The Role of a Glass Dielectric in Film Treatment

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Glassed Steel Treater Rolls have many characteristics that improve film treatment and product quality:

Dyne (Treatment) Levels
Lower rejection rates and longer shelf life are realized by treating to higher dyne levels. The low power density requirement of a Glassed Steel Treater Roll allows for the highest surface treatment levels, especially important where dyne levels of 50 and higher are required, or when the surface energies of substrates with low surface energies, such as OPP or BOPP, need to be raised substantially.

Faster Treatment (Increased Line Speed)
Glassed Steel Treater Rolls have a power density of 200 sq. inches/KW. This is 25% better than the 250 sq. inches/KW for ceramic and over 50% better than other roll coverings like hypalon, silicone and epoxy. A lower power density requirement will allow an increase in line speed while maintaining current dyne level. When purchasing a new treater station, the lower power density allows the roll and the power supply to be sized smaller, lowering the cost of the treater station. An example of glass vs. ceramic treater rolls is illustrated in the graph below.

Treatment Affected by High Temperatures
Warmer temperatures will cause treat levels to decline and impact product quality when using other roll coverings. Warmer temperatures do not cause these same issues with Glassed Steel Treater Rolls. Glassed Steel Treater Rolls run at cooler temperatures because they dissipate heat better than any other coating. They can also operate in temperatures up to 450°F while still achieving treatment.

Backside Treatment
The Glassed Steel Treater Roll eliminates many of the causes of backside treatment and other treatment related issues:

• Static build-up on the film can cause backside treatment. Thin gauge films, especially, can have a static charge on their surface. The film can actually be pulled from the treater roll surface if the static charge on the web is attracted to the charge on the high voltage electrode. Once pulled from the roller surface, air can become trapped on the underside of the film, causing backside treatment. The glass coating dielectric helps eliminate this problem. The glass surface has a higher opposite charge to the web, which will cause a stronger attraction between the web and the surface of the roll. The result is fewer air gaps and less backside treatment.
  
• The smooth, non-stick surface of glass, which allows the web to spread out tight against the roll (and remove air gaps), also helps eliminate backside treatment. The non-stick surface does not allow dirt or particles to get caught between the web and the roll surface, further reducing the chance of backside treatment.
  
• The lower power requirement of Glassed Steel Treater Rolls also helps eliminate backside treatment. With lower power needed to get the same treatment level, any air gap left between the web and the roll will not have enough power to treat the underside of the web.