The Language of Plastics Welding

Brittany PullenContract Manufacturing

What comes to mind when you hear plastics welding? Might it be a masked welder with a hot torch? For those not familiar with the art of radio frequency (RF) welding that may be the exact image that comes to mind. Yes, plastics welding involves heat but not in the same manner as metal welding. To dive deeper into the process of plastics welding visit our recent blog Radio Frequency (RF) Welding 101, where we explain each step in the welding process and discuss why manufacturing with RF welding is a great option for many industries looking into getting a plastic welder on site.

The Language of Plastics Welding

Today let’s unwrap the terminology and language of plastics welding. By better understanding some of the terms associated with the process, those exploring plastics welding as a supply chain solution can be better equipped to make impactful decisions.

Radio Frequency (RF Waves): High frequency electromagnetic energy (usually 27.12 MHz) similar to a microwave but heating plastic instead of warming up leftovers.

RF Heat Sealing: High frequency power applied to two or more layers of thermoplastic material to create a seal or bond in the shape of a die.

Bipolar Molecules or Dipoles: Molecules with one end positively charged with respect to the other end.

Polar Plastics: Plastic material that have molecules with one end positive and the other end negative. In other words, polar plastic material contain a dipole molecules and two atoms are oppositely charge creating a net difference of charge in the bond.

Non-Polar Plastics: Plastic material with molecules that do not have one end positive and the other end negative. In other words, non-polar plastics do not have enough difference in net charge to react to RF welding.

Thermoplastic: Plastic polymers that become soft and moldable upon heating and return to their original hardness and strength upon cooling and this process can be repeated. This is contrary to thermoset, which when melted will not return to its original form.

Seal: A fused point between plastic material that creates a liquid or air tight joint that otherwise would not be.

Weld Width: The width of the actual RF welded seam.

Bond vs Weld (Chemical vs Mechanical): In RF heat sealing, when two like materials are welded they become fused and become one with each other in the welded area. When materials are bonded only they are mechanically held together, such as bonding with an adhesive in between, using something like this shrinkfast 998 shrink wrap gun. They are still two separate materials and a bond is weaker than that of a true RF heat sealed weld.

Machine Direction vs Transverse Direction: Machine Direction -The direction parallel to the machine as the film moves through the machine. Transverse Direction -The direction perpendicular to the machine as the film moves through the machine.

Material Shrink: Decrease in dimension of a film when subjected to heat.

Sided Material: Having two different chemical compositions of material on either side of the film.

Layered Material: Having multiple chemical compositions of film in one material.

Carbon: When a flash or an arc occurs in the welding process it can leave the chemical element carbon as the exposed materials burn.

Arcing: An electrical arc or flash that can occur during the welding process causing damage to the materials and/or the tooling and needs to be repaired before the process can continue.

Plastics welding or RF heat sealing is often utilized for medical device manufacturing for items such as fluid bags, infection control devices and patient warming products. It also is utilized for heat sealed military applications such as hydration pouches, safety products and protection gear. Most often polar materials such as polyvinylchloride (PVC) and polyurethane (PU) are utilized in the RF welding process. However, due to our diverse heat sealing solutions, from radio frequency to impulse to ultrasonic welding, clients can consider non-polar materials as well, such as olefins, TPEs and bio-derived plastics.

View products manufactured utilizing Radio frequency welding process.