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How should impurities and black spots on the surface of a silicone tube be handled?

2022-01-14

1. Causes of impurities and black spots on the surface of silicone tubing:
1: Raw materials cause defects. In the production of silicone tubes and strips, 20% of black spots are attributable to black‑spot impurities in the raw materials.
2: Excessive black specks can result from secondary rubber compounding. Typically, when compounded rubber is stored for an extended period, the vulcanizing agent loses its effectiveness; in such cases, the compound must be re‑compounded and a fresh dose of vulcanizing agent added. Black specks or other impurities may also appear during secondary compounding.
3: Caused by the molding process. During production, if the machine’s venting stroke is too long, black specks and impurities may be drawn in during venting.

II: Methods for addressing impurities and black spots on the surface of silicone tubing:
1: Before compounding the rubber compound, it is necessary to carefully inspect the product for black specks or other impurities.
2: During the secondary rubber compounding process, contamination of the rubber compound from the operator’s hands, the vulcanizing agent, or the ambient air may occur, resulting in black spots and impurities in the molded, vulcanized products.
3: During the molding process, both the area surrounding the machine and the indoor environment must be strictly controlled. Excessive debris on the mold should also be closely monitored; such issues are particularly common with newly commissioned molds. Therefore, most silicone‑product manufacturers first sandblast or apply a Teflon coating to the molds, followed by thorough cleaning to keep them pristine—this effectively addresses the critical defect of black spots. In the material‑weighing stage, ensure your hands are clean and thoroughly clear the workbench and all nearby surfaces of anything that could introduce contaminants or black spots. Human error is a major contributor to surface‑appearance defects, so it’s essential to maintain personal organization and adopt disciplined operating procedures to prevent black‑spot defects.

How to choose the right silicone vulcanizing agent?

None

Precipitated silica is a high-tech inorganic fine chemical product.

White carbon black, also known as silica, is scientifically termed precipitated hydrated silica. It is a high‑tech inorganic fine chemical product whose main constituent is SiO₂. Its physical properties resemble those of carbon black, appearing as a highly dispersed white amorphous powder or flocculent powder; it is also processed into granular forms for commercial use. Lightweight, with an original particle size below 0.3 μm and a relative density ranging from 2.319 to 2.653, it has a melting point of 1750°C. It is insoluble in water and most acids, but absorbs moisture from the air, forming hygroscopic fine particles. It is soluble in caustic soda and hydrofluoric acid, while remaining inert to other chemicals; it does not decompose at high temperatures nor does it burn. It is chemically inert toward substrates, active ingredients, and additives, and exhibits excellent compatibility with many active components commonly used in vitamins, hormones, fluorides, antibiotics, enzyme preparations, and cosmetics. It possesses high electrical insulation properties. Owing to its porosity and large specific surface area, it demonstrates strong dispersibility in raw rubber and imparts superior reinforcing performance in rubber compounds. Surface‑modified hydrophobic silica readily disperses in oils, rubbers, and plastics as a reinforcing filler, significantly enhancing mechanical strength and tear resistance. Due to variations in manufacturing processes, the physical and chemical characteristics, as well as the microstructure, of silica may differ, leading to distinct application areas and performance outcomes.

2022-02-19

Do you know the types and properties of silicon dioxide?

The reinforcing fillers used in silicone rubber are primarily synthetic silica, also known as precipitated silica. Precipitated silica is classified into fumed silica and precipitated silica.

2022-02-19

What method is used for the high-temperature surface treatment of precipitated silica?

Surface high‑temperature treatment involves subjecting precipitated silica to elevated temperatures to remove adsorbed molecules—such as water and other low‑molecular‑weight species—from its surface. While this approach can modestly improve certain vulcanization properties, the effect is not particularly pronounced. Surface chemical treatment, on the other hand, entails reacting the active silanol groups on the silica surface with specific chemical reagents, thereby enhancing the compatibility and reactive activity of the silica with polymeric matrices. A wide variety of reagents can be employed for such chemical modification, and numerous methods exist; a substantial body of literature and patents addresses these approaches. The following provides a brief overview of some key aspects.

2022-02-19

Challenges Facing the Future Development of the International Rubber Industry

On May 26, the 18th Shanghai Derivatives Market Forum, hosted by the Shanghai Futures Exchange, opened at the Shanghai Futures Building. At the forum’s rubber-themed roundtable held that afternoon, participants engaged in an in-depth discussion on several challenges currently facing the international rubber market.

2022-02-19

The 2021 recovery in global rubber demand is expected to fall short of expectations.

Salvatore Pinizzotto, Secretary-General of the International Rubber Study Group (IRSG), stated that although demand for rubber in Asia, particularly in China, is growing robustly, the recovery of global rubber market demand in 2021 is expected to fall short of expectations, given the potential delay in the large-scale rollout of vaccines.

2022-02-19

Is the day of Black’s rise also the day of rubber’s plunge?

Currently, policy measures are clearly weighing on commodity markets, with black metals showing the most pronounced weakness; prices in this sector have already fallen by more than 20% from their peak. Some individual commodities are beginning to show signs of stabilization.

2022-02-19

Contact phone number:

020-36896519

Company email:

1541901416@qq.com

Huadu Company Address:

1st Floor, Building A2, Zone A, Meiwang Science and Technology Park, Guangzhou Airport Economic Zone (No. 6, Guangtang South Street, Xinya Subdistrict, Huadu District)

Zhaoqing Factory Address:

No. 33-3, Xin’an Avenue, Zhaoqing New District, Dinghu District, Zhaoqing City

Technical Support: Zhongqi Cross-border, Guangzhou

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