Rubber Engineering Parts Sourcing: Learn about the Bubble defects that appears in the rubber. We has experienced in practice and would like to contribute some information, as follows:
Appearancee: Bubble defect is very common for rubber compounds with low hardness about <40 Shore A (high oil content).
Bubbles can come from different sources and there are different variables (most controllable) that will affect the size and quantity of bubbles generated.
The following recommendations help improve the elimination of Air Bubble in rubber:
1. Pressing Machine: Release the air in several times on the press to allow air bubbles to escape.
2. Rulo-making technology: with compound technology, it means that the sheets are placed on top of each tooling/mold. There are small spaces between the sheets and the rolling of the rulo. Therefore, it is necessary to perform Tattoos (puncture) on the surface of the rubber sheet so that the air can easily escape. With extrusion technology, the bubble problem solved.
3. Creating semi-finished workpieces [BTP]: Creating BTP billets on the extruder will completely eliminate air bubbles in the rubber compound.
4. Compound: Pay attention to the NR rubber compound, meaning that after rolling, it should be stable to cool for at least 4 hours before pressing.
5. Compounding: Check the surface (cross-section) of the compound, if there are any air inside, it should be back to the rolling process.
6. Presses with vacuum: Vacuum when shaping vulcanizing products in molds, contributing to solving air bubbles.
7. Mold: Make a flash slot [flash chanel] to release over-compound on the mold, air will easily escape.
8. Moisture comes from raw materials and additives: During vulcanization, moisture in addtitives easily evaporates and create air bubbles for rubber products. Moisture is often present in rubber (especially natural rubber), accelerator, Zinc and aging additives … Therefore, it is necessary to check the addtitives that can be mixed.
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