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How to Reduce Silicone Migration Issues when using glassine paper

Created on 09.08
Reducing silicone migration when using glassine paper is a common challenge in industries like adhesives, plastics, food, and pharmaceuticals. Silicone migration can contaminate products, hinder adhesion, and cause quality defects.
Here is a comprehensive guide on how to reduce and prevent silicone migration issues.

Understanding the Problem

  • What is Glassine? Glassine is a super-calendered, dense, and smooth paper known for its resistance to air, grease, and water. Its non-stick properties come from a coating of silicone oil.
  • What is Silicone Migration? This is the process where the low-molecular-weight (LMW) components of the silicone coating transfer from the glassine surface to the material it's in contact with (e.g., adhesive, rubber, food, plastic).
  • Why is it a Problem? Silicone is a powerful contaminant. It can:
  • Kill Adhesion: Prevent tapes, labels, and adhesives from sticking.
  • Cause Fish Eyes: Create imperfections in paints, coatings, and plastic films.
  • Contaminate Products: Render food, pharmaceutical, or sensitive electronic components unusable.
  • Inhibit Curing: Interfere with the curing process of certain materials like rubber or sealants.

Strategies to Reduce Silicone Migration

The solution involves selecting the right glassine, handling it correctly, and implementing quality control measures.

1. Choose the Right Glassine Paper (The Most Critical Step)

Not all glassine is created equal. The key is to specify glassine designed for low migration.
  • Specify "Low-Migration" or "Platinum-Cured" Silicone: This is the single most important factor.
  • Traditional Peroxide-Cured Silicone: This older method can leave behind LMW silicone species and breakdown by-products that are highly mobile and prone to migration.
  • Platinum-Catalyzed Addition Cure: This more advanced process creates a much tighter, more cross-linked silicone network. It leaves virtually no LMW residues, drastically reducing the potential for migration. Always insist on platinum-cured silicone-coated glassine.
  • Request a "Cured" Coating: Ensure the silicone coating is fully cured. An under-cured coating will have more free silicone available to migrate. Reputable suppliers will have quality controls to ensure complete curing.
  • Consider Coating Weight: Discuss the silicone coating weight (often measured in grams per square meter, gsm) with your supplier. A very thin coating might not provide a consistent barrier, while an excessively thick one could increase migration risk. An optimal, controlled coating weight is key.
  • Understand the Base Paper: The density and quality of the underlying paper affect how the silicone is anchored. A high-density, smooth base paper provides a better foundation for the coating.

2. Proper Storage and Handling

Environmental factors can accelerate migration.
  • Control Temperature: Store glassine in a cool, climate-controlled environment. High temperatures increase the mobility of silicone molecules, making them much more likely to migrate. Avoid storing near heat sources, in direct sunlight, or in non-air-conditioned warehouses.
  • Avoid Pressure and Friction:
    • Do Not Over-stack pallets or rolls. Excessive weight can force the silicone to transfer, especially in warm conditions.
  • Minimize sliding sheets against each other, as friction can abrade the surface and release silicone particles.
  • Manage Shelf Life: Use older stock first (FIFO - First-In, First-Out). While high-quality glassine has a long shelf life, properties can degrade over extended periods, especially in poor storage conditions.

3. Process and Application Considerations

How you use the glassine also matters.
  • Minimize Contact Time: The longer a sensitive material is in contact with glassine, the higher the chance for migration. If possible, reduce the dwell time. For example, don't store adhesive products in glassine liners longer than necessary.
  • Avoid "Blocking": Blocking is when a material unintentionally adheres to the glassine, and when separated, it can pull silicone from the coating. Using the correct release level (see below) prevents this.
  • Choose the Correct Release Level: Glassine comes in different "release" levels (e.g., easy, medium, tight).
  • Too Easy: Might indicate a looser silicone network, potentially increasing migration.
  • Correct Level: Provides a clean, consistent release without stressing the coating.
  • Too Tight: Can cause fiber tear (pulling paper fibers off) upon release, which is its own contamination problem.
  • Work with your supplier to test and select the ideal release level for your application.

4. Quality Control and Testing

You can't manage what you don't measure.
  • Supplier Qualification: Partner with reputable glassine manufacturers and converters. They should provide certificates of conformity and detailed specifications about their coating process (platinum vs. peroxide).
  • Incoming Inspection: Implement simple QC checks for incoming glassine rolls or sheets.
  • Migration Testing:
  • The "Drawer Test": A common industry practice. Place a sample of the glassine in a closed drawer or container with a sample of your sensitive product (e.g., a piece of adhesive tape or plastic film). Store it at an elevated temperature (e.g., 40-50°C / 104-122°F) for a set period (e.g., 24-72 hours). Afterwards, test the adhesive or material for any loss of tack or performance. This accelerates potential migration.
  • Laboratory Testing: For critical applications, labs can use techniques like FTIR (Fourier-Transform Infrared Spectroscopy) or GC/MS (Gas Chromatography–Mass Spectrometry) to detect and quantify silicone contamination on your product's surface.

Summary: Action Plan

1. Switch to Platinum-Cured Glassine: Immediately contact your supplier and confirm the type of silicone coating. Switch to a platinum-cured, low-migration grade.
2. Audit Your Storage: Ensure your storage area is cool, dry, and out of direct sunlight.
3. Review Handling Practices: Train staff to handle rolls and sheets carefully to avoid abrasion and pressure.
4. Implement QC Testing: Start with the simple "drawer test" to qualify new material batches and periodically check stored inventory.
5. Communicate with Your Supplier: Be specific about your application and your migration concerns. A good technical sales representative can help you select the perfect grade.
By taking a systematic approach—focusing on material selection, storage, handling, and verification—you can effectively eliminate silicone migration as a source of product failure.
Hands handling transparent glassine paper on a green cutting mat.
Ray
Ferrill
Evelyn