Plastics and Water Absorption
Last updated : 2026/7/27
Key Takeaways
Water absorption varies by plastic, with nylon-based resins absorbing significantly more moisture than most other materials.
Moisture absorption causes plastics to swell, reducing dimensional stability and affecting part accuracy.
Water absorption also lowers the glass transition temperature (Tg), reducing a plastic’s thermal and mechanical performance.
Overview
If you’ve noticed plastic parts changing dimensions depending on the environment, or components losing strength in humid conditions, the cause may be water absorption in the material.
High Water Absorption Plastics
Most plastics absorb some moisture, though the amount varies by material. Nylon-based resins are particularly prone to water absorption, while others take in very little.
Nylon resins absorb more moisture due to their molecular structure. They contain amide groups (–CONH₂), which are hydrophilic, meaning they readily attract and interact with water.
Effects of Water Absorption
When plastics absorb moisture, they swell, leading to dimensional changes. Materials with higher water absorption have lower dimensional stability.
In addition, moisture uptake lowers the glass transition temperature (Tg), which can affect the material’s thermal and mechanical performance.
Plastic CNC Machining at Yumoto Electric
Yumoto Electric delivers high-quality components fast, worldwide. We provide precision machining for a wide range of engineering plastics, including PEEK, PPS, MC Nylon, and POM.
If you’re unsure about material selection or machining methods, we offer complimentary consultations to help optimize your design and production. For any questions, please feel free to contact us.
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