Delrin 150 Plate

Acetal homopolymer - POM-H - is the stronger and stiffer of the two acetals, and the one specified when a machined part has to carry load and hold its dimension. Tensile strength around 10,000 psi against the copolymer's 8,800, a higher melting point at 347F, better fatigue resistance, and the same low moisture pickup that lets a part machined dry stay the size you cut it.

The honest trade, because this is the one place buyers go wrong. Homopolymer is stronger; copolymer survives more. Homopolymer runs pH 4 to 9 and resists hydrolysis to 60C. Copolymer runs pH 4 to 13 and to 85C. So for caustic cleaning, hot water, steam or a sanitized wash-down line the copolymer is the right material and we would rather sell you that than replace this. Homopolymer is also the more porosity-prone of the two in heavy sections. Where the duty is mechanical and dry, this is the better plate.

On porosity, because it decides whether a part can hold pressure. Centerline porosity in thick sections is a specified characteristic rather than a defect: ASTM D6100 sets porosity levels and gives a dye-penetration test, so you can specify what you need rather than hope. Homopolymer is the more susceptible of the two types and it gets worse as the section gets thicker. If the part seals or holds pressure, tell us the thickness and we will specify to D6100 or steer you to the copolymer.

The warning worth more than any number on this page: CHLORINE ATTACKS ACETAL AT 3 TO 5 PPM. That is ordinary municipal tap water and ordinary sanitizing concentration. Acetal in a chlorinated circuit, a pool system or a sanitized wash-down line will craze and fail, and almost nobody prints this. Strong acids and strong bases attack it too, and the homopolymer's window is the narrower one. If chlorine is anywhere in the application, ask us before you machine it.

Machining notes. It is among the easiest engineering plastics to machine well and takes a genuinely fine finish - sharp tools, positive rake, generous chip clearance, coolant optional on light cuts. Thermal expansion is high for a plastic, so a part machined warm measures differently cold; let heavy sections normalize before the finishing cut. Homopolymer is the harder and more brittle of the two acetals, so inside corners want a radius.

One note on the black. Carbon black genuinely does screen ultraviolet in acetal at the loadings used, and one mill states plainly that its black is weather resistant where its natural is not. But standard black pigmented plate is still not a weathering grade and dedicated UV grades exist, so for sustained outdoor service ask us rather than assuming the color is doing the work.

On food contact, stated precisely rather than claimed. The applicable clearance for this material is 21 CFR 177.2480, which covers polyoxymethylene HOMOpolymer - a different section from 177.2470, which covers the copolymer, and the industry routinely cites whichever it has to hand. Two things follow. The clearance belongs to the resin and its pigment as made, so what belongs in your file is the mill certificate for the lot you are shipped, and we will get it rather than asserting compliance here. And the FDA acetal clearances cap use temperature at 250F, below where the material itself gives up.

Safety, and this is specific rather than boilerplate. Acetal evolves FORMALDEHYDE above 446F and also on contact with strong acids or strong bases. OSHA's permissible exposure limit is 0.75 ppm over eight hours with a 2 ppm short-term cap, and it is a sensitizer, so repeat exposure matters. Keep tools from overheating the cut, use local exhaust, and never let acetal swarf mix with PVC, because halogenated polymers can trigger sudden formaldehyde release from it. Ask us for the manufacturer's Safety Data Sheet and work to it rather than to this paragraph.

How this is sold: by the square foot, cut to the size you need. The mills supply plate in full sheets and we cut from them, so give us the dimensions and we will quote the cut piece rather than making you buy a whole sheet.