There are two general types of acetal resins available: Acetal homopolymer and acetal copolymers. Each type of acetal has its own set of advantages and disadvantages. Acetal (polyoxymethylene, POM) is a thermoplastic polymer commercialized in the early 1960’s. This material is produced through the polymerization of formaldehyde.ACETAL HOMOPOLYMER resins are currently made by the DuPont Company under the trade name Delrin®. Acetal homopolymers offer the following advantages over acetal copolymers: Acetal copolymer is more resistant against hydrolysis, strong alkalis and thermal-oxidative degradation than the acetal homopolymer.
Stiffer than acetal copolymers. Higher flexural modulus at room temperature and elevated temperature applications.Higher impact strengths at room temperature levels and low temperature levels. Tensile strength is approximately 10-15% higher than similar copolymers. A little greater constant usage temperature level than copolymer (95 ° C vs. 90 ° C). Somewhat harder than copolymer acetals, therefore providing the homopolymer acetals a lower coefficient of friction.POM Acetal Copolymer( Ultraform ®, Celcon ® )is made by numerous companies consisting of BASF and Ticona. Acetal copolymers have the following benefits over homopolymer: Enhanced dimensional stability over equivalent homopolymer solutions due to its lower level of crystallinity. Much better chemical resistance with high pH (standard) services. Lower centerline porosity than homopolymer in extruded shapes.In most cases, acetal homopolymer and copolymer can be interchanged because lots of material residential or commercial properties are within roughly 10% of each other. Typical physical residential or commercial properties are displayed in the accompanying table. Maybe the most significant difference between homopolymer and copolymer acetal connects to the phenomenon known as centerline porosity. It is most popular in extruded parts, especially thick piece and big size rod stock. Aesthetically, it is a whiter shaded region around the center part of a rod, which extends down the whole length. In piece, porosity looks like a line along the center of each cut edge. In some cases, the piece might appear to be laminated or glued together. Excessive centerline porosity is undesirable for the following reasons: Cosmetic – inconsistent color appearance in completed parts. Compromises structural stability. Present paths for leakage of gas and liquids. Supply locations where the bacteria can grow in food processing applications. Acetal Copolymer vs Delrin® Acetal Homopolymer, the cause of the porosity is out-gassing. During the extrusion process, the outdoors skin of the shape cools prior to the interior region. As the interior material cools, there is a matching decrease of volume. Considering that the total volume change of the shape is restricted due to the strengthened skin, voids form to compensate for the loss of interior volume.Here is a fantastic video by Dupont discussing the advantages of using Dupont Delrin Homopolymer:Acetal copolymers have the following benefits over homopolymer: Enhanced dimensional stability over equivalent homopolymer formulations due to its lower level of crystallinity. Lower centerline porosity than homopolymer in extruded shapes.In most cases, acetal homopolymer and copolymer can be interchanged since lots of product homes are within roughly 10% of each other. Perhaps the most substantial distinction between homopolymer and copolymer acetal relates to the phenomenon known as centerline porosity.