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Precautions for the Internal Mold Release Agents in Pultrusion Process

When using internal release agents in the pultrusion process, it’s essential to take certain precautions to ensure the quality of the final product and the safety of the process. Pultrusion involves pulling fibers (typically glass or carbon fiber) through a resin bath and then through a heated die, forming a continuous profile. Internal release agents are added to the resin mixture to facilitate the final product’s release from the mold without sticking. Here are the main considerations based on the provided information:

Chemical Compatibility and Impact

  1. Acidity of Release Agents: Many liquid release agents are acidic and can react with certain materials used in the pultrusion process:
    • Pigments sensitive to acidity may discolor.
    • Alkaline fillers like calcium carbonate can react with acidic release agents, increasing the mixture’s viscosity without affecting the release effect.
    • For fillers like aluminum hydroxide, the release agent can cause moisture release during curing, leading to bubbles and cracks.
  2. Adjusting the Amount of Release Agent: The initial dosage of the release agent should be about 1% of the resin volume, with an effective range of 0.75%-2% based on the resin weight. Adjustments should be made according to the actual situation to avoid issues like delayed curing or excessive resistance during production.

Application and Handling

  1. Safe Handling and Storage: Properly handling and storing the release agent is crucial for preventing accidents and ensuring the quality of the pultrusion process:
    • Wash hands after use.
    • Store in a cool, dry, well-ventilated place, away from high temperatures and direct sunlight.
    • Ensure containers are tightly closed and properly labeled to prevent leaks and contamination.
  2. Personal Protective Equipment (PPE): Operators should wear appropriate personal protective equipment to avoid contact with potentially harmful chemicals in the release agent. This includes protective clothing, gloves, and eye protection, especially when cleaning up spills or handling concentrates.
  3. Environmental Precautionary Measures: Prevent the release agent from leaking into waterways, sewers, or the environment. In case of a significant spill, construct a dike ahead of it for later recovery and disposal.

Product Quality and Performance

  1. Impact on Post-Molding Operations: Over time, the internal release agent may continue to migrate to the surface, potentially affecting coatings and adhesion in post-molding operations. Since the release agent does not always migrate to the mold surface, the use of external release agents is generally not necessary.
  2. Application Techniques: Correct application technique is crucial, especially for carrier-free release agents, as it requires special equipment like electrostatic spray guns. Incorrect use can create dust hazards and require costly equipment investments.
  3. Adjustment Based on Profile Thickness: The amount of release agent varies with the thickness of the pultruded profile. Thinner profiles may require less release agent (e.g., 0.8% or less), while thicker or more complex shapes may need more.

In summary, successful use of internal release agents in the pultrusion process requires careful consideration of chemical interactions, precise dosage adjustments, adherence to safe handling and storage standards, and awareness of the impact on product quality and post-molding operations.

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