Polyamide materials are hygroscopic—these materials take up moisture from a relative humid atmosphere or water, and release water into a dry atmosphere. For proper application designs, engineers want to be able to predict moisture uptake for polymides and know how it affects material performance in specific applications. With our Moisture Diffusion Tool, you can calculate the absorption and diffusion of moisture in polyamide materials as a function of time, position and temperature, for both 'as molded' and 'fully annealed' samples.
As an engineer, who designs application parts for a variety of markets, including automotive, electronics and electrical, energy, etc., you want to have the ability to predict moisture uptake for polyamides and how it affects the materials performance in specific applications. By using Envalior’s Moisture Diffusion Tool, you can calculate the absorption and diffusion of moisture in polyamide materials as a function of time, position and temperature, for both 'as molded' and 'fully annealed' samples. With this data you will know what material is best for specific applications and if you need extra precautions when storing the components before they are utilized.
Polyamide materials are hygroscopic—these materials take up moisture from a relative humid atmosphere or water, and release water into a relatively dry atmosphere. Polyamide properties depend on moisture content, so knowledge about water exchange is important. Also, when a polyamide part is exposed to an atmosphere with a certain relative humidity at a certain temperature, water concentration profiles over the thickness of the part, which develops over time and can be predicted with the tool.
You can quickly find out about the state of water uptake and release of a polyamide part as a function of time when you use our Moisture Diffusion Tool during the early stages of product development. With the tool you can calculate water uptake and release over time as well as overall water content for several commercial polyamide materials belonging to the Stanyl ®, ForTii ® and Akulon® product groups.
When using this tool, two types of challenges are solved. The first challenge relates to the polyamide part in an end application—you can predict the amount of water and its distribution over the part under specific application conditions. Then decide if the amount of water distribution is acceptable.
The second challenge relates to storing the parts between production (e.g. injection moulding) and utilizing them in an application. When storing parts at a warehouse, water uptake may occur over time. With our Moisture Diffusion Tool, you can calculate moisture uptake dependent on the specific storage conditions. With this data you can decide whether additional precautions are necessary, such as storing the parts in sealed bags, additional drying, etc.
The Moisture Diffusion tool is based on an advanced physical model in which water solubility and non-Fickian diffusivity are accounted for. The model uses a solver to evaluate the 1-D diffusion equation in time and space. The calculation time depends on the user input; if it takes too long, consider starting with a smaller number of cycles.
The model is based on a plate with a thickness much smaller compared to its width and height. To account for other sample geometries such as tensile bars, a correction is applied to the model. Although the tensile bars have a standard thickness, we allow the user to deviate from this value and specify a different thickness in the input field.
The accuracy of the fitted coefficients is in the order of 5% to 10% maximum. For 'as molded' samples, the prediction can be slightly less accurate due to a larger variation in crystallinity, depending on the processing conditions. This 'engineering accuracy' is indicated in the graph for each line by means of a semi-transparent confidence region.
Currently the Moisture Diffusion Tool can predict moisture changes going from dry to wet conditions or vice versa. Soon, the tool will be able to perform calculations for multiple- and cyclic conditions (multiple and periodic humidity and/or temperature changes). Plus, the EcoPaxx® product group will be added to the tool soon.
Alexander Stroeks is trained in chemical engineering and received his Ph.D. from Eindhoven University of Technology on a topic related to thermodynamics of polymer solutions and blends. After obtaining his Ph.D. he joined Envalior and was active in material properties related to R&D positions. He is currently principal scientist for functional properties of polymer materials. He is a material innovator based on solid material understanding. He is co-inventor of 50+ patents and examples of current interests are polymer barrier materials, advanced polymer modelling and polymer materials for novel energy solutions.
09 October 2023
