Understanding Migration and Precipitation in TPE/TPR Blends
Time of issue:2024-12-28
Translation:
I. Concepts of Migration and Precipitation
(1) Migration: The process by which certain substances in a blended material system gradually migrate from the interior to the surface over time is called migration.
(2) Precipitation: The substances undergoing migration that渗出to the surface of the product are referred to as precipitation. This is somewhat similar to the crystallization of a solute in a solution as the temperature decreases, causing it to precipitate in the form of solid crystals.
II. Migration and Precipitation in TPE/TPR Blend Systems
Both TPE and TPR are blended materials. In their blend systems, migration and precipitation also exist. Here is a brief interpretation for you.
Many times, formula designers, with good intentions, actively utilize migration and precipitation to improve certain performance deficiencies of materials. However, too much of a good thing can be problematic. If the addition amount of additives is not controlled well, excessive migration and precipitation can occur, which is undesirable.
For example, sometimes to improve the slipperiness, processability, and demolding properties of materials, certain additives may be incorporated into the system. When the addition amount of these additives is properly controlled, they can improve the deficiencies of material performance. However, if the addition amount exceeds the limit, the additives will precipitate to the surface of the material, affecting product performance.
III. Analysis of Common Issues
(1) Sticky Surface of High-Hardness TPE Products: This is caused by the precipitation of processing oil. High-hardness TPE has poor oil absorption capacity. When the oil charging exceeds the proportion, the oil will precipitate from the system.
(2) Oil Leakage from Conventional TPE/TPR Materials: This is caused by excessive oil charging, poor oil-locking properties of the base material, or inadequate oil charging. Corresponding improvements and adjustments can be made.
(3) Sticky Surface of Wire and Cable Products: The reason is similar to the first analysis above. Additionally, excessive addition of certain additives that precipitate to the surface can also cause surface stickiness.
(4) Precipitation of White Powdery Substances on the Surface of TPE/TPR Products: This is caused by the excessive precipitation of compatibilizers or certain white powdery additives.
(5) Oil Leakage on the Surface of Overmolded Products: This is caused by the precipitation of synergistic additives in the TPE blend system.
IV. Can Precipitation in TPE Products Be Treated?
If surface precipitation occurs, there is generally no effective solution. Wiping off the precipitated substances will only result in their reappearance after a while. If it is determined which substance is precipitating, one can try to find a solvent that can dissolve that substance (while not affecting other components of the TPE system) and soak the product in the solvent for 15 to 60 minutes to allow it to dissolve fully. This method may be relatively effective but is still a laborious and time-consuming last resort.
V. Conclusion
Controlling the migration and precipitation of TPE materials and products is an important aspect of formula development and pelletizing processes. Among them, the control of additive addition amounts is crucial. It is important to conduct careful experiments in the laboratory to analyze and determine the most suitable addition ratio to form a mature formula before launching it into the market.
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