Surfaces: The Invisible Universe We Look Upon Every Day But Never Really See: Chapter 3 – Paradox of Hydrophobic / Hydrophilic Nylon

Is Nylon Hydrophobic, Hydrophilic or Maybe Both?

In a recent posting on LINKEDIN Scott Sabreen Owner-President, The Sabreen Group Inc. Initiated the following discussion:

 

Nylons are inherently difficult to bond because they are hydrophobic, chemically inert and possess poor surface wetting. …

Nylons are hygroscopic and will absorb moisture in excess of 3 percent of its mass of water from the atmosphere. Moisture, in and of itself, creates adhesion problems.  …

 

Hold on, on the face of it the above remarks would seem to be mutually contradictory.  Is nylon hydophobic or hydrophilic?

The resolution of this apparent paradox comes in recognizing that the hydrophobic behavior of nylon is a surface property and the hydrophilic behavior is a bulk property.

Since nylon is an organic polymer it has a relatively low surface energy as do most polymers.  This is a consequence of the surface chemistry and surface physics of polymers and other organics as discussed in the previous edition of this blog.

However the amide groups in the nylon chain attract water and they give rise to the hydrophilic behavior of this material in regard to BULK ABSORPTION of water.  A number of other polymers such as the polyimides also behave in a similar manner.

So in the bulk nylon can behave as a hydrophilic material but on the surface it can exhibit hydrophobic behavior. Just another hidden property of surfaces that make them both tricky and fascinating to study.

The author invites any inquiries or comments.

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