Low Dielectric Constant Plastic Materials
TOPAS cyclic olefin copolymer has electrical properties, such as low dielectric constant (low permittivity), matched only by fluoropolymers and certain low temperature plastics. This makes TOPAS COC an attractive material for electronic components such as antennas, and in other high frequency or low permittivity applications. COC can be used alone, or blended with olefin plastics like polyethylene and polypropylene to raise the heat resistance of these cost-effective resins in such applications.
What Is TOPAS COC?
COC is an acronym for Cyclic Olefin Copolymer. These high-performance thermoplastic, amorphous polymers are created by combining a cyclic olefin monomer known as norbornene, with the standard plastic building block ethylene. In their natural state, COC plastics are rigid and glass-clear. At TOPAS Advanced Polymers, we manufacture a broad lineup of COC grades with heat resistance ranging from room temperature to 170C (338F). In addition to electronic products, TOPAS COC is widely used for its unique performance benefits in food, medical, and general-purpose packaging, medical devices and containers, diagnostic devices and disposables, and optical componentry including modern touchscreen layers.
TOPAS COC enables miniaturization of components. With amfantastic azing detail reproduction at even submicron scale, high flow for complex geometries, and high dimensional stability, it's become the clear choice for the compact, lightweight products of tomorrow.
Electronics environments can be challenging to ordinary plastics. Beyond heat resistance, chemical exposure is a potential threat. TOPAS COC is resistant and serves as a barrier to chemicals as varied as alcohols, DMSO, acetone, acids, bases, and more. These and other polar materials can wreak havoc with many common plastics. This makes TOPAS COC the best solution for many applications where chemical exposure is a risk. TOPAS resins are also moisture insensitive and provide an excellent moisture barrier.
TOPAS COC is an incredibly pure polymer. Leachables and extractables are extremely low, as evidenced by the everyday use of COC in high purity medical applications where medical glass and other plastics fail. Because offgassing can be an issue in electronics manufacturing, why not start with as pure a material as possible?
What is Dielectric Constant?
Dielectric constant is an electrical property of plastic - or any material. It can be defined as the ratio of the change stored in an insulating material placed between two metallic plates to the charge that can be stored when the insulating material is replaced by a vacuum or air. Dielectric constant is also referred to as permittivity, electric permittivity, and sometimes relative permittivity as it relates to the permittivity of free space.
How to Calculate Dielectric Constant
The dielectric constant is commonly defined as the ratio of the capacitance induced by two metallic plates with an insulator between them to the capacitance of the same plates with a vacuum between them.
An insulating material with a higher dielectric constant is needed in electrical and electronic applications where a high capacitance ratio is necessary.
When using a material specifically for insulating purposes, that material should have a lower dielectric constant in order to achieve desired results.
The dielectric constant formula is: κ = C / C0
If C is the value of the capacitance of a capacitor filled with a given dielectric and C0 is the capacitance of an identical capacitor in a vacuum, the dielectric constant, symbolized by the Greek letter kappa, κ, is simply expressed as κ = C/C0. Reference: britannica.com (https://www.britannica.com/science/dielectric-constant)
Applications of Dielectric Constant
- Materials in the production of capacitors that are commonly used in radios and other electrical equipment
- Commonly used by circuit designers to compare different printed circuit board (PCB) materials
- Used in the development of materials for energy storage applications
- Antennas for 5G, 6G and other applications in modern telecom
Polymer-based dielectric composites are desirable for applications ranging from electronic packaging, to embedded capacitors, to energy storage. These composites are highly flexible with low process temperature, and they exhibit a relatively high dielectric constant, low dielectric loss, and high dielectric strength.
Polar and Nonpolar Plastic Characteristics
The dielectric properties of a polymer are typically dependent on its specific structure. The structure is what determines whether a polymer is polar or nonpolar. And whether a structure is polar or nonpolar determines the electrical properties of the polymer.
In polar polymers (PMMA, PVC, high-density polyethylene, Nylon, PC, etc.), dipoles are created due to an imbalance in the distribution of electrons. These dipoles tend to align in the presence of an electric field. Hence, this creates dipole polarization of the material, making these materials only moderately suitable as insulators.
While non-polar polymers (PTFE, PP, PE, PS) have symmetrical molecules and are truly covalent, there are no polar dipoles present in them, and hence the presence of an electric field does not align the dipoles. However, slight electron polarization occurs due to the movement of electrons in the direction of the electric field, which is effectively instantaneous. These polymers have high resistivities and low dielectric constant.
Polar plastics are much more likely to absorb moisture from the atmosphere. The presence of moisture also raises the dielectric constant, which in turn lowers the resistivity. When the temperature increases, there is a faster movement of polymer chains and a more rapid alignment of dipoles. This invariably raises the dielectric constant values for polar plastics.
Non-polar plastics, on the other hand, are not affected by moisture or relative increases in temperature. Note that COC is a non-polar polymer.
Dielectric Constant Values for Several Polymers:
- Cyclic olefin copolymer (TOPAS® COC), 2.2
- Polytetrafluoroethylene (PTFE), 2.1
- Polypropylene (PP), 2.2
- Polyethylene (PE), 2.2
- Polystyrene (PS), 2.5
- Polyethylene terephthalate (PET), 3.0
- Polyvinyl chloride, PVC, 3.2
Consistent Properties for Reliable Performance
Many polymers are sensitive to moisture, meaning that when humidity changes, films and components may suffer subtle shifts in dimensional, electronic, and dielectric properties. TOPAS cycloolefin polymer is unaffected by moisture, and because most grades are 100% amorphous, dimensional accuracy is not affected by crystallization as many plastics can be. Blends of semicrystalline resins (PP, PE) with COC are more dimensionally stable in processing. When precise and consistent performance is essential, TOPAS COC is the safe choice for tight tolerances and stable electronic properties.
The most common thermoplastic resin processing techniques are suitable for TOPAS cyclic olefin polymers. Injection molding, and cast and blown film extrusion are all widely utilized. Solvent casting is also possible. Flexible or soft items can be made from TOPAS Elastomer E-140, an elastomeric grade of COC with high purity that can be injection molded, overmolded or extruded into films.