Rubber products bubble is often encountered in the production process, the surface of the product bubble, not only affect the appearance, but also affect the quality. There are many reasons for molding products to produce bubbles, including vulcanization parameters, mold structure, operation process, rubber containing water or gas, the thickness of products, etc., so how to solve it in the actual production, the following and we share the common reasons and solutions.

1. Analysis of the causes of bubbles in molded products:

The main reasons are:

1. The problem of materials is that there is moisture in the process of mixing, storage and use of rubber materials. The moisture is not eliminated, resulting in bubbles or moisture caused by weather changes. Most of the reasons may be that there is a problem with the raw materials. Try changing another batch of materials. Add exhaust or moisture absorbent (calcium oxide) to the formula.

2, there is gas wrapped in the rubber material, the gas is not easy to exclude, vulcanization produce bubbles.

3. Improper setting or blockage of the exhaust hole of the mold will also produce bubbles, and the exhaust is not properly discharged (improve the exhaust groove of the rubber material, and try to simplify the deconstruction of the mold without leaving dead corners).

When raw materials are in rubber refining, air is wrapped inside the material, resulting in the process of processing, the material and air enter the mold together. If there is no exhaust groove in the mold or no exhaust process is set in the processing, the air is easily trapped in the mold, resulting in bubbles or air holes in the product.

4, the production of rubber products, vulcanization after bubbles, may be the problem in the rubber formula, the material is reasonable, appropriate to add help to exhaust the material (recycled rubber, rubber powder, exhaust agent, calcium oxide, etc.).

5. Poor bonding of rubber and metal will cause a large amount of gas in the bonding part.

Two, rubber products vulcanization bubble reasons

1, rubber mixing is not uniform, the operator is not standard. In accordance with the reasonable feeding sequence and thin pass times and parking after curing back pressure process.

2, rubber film parking is not standard, the environment is not healthy. The management is not standardized. Foreign impurities.

3, the material has water (add calcium oxide when mixing)

4, curing is not enough, not ripe looks like bubbles.

5, curing pressure is insufficient.

6, curing agent impurities are more, small molecule impurities into decomposition in advance, bubble residue products

7. The exhaust design of the mold itself is unreasonable, and the gas can not be discharged in time when the rubber material is pressed.

8, the product is too thick, the rubber material is too little, the rubber heat transfer is slow, the surface vulcanization, the rubber fluidity decreases, resulting in lack of material, so it may produce bubbles. Adjust the vulcanization rate, not easy to be too fast.

9. The exhaust in the vulcanization process is not well discharged. Improve exhaust frequency and exhaust time interval.

Formula problem, vulcanization system to improve. Low temperature slow speed (relative) is recommended.

Solution: improve curing pressure and time

A, prolong the curing time or improve the curing speed. Reasonable vulcanization temperature range.

B. Thin pass several times before vulcanization. Park and mature and then back pressure.

C, vulcanization exhaust more times. Exhaust time interval is reasonably arranged.

D, reduce the meni of the mixed rubber, choose the rubber material with low air tightness (raw rubber or formula to reduce air tightness).

11, poor rubber-metal bonding will cause a large amount of residual gas at the bonding site, and gas contraction when pressurized. Once the pressure is removed and the gas diffuses, bubbles form between the rubber and the metal, which are thinner and larger in area.

Three, rubber product surface bubble analysis

1, there is water (mixing with calcium oxide);

2, not fully vulcanized, not ripe looks like bubbles; Appropriate extension of curing time to see the effect

The vulcanization of products is not sufficient, resulting in large bubbles on the surface of rubber products, which are honeycomb and spongy when cut

1, prolong the curing time, improve the curing temperature, to ensure that there is enough pressure curing;

2, adjust the formula, improve the vulcanization speed;

3 vulcanizing agent more impurities, small molecule impurities into decomposition in advance, bubble residue products; Park below the back pressure for 24 hours.

4. The exhaust design of the mold itself is unreasonable, and the gas cannot be discharged in time when the rubber material is pressed; Appropriate increase of rubber material exhaust hole, conducive to gas discharge.

5. Poor dispersion; Add dispersant, park back pressure or feeding sequence.

6. The plasticizing time is long, and there are bubbles when the product is vulcanized. Reduce the high temperature of the rubber material has been pressed back and forth on the roller times.

Three, there is gas wrapped in the rubber material, the gas is not easy to exclude, vulcanized with the rubber material, so that bubbles appear on the surface of the product

1. Increase the number of air letting after mold closing;

2. Vacuum the mold;

3, improve the temperature of the mixing glue;

4. Rubber with high Mooney viscosity is used;

Mooney viscosity reaction rubber processing performance and molecular weight and distribution range width.

Mooney viscosity high adhesive is not easy to mix evenly and extrusion processing, its high molecular weight, wide distribution range. Mooney viscosity low rubber easy to stick roller, its low molecular weight, narrow distribution range.

Low Mooney viscosity results in low tensile strength of vulcanized products.

Mooney viscosity-time curve can also be used to determine the curing properties of rubber.

5. Break the air bubbles on the rubber material before feeding; (More primitive)

6. Improve the mixing process of the mixer and try to avoid gas mixing with rubber material;

7, improve the injection conditions, so that the rubber can enter the mold cavity slowly; (Generally not desirable, easy to produce lack of glue)

8. Improve the exhaust groove and overflow groove of the mold;