What plastic does not absorb water?

Plastics That Resist Water Absorption

When choosing a material for environments exposed to moisture, one key factor is water absorption. Most plastics will absorb at least a small amount of water, which can affect their mechanical properties, dimensions, and long-term durability. However, certain polymers stand out for their exceptional resistance.

PTFE (polytetrafluoroethylene) is unique—it's the only plastic known to have virtually zero water absorption. This makes it ideal for critical applications in aerospace, medical devices, and chemical processing where moisture sensitivity is a concern.

Besides PTFE, several high-performance engineering plastics exhibit very low water absorption. These include PI (polyimide), PEEK (polyetheretherketone), PPS (polyphenylene sulfide), PSU (polysulfone), PPSU (polyphenylsulfone), and PEI (polyetherimide). These materials are often used in demanding environments like automotive or industrial systems due to their stability and strength—even when exposed to humidity.

Other common polymers like PVDF, PET, PPE, PP (polypropylene), and PE (polyethylene) also absorb minimal water, making them suitable for outdoor or wet applications. Plastics such as POM (acetal), PA12 (nylon 12), PC (polycarbonate), and ABS have slightly higher but still low absorption rates, balancing performance with cost-effectiveness for consumer goods and enclosures.

In practical terms, selecting a low-absorption plastic means better dimensional stability, reduced risk of swelling or cracking, and longer service life—especially in humid or submerged conditions. While no material is perfect for every use, understanding these properties helps engineers and designers make smarter choices.