During the vulcanizing, bubble is a common quality problem. It has bad influence to the appearance and cause serious effect to the quality. Worse more, bubble problem is a huge impact to company’s brand and the clients may not trust you.
According to the test and analyze, the reasons of bubble problem are many aspects. The most important reasons are raw material, rubber mixing technology, operation skill, vulcanize equipment and mould.
1. The moisture and volatile matter of natural rubber are beyond the standard
2. The moisture in chemical material and additive increases during the storage and dispense
3. The steel wire and cord get damp; the mucilage on the steel wire is not dry
4. The moisture regain of cord is high
Parts of semi-finished product
1. Uneven dispersion of additives during the rubber mixing
2. The low temperature during mixing cause the moisture volatilizes not completely
3. The rubber place time is not enough or put into production without placement
4. The cooking of rubber material is not even and the product surface is not smooth
5. During the cooking, rubber material is covered with air. There will be air inside the extruded tube
1. The temperatures of roller, rubber charging and extruding are unqualified. This cause bubble in the semi-finished products
2. Much of air between the calender rubber, fabric glue and cord. It’s hard to discharge completely during the vulcanize
3. The tolerance of thickness and width for semi-finished product is large and it affect the flow in the mould
4. Rubber material twist and cause air harbor and then cause bubble
5. When gumming, the gum is only on the surface. The air content is high in the steel wire and the gap is large. So there will be air when stick rubber piece.
6. Low pressure when vulcanize makes low compactness of rubber material, then cause bubble.
7. If the temperature and technology can’t meet the requirements, the bubble appears
Equipment and mould
1. Large deviation of press vulcanizer temperature control system. High temperature reduce the material flowing time.
2. Mould damage on the surface and influence the material flow
3. Dirties on the mould affect the mobility of rubber material
4. The exhaust line and exhaust holes are not reasonable. The thin exhaust line and small holes have bad influence on air exhaust.
These are the reasons cause bubble during vulcanizing. Follow EverFlex and learn how to solve the problem next.