Dielectric Material

What does dielectric mean?

In the context of high-frequency (HF) welding, dielectric refers to a material’s ability to transmit electric force without conduction. In HF welding, the material being welded is subjected to an alternating electric field. The dielectric properties of the material determine its ability to respond to this field, leading to heat generation and ultimately fusion between the materials being joined. Materials with higher dielectric properties, such as PVC and PU, are commonly used in HF welding applications due to their ability to generate heat efficiently under the influence of an electric field.

What does non dielectric mean?

“Non-dielectric” typically refers to materials that do not exhibit significant dielectric properties. Unlike dielectric materials, which can efficiently generate heat when subjected to an alternating electric field, non-dielectric materials do not respond strongly to such fields and thus do not generate heat through dielectric heating. Instead, non-dielectric materials may rely on other mechanisms, such as direct heating or the use of adhesives, to achieve fusion or bonding during welding processes. Examples of non-dielectric materials include metals and certain types of plastics, which are typically poor dielectrics and require alternative welding methods such as resistance welding or laser welding.

What are some materials that are dielectric?

  • PVC (Polyvinyl chloride): Widely used in various industries for its flexibility, durability, and dielectric properties.
  • PU (Polyurethane): Another common material known for its flexibility and dielectric properties, often used in applications where flexibility and resistance to abrasion are required.
  • TPU (Thermoplastic polyurethane): Similar to PU but with enhanced properties, TPU is often used in applications requiring high elasticity and durability.
  • PET (Polyethylene terephthalate): Used in a variety of applications including packaging, textiles, and electrical insulation due to its dielectric strength.
  • EVA (Ethylene-vinyl acetate): Known for its flexibility, toughness, and dielectric properties, EVA is often used in products such as footwear, packaging, and solar cell encapsulation.

These materials have the ability to generate heat efficiently when subjected to an alternating electric field, making them suitable for welding processes that rely on dielectric heating.

What are some methods for welding dielectric materials?

For welding dielectric materials such as PVC and PU, high-frequency (HF) welding is the primary method used due to its effectiveness in generating heat within the material. However, there are also alternative methods for welding dielectric materials, though they may not be as commonly employed. Some of these methods include:

  • High Frequency Welding: (Best method) High Frequency (HF) or Radio Frequency (RF) welding is a method of joining thermoplastic materials using radio waves and pressure to create high-quality welds. This process, operating at 27.12 MHz, involves the application of electromagnetic energy to the surfaces to be joined, generating heat within the material itself.
  • Hot Air Welding: This method involves using heated air to soften the surfaces of the materials being welded, followed by pressing them together to create a bond.
  • Ultrasonic Welding: Ultrasonic is sound that accelerates down into a ”Sonotrode” (tool) resulting in a mechanical hammering effect. This pounding generates heat in most fabrics. The heat needs to penetrate the first layer in order to join the second layer.
  • Impulse Welding: Impulse is a technology where a steel band is covered with PTFE tape and where electrical current is running through the steel band.
  • Hot Wedge Welding: The hot wedge is a process where the material is dragged against a hot surface (wedge) and where rollers press the preheated surfaces together.