June 28, 2020

Effective measures to solve the oil drop of low hardness soft plastic parts after oil injection

For low hardness PVC and rubber injection parts with a hardness value less than 80 degrees (Shore hardness, GB / T2411—2008), the problem of oil loss has always been a quality problem that is difficult to control and guarantee during production in the oil injection department. The lower the hardness, the more It is difficult to guarantee that the oil will not fall. When the hardness is lower than 70 degrees, the problem of oil loss seems to be difficult to control and often occurs. At this time, people often blame the bad weather, the injection molded parts have mold release agents, or they have been placed for too long, etc., causing the oil injection parts to drop oil, so there has been no good solution to ensure low hardness The problem of oil loss of soft plastic parts does not occur from time to time.

Generally speaking, the problem of oil loss of soft plastic parts is mainly caused by a layer of oil on the surface of the injection molded parts that is difficult to remove. Some of this layer of oil is the residue of the release agent, and the more important is the oil that leaks from the inside of the injection molded part to the skin. It is fused with the injection molded part, so it is very difficult to clean. The more traces, the more serious the problem of oil loss. Therefore, to solve the problem of removing oil traces on the surface of injection molded parts is the main direction to solve the problem of oil loss of soft plastic parts with low hardness.

In many cleaning tests, I have also tried adding 70% water and other solvents into various cleaning agents to clean the 70-degree PVC injection parts, but it is not helpful for the injection parts with serious oil marks on the surface. The injection parts just produced, oil The slightest trace will have a certain improvement effect, but it cannot be an effective and stable solution, and the oil drop problem will occur from time to time. Experiments have shown that using Tina water to clean the surface of PVC injection molded parts with a hardness of less than 70 degrees has achieved satisfactory results.

Tianna water (the main component is xylene, also known as “banana water”) is a solvent that is very corrosive to plastics, whether it is PVC, or ABS and PC materials can be dissolved by it. It is this feature that solves the problem of cleaning the oil stains on the surface of soft plastic PVC injection parts.

The soft plastic PVC injection parts are cleaned with Tina water. The purpose is to make the Tina water dissolve the surface layer of the injection part with a lot of oil traces, so that the plastic part exposes a clean oil-free surface layer. How to dissolve only the oily surface layer without destroying the surface quality of the injection molded parts has become the key to solving the problem.

After many tests, the technicians finally found a simple, effective, and easy-to-produce solution, which is to take the injection molded parts out and put them in clean water for a few seconds. When the injection molded parts are immersed in Tianna water, they will be immersed in the water immediately, so that Tianna water can just dissolve the oil-bearing surface layer, and it has lost the ability to corrode the surface of the injection molded parts before it can be further dissolved. The purpose of protecting the surface quality of injection molded parts. At the same time, the residual oil traces mixed in the water of Tianna were also cleaned into clean water. The injection molded parts exposed a clean and non-destructive shiny surface. After the plastic parts were taken out to dry, they could be used for oil spray production. At this time, you can also see that the edge of the water basin filled with water is covered with a lot of creamy oil removed from the surface of the injection molded part.

It should be emphasized that in the operation of cleaning the surface of injection molded parts, the time of immersing the water in the sky is very important, generally controlled within 1 to 3 seconds. After a long time, the surface of the injection molded part will be dull and white, too fast, the cleaning effect is not thorough enough. Therefore, it is necessary to study the best soaking time according to different injection parts. If the matte whitening of the surface of the injection molded part is not easy to control, you can add an appropriate amount of cyclohexanone in Tianna water to improve the ability to resist whitening and facilitate the operation control of the production. If the solvent is prepared and the operation is well grasped, it can even be placed on the table carefully without being put in water after immersing the injection molded parts, and it can be used for oil spray production after drying.

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Injection Molding, Plastic Mold Case, Plastic Molding Design, Plastic Parts
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