--- title: Moisture Absorption, Swelling in Nylons, except Cast Nylon Powercore description: Moisture absorption, a key factor to consider during nylon material selection --- 250 Herbert Avenue Closter, New Jersey 07624 U.S.A. 1-877-218-2650 [![intech.power.logo.Power of knowledge.](https://www.intechpower.com/hs-fs/hubfs/intech.power.logo.Power%20of%20knowledge..jpg?length=300&name=intech.power.logo.Power%20of%20knowledge..jpg "intech.power.logo.Power of knowledge.") ](https://www.intechpower.com/) [![Browse Our Products](https://no-cache.hubspot.com/cta/default/62516/08b25f71-daf5-4226-916d-2693bd171a1d.png)](https://cta-redirect.hubspot.com/cta/redirect/62516/08b25f71-daf5-4226-916d-2693bd171a1d) [![Browse Our Products](https://no-cache.hubspot.com/cta/default/62516/08b25f71-daf5-4226-916d-2693bd171a1d.png)](https://cta-redirect.hubspot.com/cta/redirect/62516/08b25f71-daf5-4226-916d-2693bd171a1d) November 25, 2009 # Moisture Absorption, Swelling in Nylons, except Cast Nylon Powercore Written by [Simon Barrell](https://www.intechpower.com/blog/author/simon-barrell) Moisture absorption is a key factor to consider during nylon material selection. Design engineers need to take account of the application and tolerances because, machined component dimensions for a particular nylon grade will change if they were originally designed for a dry environment but are then used in a humid location. Moisture is absorbed by the part, and at some point when it reaches equilibrium, swelling can occur, and the fact that the dimensions of the part are subsequently altered increases the likelihood of premature part failure. Injection molding, extrusion, and casting can all be used to form nylon, and the process used will influence material properties. In the case of injection molding, nylon is subjected to high compression and decompression within a short period of time. Correct mold design, timing, and precise pressure control are vital, and accurate thermal history for the part when both inside and outside of the mold should be maintained. If water is present where extrusion is used in forming a part, severe problems can result. Therefore, moisture content and cooling rates should be monitored rigorously as they will both influence the physical properties of the extrusion. Extruded rods or slabs can also be susceptible to shrinkage voids that are caused while the inside is in a molten state but the exterior surface begins to solidify. While the interior cools and shrinks under thermal contraction and crystallization, a void forms as the exterior no longer contracts. One solution is for extruders to use controlled water or vacuum quenching to cool formed parts. Note that even where forming processes can be precisely controlled, physical properties and dimensions may change over time when exposed to changing transport and storage conditions.   ![Chart - Dimensional change polyamides versus moisture](https://static.hsstatic.net/BlogImporterAssetsUI/ex/missing-image.png) The diagram shows moisture absorption causes swelling which results in up to 3.3% dimensional change in the nylon 6 family. When designing with nylon 6 or 6/6, this has to be taken into consideration, for example, when calculating backlash in gears, or when storing precision parts for prolonged periods of time in changing environments. For cast nylon powercore such change is negligible, even when permanently immersed in fuels, oils, and chemicals. Tag(s): [cast nylon 12](https://www.intechpower.com/blog/tag/cast-nylon-12) , [moisture absorption](https://www.intechpower.com/blog/tag/moisture-absorption) , [calculating backlash](https://www.intechpower.com/blog/tag/calculating-backlash) , [dimensional change](https://www.intechpower.com/blog/tag/dimensional-change) , [forming nylon](https://www.intechpower.com/blog/tag/forming-nylon) , [gear backlash](https://www.intechpower.com/blog/tag/gear-backlash) , [injection molding](https://www.intechpower.com/blog/tag/injection-molding) , [material shrinkage](https://www.intechpower.com/blog/tag/material-shrinkage) , [moisture content](https://www.intechpower.com/blog/tag/moisture-content) , [polyamides](https://www.intechpower.com/blog/tag/polyamides) [mailto:?subject=Check%20out%20https://www.intechpower.com/blog/blog/bid/48151/moisture-absorption-swelling-in-nylons-except-cast-nylon-12](mailto:?subject=Check%20out%20https://www.intechpower.com/blog/blog/bid/48151/moisture-absorption-swelling-in-nylons-except-cast-nylon-12) [gear design](https://www.intechpower.com/blog/tag/gear-design) ** 3 minute read | March 22, 2013 ## [Large Underwater Gear Highlights Nylon's Moisture Resistance](https://www.intechpower.com/blog/blog/bid/113997/large-underwater-gear-highlights-nylon-s-moisture-resistance) Wear and moisture resistance are two recurring themes in the engineering problems solved by Intech Power-Core™. Oftentimes,... [Read More](https://www.intechpower.com/blog/blog/bid/113997/large-underwater-gear-highlights-nylon-s-moisture-resistance) [cast nylon 12](https://www.intechpower.com/blog/tag/cast-nylon-12) | December 9, 2009 ## [Effects of Moisture on the Tensile Strength of Nylon 12](https://www.intechpower.com/blog/blog/bid/48148/effects-of-moisture-on-the-tensile-strength-of-nylon-12) [Read More](https://www.intechpower.com/blog/blog/bid/48148/effects-of-moisture-on-the-tensile-strength-of-nylon-12) [washdown application](https://www.intechpower.com/blog/tag/washdown-application) ** 3 minute read | January 16, 2014 ## [Cast Nylons Replace Structural Aluminum and Gluing Delrin Parts](https://www.intechpower.com/blog/blog/bid/118164/cast-nylons-replace-structural-aluminum-and-gluing-delrin-parts) Robotic arms for e-coat systems have traditionally been made from aluminum, whose strength-to-weight ratio made it seem... [Read More](https://www.intechpower.com/blog/blog/bid/118164/cast-nylons-replace-structural-aluminum-and-gluing-delrin-parts) ## Subscribe to email updates Copyright © 2026 Intech Corporation. All Rights Reserved. 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