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Release paper can be classified in two main ways:
- By the presence of plastic coating: plastic-coated (with plastic) and non-coated (without plastic) release paper.
- By the type of release agent: silicone-based and non-silicone release papers.
1. Plastic-Coated Release Paper
Due to the permeability of release agents, without a proper barrier, the agent may penetrate the paper, leading to incomplete curing and increased usage (and cost) of the release agent. To prevent this, a plastic coating is applied to the paper surface (commonly known as extrusion coating or lamination). In China, polyethylene (PE) pellets are typically used, with a melt index around 7. A common choice is Yanshan Petrochemical’s 1C 7A.
Plastic-coated release papers are divided into:
- Single-side coated (single PE)
- Double-side coated (double PE)
Extrusion-Coated Release Paper is made by coating base paper with PE, then applying release agent to the coated surface. Since the paper surface has fibers and fuzz, the coating must reach a sufficient thickness to prevent penetration, ensuring that the silicone oil does not seep into the paper and avoiding poor release performance. Typically, the coating weight is about 16g/m², but some areas like Wenzhou have achieved 11–13g/m², approaching international standards.
Theoretically, as long as the adhesive can be cleanly removed from the release paper, lower coating weights are acceptable.
Types of extrusion-coated release paper:
- Single-sided PE: Often used for single-sided release paper.
- Double-sided PE: Suitable for double-sided release paper.
For instance, a single-sided release paper might have 20g/m² on the release side and 15g/m² on the back side for better flatness. For double-sided release, both sides might be coated at 22g/m².
Generally, virgin pulp (wood pulp) paper is used—especially in the electronics industry. Using straw pulp paper may cause issues such as fiber shedding and edge breakage during die cutting. Virgin pulp paper types include:
- Natural kraft paper
- White kraft paper
- Yellow kraft paper
- Blue kraft paper
Other base papers include:
- Coated paper
- Art paper
- Duplex board
- Kraft linerboard
- Milk carton board, etc.
As long as the coating adheres well and the film is uniform without penetration, virtually any base paper can be used.
2. Glassine Release Paper
Glassine paper, after supercalendering and coating with release agent, becomes release paper. Due to its high density from calendering, it is well-suited for die-cutting applications.
However, domestic glassine is typically available only in weights between 60–80g/m², whereas many die-cutting factories prefer heavier papers such as 100g/m², 120g/m², or even 140g/m² for better stiffness and die-cutting performance.
Because of this, most base paper must be imported. Yet, imported glassine paper requires a minimum order of 20 tons per container, booked 3 months in advance, and paid in full, making it less attractive to many domestic release coating suppliers.
3. CCK (Clay Coated Kraft) Release Paper
CCK release paper is produced by applying a special clay coating on the surface of kraft base paper, followed by release agent coating. Due to its excellent heat resistance, it is widely used in carbon fiber industries.
However, the clay surface can easily degrade silicone release agents. Therefore, only a few domestic manufacturers can produce CCK release paper with consistently acceptable quality.
4. Other Types of Release Paper
There are also other types of release papers widely used in various industries. Some do not use release agents at all.
For example, label printing companies may apply a layer of varnish as a simple release layer. This can offer limited release properties, but only if the adhesive used is weak—otherwise, it’s ineffective.
Some special-purpose release papers are made using unique adhesive formulations, though they occupy only a small portion of the market.
In the electronics industry, genuine release papers (produced by certified manufacturers with consistent quality and supply) are relatively rare. Most usage relies on "scrap paper"—imported release paper that has been used once or has quality defects.
Adhesive coating factories, however, typically use genuine release paper.