Why does nylon absorb water

Moisture absorbed onto the surface of the nylon resin or part can generally be removed by drying for 3 or 4 hours. However, for moisture that has absorbed more deeply, a much longer drying time is needed, sometimes up to 24 hours or more. In order for this moisture to be removed it is necessary to not only break the hydrogen bonds but to allow sufficient time for the water molecules to diffuse to the surface.

The water molecules that hydrogen bond between the nylon polymer chains cause the to move farther apart from each other. The strength and stiffness decrease while the impact and toughness increase. The amount of reduction in mechanical properties is dependent on the amount of moisture absorbed.

Amco Polymers offers a range of products within the various Polyamide sub-families. A wide range of additives, fillers and reinforcements can be incorporated to further enhance physical properties. Since PowerCore's moisture absorption is max. Conversely, the tensile strength of nylon 6 and 6.

For nylon 6. With increased moisture content, modulus of elasticity and other stiffness properties are also reduced. In estimating properties during practical use, refer to the properties of resins with the equilibrium water content under the same condition. Figure Relationship between relative humidity and the equilibrium water content of nylon 6 resins. Nylon 6 resins change the dimension by absorbing water.

The dimensional change should be carefully taken into account in designing the parts that demand dimensional accuracy.

This is what we refer to as dry-as-molded. From that point, the process of going from 0. Water is a plasticizer for nylon. Water has the same hydrogen bonding as nylon; when water enters a nylon part it has the same opportunity to become loosely attached to the nylon chain as does another nylon chain.

When the water molecule becomes positioned in this way, it forces the spacing between the polymer chains to increase. The greater the amount of moisture absorption the greater the volumetric expansion. Someone measuring parts will view this as an increase in the size of the part.

Typically the increase in size can equal 0. If the temperature increases, the moisture absorption levels will increase and the corresponding dimensional changes will become larger. Fillers and reinforcements will reduce this dimensional change, however even a highly filled nylon molded under optimal conditions will still expand by approximately 0. This makes it important that the processor and the end user define the conditions under which parts are to be measured for first-article approval.

While nylon represents the extreme where moisture absorption is involved, the vast majority of polymers absorb water at some level.