoroacetone sesquihydrate, available from Allied Signal, Inc. This solvent is a severe eye and skin irritant, however, and should be handled with care (7). 

---