Phenyl silicone rubber is a special type of silicone rubber with excellent high-temperature resistance and radiation resistance, widely used in aerospace, atomic energy, and other industries. Its molding process mainly includes compression molding and extrusion molding, each with its specific precautions and technical requirements.

Precautions for Compression Molding Process
1. Raw Material Preparation
Mixing of rubber compound: Phenyl silicone rubber raw gum needs to be uniformly mixed with compounding agents such as fumed silica and diphenylsilanediol in an open mill or internal mixer. The mixing temperature should be controlled below 40℃ to prevent scorching or volatilization loss of the vulcanizing agent.
Vulcanizing agent selection: For phenyl silicone rubber molding, the use of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) (Bis-25) vulcanizing agent is recommended, with a vulcanization temperature typically of 170℃.
Rubber compound storage: After mixing, the rubber compound needs to be stored for at least 24 hours to allow the compounding agents to fully react with the raw rubber.  Remixing is required before use.

2. Mold Preparation
Mold cleaning: Wipe the mold cavity and parting surface with alcohol or a special cleaning agent to remove residual rubber and oil stains.
Mold preheating: After installation on the vulcanizing machine, preheat to the vulcanization temperature (usually 150-180℃). Preheating time is 10-20 minutes.
Release agent application: For complex cavities, spray a small amount of neutral release agent (such as silicone oil), a thin layer is sufficient.

3. Key Parameters for Compression Molding
Vulcanization temperature: 150-180℃ (high-hardness silicone requires 170-180℃, low-hardness 150-160℃)
Vulcanization pressure: 5-20MPa (small products 5-10MPa, large products 10-20MPa)
Vulcanization time: Approximately 40 minutes
Extrusion Molding Process Precautions
1. Mixing and Remixing
Special equipment: It is best to use a silicone rubber-specific open mill, maintaining a clean environment.
Temperature control: The open mill rollers should be cooled with water to prevent scorching of the rubber compound.
Remixing requirements: After mixing, the rubber compound must be remixed after 24 hours of storage. Remixing is done using an open mill with a roller gap of 3-5mm.
2. Extrusion Operation Key Points
Extruder selection: Use a hollow screw design that allows for water cooling; temperature control is very important.
Common problems:
Bubbles: Vulcanization temperature is too high or the mixed rubber compound has high moisture content.
Product deformation: Increase the high-temperature vulcanization oven (600-800℃) or use a vertical extruder with a high-temperature section oven.
Product blooming: Add AD to the mixed rubber compound. 904 Additive
3. Process Parameters
Temperature Control: Feeding section 130-150℃, Compression section 150-180℃, Metering section 170-200℃
Screw Design: Gradual screw with low compression ratio (1.5-2.5:1) and high length-to-diameter ratio (L/D=20-25:1)
Draw Ratio: 1.2-3.0, too high can easily lead to wire breakage, too low results in a rough surface
Comparison of Two Processes
Process Parameters | Compression Molding | Extrusion Molding
Applicable Products | Complex shaped products | Continuous profiles (pipes, rods, bars, etc.)
Vulcanization Temperature | 150-180℃ | Segmented temperature control (130-200℃)
Pressure Requirements | 5-20MPa | Extrusion pressure control
Production Efficiency | Single piece production | Continuous production
Equipment Investment | Vulcanizing machine | Extruder + auxiliary equipment

Common Problem Solutions
Bubbles in molded products:
Apply pressure slowly during vulcanization, vent 2-3 times after mold closure
Check if the mold vent grooves are clear (depth 0.03-0.05mm)
Deformation of extruded products:

Add a high-temperature vulcanization oven (600-800℃) between the extruder and the drying tunnel
Increase the green strength of the compound (add AD 904 additive)
Surface defects of products:

Molding: Check the cleanliness of the mold, ensuring no impurities
Extrusion: Adjust the streamlined design of the die head to reduce melt stagnation dead zones
By strictly controlling the above process parameters and precautions, the quality and performance of phenyl silicone rubber products can be ensured to meet the requirements of special application fields. In actual production, it is recommended to optimize and adjust the process parameters according to the specific product characteristics and production conditions.