The Use of Heat-Shrink Tunnels in the Packaging Industry
Shrink tunnels are used in a variety of industries for retail, food, and industrial packaging. Chances are, you’ve already unwrapped a number of boxes this week from any given market that have been neatly packaged with the help of shrink-wrap. The impact and scope of this packaging practice is immense and almost limitless.
Food packaging alone is a massive industry consisting of thousands of machines, products, and supplies. Companies spend millions of dollars annually to improve and perfect food packaging that can increase shelf life and enhance brand appeal. Shrink-wrapping is used in the largest conglomerates all the way down the line to smaller, regional commercial kitchens and bakeries.
Think about the countless industries that use that shrink-wrap packaging and rely on shrink tunnels as part of this process: games and sporting goods, printing and paper products, hardware and housewares, electronics, pharmaceutical companies … the list is endless.
The Heat-Shrink Process
A shrink tunnel is equipment that uses a chamber to produce heat with a continuous conveyor running through it. Heat-shrink packaging tunnels convey products that are encapsulated with poly film through a heated tunnel/oven; the heat causes the poly film to shrink and form easily around the products.
Another common component of a heat-shrink packaging tunnel is an L-bar sealer. An L-bar sealer has a sealing surface that is in the shape of a backwards “L.” The L-bar sealer heat seals the poly film by the heated L-shaped arm prior to conveying through the heat-shrink tunnel. It is often preferred over an impulse sealer for fast sealing times.
Advantages of Using PTFE-Coated Fiberglass in Heat-Shrink Tunnel Equipment
Manufacturers of heat-shrink tunnels design this equipment to use a variety of PTFE-coated fiberglass and silicone-coated fiberglass products because of the advantages discussed below.
- Facilitates Airflow
PTFE-coated open mesh belts are typically fabricated to convey product through the heat-shrink tunnel. The openings within this type of belt allow exceptional airflow so that the product is heated evenly. These open mesh belts come with sewn and sealed edges for added re-enforcement, along with metal alligator splicing that join both ends of the belt together. There is an option to have the splice covered with a PTFE-coated fiberglass fabric so that product will not stick to the metal alligator splice. The PTFE-coated fiberglass fabric is called a “cover flap.” This is not mandatory, but a preference.
The principle behind this type of belt is to protect the film and product from marking or become damaged during the heat-shrink process, which guarantees a cleanly packaged finished product.
- Non-stick properties
PTFE-coated fiberglass tapes are often applied on the L-bar sealer on top of the silicone or sponge rubber. The combination of the PTFE-coated fiberglass tape and silicone rubber allows for the L-bar to properly heat seal the poly film around the product without the poly film sticking to the heating element.
- Prevents excessive heat loss
Additionally, there are strips of silicone-coated fiberglass that act as a curtain at the beginning and end of the heat-shrink tunnel. The silicone-coated fiberglass fabric “curtain” prevents excessive heat loss at the entry and exit of the tunnel/oven. The non-stick properties of the silicone-coated fiberglass fabric resist adhesion of any melted poly film
Apart from that, PTFE-open mesh belts, PTFE tapes, and silicone fabrics also have an extensive operating temperature range from -100°F (-73°C) to +500°F (260°C).
Based on years of experience, and sampling many products, we can offer market recommendations for what suits your needs for which application. Our fabrics are made from woven fiberglass cloth with a clear PTFE coating. These plastic-coated fabrics are non-toxic, odorless, tasteless, and are FDA compliant (21 CFR 177.1550).
Contact us to obtain samples for your evaluation today!