When most people think about pressure-sensitive adhesive tape, rolls of tape spring to mind. Yet pressure-sensitive tapes are also supplied in other formats. Tape converters provide a significant service by converting rolls of tape into various shapes and forms designed to provide functionality, ease of application and other benefits to the user.It’s important to be aware of some of the challenges that converters face when processing pressure-sensitive tapes and some special tape features which can make converting easier. If you’ve ever tried converting pressure-sensitive tapes, you know that the process has the potential of leaving you raising an eyebrow in confusion.
Pressure-sensitive tapes are available in countless adhesive types and constructions, each of which has different properties. The converter must figure out how to satisfy the customer by processing the tape for the needed use while juggling all these variables.
Pressure-sensitive tapes are constructed using:
- Carrier or Backing
- Release Liner
Additionally, these tapes are categorized into four basic types:
- Single Side Coated
- Double Coated
- Transfer Adhesive
Let’s talk about adhesives first. Popular adhesive types are rubber, acrylic, silicone and urethane. Adhesives can be soft or firm, thick and heavy or thin and light, permanent or removable and high tack or low tack. If you thought that was a lot of options, carriers and backing types are almost endless! Backing materials often appear as films, fabrics, non-woven materials, fiberglass, metal foils or foam. Release liners, on the other hand, are usually made of paper or film, though other materials can also be used.
Now let’s move on to tackling converting! This process can be simplified by considering a few principles:
Firmer adhesives tend to be easier to cut. The firm adhesive reduces the chance for edge smear, but firm adhesives don’t flow easily and can be difficult to laminate or bond to soft porous materials, such as foam. Firm adhesives usually work well for laminating smooth, high-surface energy films, like polyester. A thinner adhesive coating also helps the cutting process by reducing the chance of adhesive smear and providing a cleaner edge.
Softer, higher tack adhesives are generally more difficult to cut. These adhesives move or flow when cut, thereby increasing the chance for adhesive to ooze and smear on the part edges or cutting blades. The good thing about softer, tackier adhesive is the flow properties which make it difficult to cut actually help when laminating to soft or rough surfaces, like foam. Adhesives used for bonding to low- energy films or surfaces are generally soft and tacky, too. Frequently, glass fibers or other fillers are added to soft adhesives to provide them with a little body, thereby reducing the adhesive flow and subsequent adhesive smear problem.
Removable adhesives are generally fairly simple to cut because the coating is almost always very thin. In addition, the adhesive has removable properties and doesn’t have a strong bond to parts or materials.
The most common release liners are paper. Still, it’s important to keep in mind there are different paper liners, and they all cut differently. The liner thickness is also a factor when die cutting, slitting or laminating. The most popular paper liner is densified kraft. Densified kraft liners are hard and dense, which helps provide a nice clean cut during die cutting or slitting. Thicker densified kraft liners aid with kiss cutting applications as well. It’s easier to control the cut depth and prevent cutting through this type of liner.
Poly-coated paper release liners provide better lay flat properties and are often preferred for flatbed die cutting operations or sheet laminating applications. Two great features of poly-coated release liner are that it doesn’t absorb moisture easily, and cut parts tend to maintain their shape better and longer when using this liner. Poly-coated paper liners have a thin polyethylene coating, which produces a soft surface. Sometimes the die blade won’t cut cleanly through a soft surface, leading to poorly cut parts or defects.
Meanwhile, clay-coated paper liners have some properties of the poly-coated liner and some of the densified kraft liner. Clay liners help protect from moisture but not as well as poly-coated ones. They’re also a little harder than poly-coated liners but not as hard as a densified kraft liner.
While other paper liners exist on the market, these are the most popular kinds for tapes.
There are other paper liners but these are the most popular for tapes.
Film release liners are often incredibly helpful in getting the job done. The most popular film liners are polyester and polyethylene. These have great moisture resistance and are excellent for long-term use. They die cut and slit well, are more durable than paper liners and provide a smoother, higher quality adhesive surface. The flexibility of film liners also travels over rollers and through machinery more seamlessly to prevent other problems.
Carriers and Backings
Foil materials can be difficult to cut because the edges of the foil tend to fold over or deform. This can be mitigated with the use of a lay-down roll to flatten the edges. Thinner and firmer adhesive and liner can also be helpful. Yet thick materials like fiberglass cloth and fabrics will compress during die cutting. Keep in mind sharp blades help produce a clean cut out of these types of materials.
Foams come in all sorts of thicknesses. They are usually more of a challenge to laminate then cut but, as is the case with fabrics, compressing foams and using sharp blades on them can help produce a quality cut. When laminating foam, problems such as liner pop off or creasing can occur as material moves over rollers and through the lamination process. To help when laminating soft materials like foam, try using a tape that has a tighter release value. Tighter liners are less likely to separate from the adhesive layer, avoiding the pop off phenomenon. Using a film release liner is also effective in reducing foam lamination problems. Flexible film liners allow the tape to travel over sharp bends and through converting processes more easily, thus reducing the chance of creasing or pop off.
So, the next time you have trouble converting adhesive tapes, ask your supplier if these or other tape features will provide the solution you need. For more information on adhesive tape converting, visit the links below.