Production Polyoxymethylene

1 production

1.1 homopolymer
1.2 copolymer
1.3 fabrication

production

different manufacturing processes used produce homopolymer , copolymer versions of pom.

homopolymer

to make polyoxymethylene homopolymer, anhydrous formaldehyde must generated. principal method reaction of aqueous formaldehyde alcohol create hemiformal, dehydration of hemiformal/water mixture (either extraction or vacuum distillation) , release of formaldehyde heating hemiformal. formaldehyde polymerized anionic catalysis , resulting polymer stabilized reaction acetic anhydride. due manufacturing process, large diameter cross sections may have pronounced centerline porosity. typical example dupont’s delrin.

copolymer

the polyoxymethylene copolymer replaces 1–1.5% of –ch2o– groups –ch2ch2o–.

to make polyoxymethylene copolymer, formaldehyde converted trioxane (specifically 1,3,5-trioxane, known trioxin). done acid catalysis (either sulfuric acid or acidic ion exchange resins) followed purification of trioxane distillation and/or extraction remove water , other active hydrogen containing impurities. typical copolymers hostaform celanese , ultraform basf.

the co-monomer typically dioxolane ethylene oxide can used. dioxolane formed reaction of ethylene glycol aqueous formaldehyde on acid catalyst. other diols can used.

trioxane , dioxolane polymerized using acid catalyst, boron trifluoride etherate, bf3 oet2. polymerization can take place in non-polar solvent (in case polymer forms slurry) or in neat trioxane (e.g. in extruder). after polymerization, acidic catalyst must deactivated , polymer stabilized melt or solution hydrolysis remove unstable end groups.

stable polymer melt compounded, adding thermal , oxidative stabilizers , optionally lubricants , miscellaneous fillers.

fabrication

pom supplied in granulated form , can formed desired shape applying heat , pressure. 2 common forming methods employed injection molding , extrusion. rotational molding , blow molding possible.

typical applications injection-molded pom include high performance engineering components (e.g. gear wheels, ski bindings, yoyos, fasteners, lock systems) , material used in automotive , consumer electronics industry. there special grades offer higher mechanical toughness, stiffness or low friction/ wear properties.

pom commonly extruded continuous lengths of round or rectangular section. these sections can cut length , sold bar or sheet stock machining.