Common Defects in Rubber Products and Their Causes
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Release time:
Aug 31,2026
The most common defects in the production and inspection of rubber products are:
1. Sulfur deficiency 2. Sulfur excess 3. Air bubbles 4. Material shortage, insufficient mold filling 5. Frosting, oil blooming
1. Sulfur deficiency:
Rubber products exhibit softening, stickiness, poor elastic recovery, low strength, easy deformation, and fail to meet specifications for heat‑aging resistance.
Main reasons:
The vulcanization temperature is too low, the vulcanization time is insufficient, and the product thickness is excessive, leading to inadequate heat transfer; the dosage of the vulcanization system is inadequate or its dispersion is uneven; mixing is not uniform; and the rubber compound has been left standing for too long.
2. Over-sulfurization:
The finished product becomes hard and brittle, with reduced elasticity; its surface may exhibit scorching, cracking, or discoloration.
Main reasons:
The vulcanization temperature is too high and the curing time is too long; the amounts of vulcanizing agent and accelerator are excessive; during downtime while waiting for material, the rubber compound remains in the high-temperature zone for an extended period.
3. Bubbles:
Bubbles appear on the surface or within the material, compromising both its appearance and mechanical properties.
Main reasons:
Air is entrained during rubber compound mixing; excessive moisture in the compound leads to overly rapid vulcanization, preventing adequate gas venting; uneven preheating results in locally elevated moisture levels; and excessively high vulcanization temperatures can cause premature scorching, hindering gas escape.
4. Material shortage, insufficient mold filling ：
The product exhibits partial under‑molding, with issues at the edges and corners, thin walls, incomplete dimensions, and a weight that is on the light side.
Main reasons:
Insufficient injection pressure or injection speed; excessively low material or mold temperature, leading to reduced flowability and premature scorching; inadequate shot volume; poor mold venting, preventing air from escaping and hindering cavity filling; runner and gate dimensions that are too small, resulting in high flow resistance.
5. Blooming and oiling:
White frost, powder, or a waxy film may appear on the surface, adversely affecting appearance, adhesion, spray coating, and performance.
Main reasons:
In the formulation, sulfur, accelerators, antioxidants, waxes, plasticizers, and other ingredients exceed their solubility limits; mixing and dispersion are inadequate; the compound exhibits standing‑up or phase separation; vulcanization is insufficient; and poorly compatible additives have been used.
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Aug 31,2026
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Address: No. 39-6-1, No. 2, Gangxing Street, Economic and Technological Development Zone, Dalian City, Liaoning Province
Telephone:0411-88035937
Fax:0411-88035937
E-mail:yudongxin@dlbhxs.com
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