Making the right choice when selecting a composite for electrical or mechanical use is critical because it directly affects performance and reliability. GPO-3, an electrical and mechanical composite with strong insulating characteristics and mechanically robust performance, is one of the most commonly used materials in a variety of electrical and mechanical applications. From electrical cabinets to switchgear to industrial equipment, designers, engineers, and procurement specialists must become familiar with GPO-3 and how it compares to other established materials such as FR4.
In this article, we will provide a detailed overview of GPO-3’s important characteristics, as well as its key applications and relevant comparisons to FR4, an essential material in the electronics and insulation industries. By the end of this article, you should be able to identify where GPO-3 outperforms and why it is increasingly used in modern electrical applications.
What Is GPO-3?
GPO-3 is a composite made from fiberglass mat reinforced with unsaturated polyester resin and embedded in polyester resin to form a homogeneous composite that exhibits mechanical and electrical properties consistently throughout the part. This allows GPO-3 to be effectively used as an electrical insulating material that provides consistent performance regardless of the environmental conditions in which it is used. The fiber orientation of the glass mat used in GPO-3 is randomized rather than woven, making it an isotropic material (having the same properties in every direction).
ELECTRICAL PERFORMANCE
One of the most important characteristics of GPO-3 as an electrical insulation material is its dielectric strength and tracking resistance in medium-voltage service.
In addition, GPO-3 generally meets UL94 V-0 flammability criteria and is highly flame resistant, which is a safety feature when using GPO-3 in electrical applications.
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ELECTRICAL INSULATION
GPO-3 has excellent dielectric properties, enabling it to operate successfully in very high electric fields. As a result of these dielectric properties, GPO-3 is used extensively in switchgear and busbar support applications where insulation integrity and arc resistance are essential.
GPO-3 has a CTI of over 600 volts, demonstrating that it provides excellent resistance to surface tracking and arc tracking/electrical discharge, making it ideal for applications requiring high safety levels.
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MECHANICAL PROPERTIES / STRENGTH AND STABILITY
Although the mechanical strength of GPO-3 is less than that of other materials, such as FR4, it still has good compressive and impact resistance, making it suitable for providing structural insulation properties, both electrical and mechanical.
GPO-3 is homogeneous in structure, allowing it to maintain good edge definition during the machining of precision-molded parts by manufacturers.
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THERMAL / ENVIRONMENTAL PROPERTIES
GPO-3 has a high degree of heat resistance, as it can typically operate continuously at around 155 degrees C and, depending upon the unique grade, may also operate continuously at a higher temperature. The thermal properties of GPO-3 make it an excellent insulation material in high-temperature conditions.
While GPO-3 is more moisture-resistant and chemically resistant than PC-1, it has lower moisture resistance than FR4. This is due to the natural properties found in polyester resin.
GPO-3 has excellent dielectric strength as well as good arc resistance, making this composite suitable for use as insulation in electrical cabinets, busbar supports, transformer barriers and panels, and partitions in switchgear applications. These types of applications require materials that can hold up under electrical stress without breaking down.
GPO-3 is also frequently used in the medium-voltage electrical industry to provide reliable insulation between electrical cabinets and bus supports, phase separators, and protective barriers. The ability of GPO-3 to provide an insulating barrier between electrical components, due to its ability to withstand arc stress, continues to promote safety and reliability throughout the power distribution equipment industry.
Because of the mechanical strength and machinability of GPO-3, it is also an ideal material for structural parts such as spacers, machine components, and safety covers for many industrial applications.
FR4 – What Is It?
FR4 is a fiberglass-reinforced epoxy laminate and has been used as the standard substrate material in the electronics industry for many years. The product is created by impregnating woven fiberglass cloth with a highly durable epoxy resin binder. The epoxy resin is cured into a structural, flame-resistant laminate.
The term “FR4” means “flame-resistant” and refers to the self-extinguishing characteristics of the material. The material also meets the requirements for UL94 when evaluated.
Core Properties
FR4’s mechanical strength, high dielectric characteristics, and low water absorption make it an ideal material for printed circuit boards and components that require high-precision insulation.
The stable behavior of FR4 in humid and dry environments and its high-impact resistance continue to provide reliability and high performance for many manufacturing industries, including consumer electronics, automotive assemblies, and other high-stress applications.
Comparing GPO-3 to FR4
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Electrical Performance
GPO-3 has much greater arc and tracking resistance, making it the right material for use in high-arc applications, such as busbars and switch support components.
FR4 has a greater physical capacity to handle heavier loads than GPO-3. This is due to the fact that FR4 has a more structured mechanical composition than GPO-3. Therefore, FR4 provides enhanced structural support for use in transmission systems such as busbars that are standardized across regional systems through market standards.
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Moisture & Temperature Resistance
FR4 has a lower rate of water absorption than GPO-3, which helps preserve its electrical value when utilized in wet environments. GPO-3 has strong electrical resistance and generally has higher water absorption levels than FR4 due to the hydrophilic nature of the polyester resin used in its manufacturing process.
Both materials perform well up to Class F insulation standards when exposed to heat. FR4 can have added resistance for Class H thermal applications, where it performs well.
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Cost and Machinability
Given the simple manufacturing process used to create GPO-3, the material is generally more cost-efficient for engineers to use when designing large insulation barriers or manufacturing electrical boards. GPO-3 may provide strong performance at a lower cost than FR4; however, FR4’s greater mechanical strength and more widespread acceptance within the engineering community provide demonstrable value when designing CNC-machined components using FR4 materials.
GPO-3 is a good choice for high-arc electrical insulation, panel barriers, busbar supports, or medium-voltage electrical circuit boards, whereas FR4 may be more cost-effective for higher-rated electrical applications and components. For applications that require precision-machined parts or electrical substrates that offer mechanical integrity and moisture resistance, the best material choice available in North America is generally FR4.
What You Should Consider When Selecting Materials
Before selecting the final material for your product, you must evaluate the operating conditions expected for your application. While GPO-3 may have adequate arc resistance, FR4 ultimately has greater mechanical stability and dielectric properties over time.
If your application has a large required insulation area, then GPO-3 may have a better unit cost. However, given that FR4 is a highly popular material, it is readily available in the marketplace and more standardized than GPO-3, making it easier to source.
Frequently Asked Questions About GPO-3 and FR4
What are the main uses of GPO-3?
For use in electrical insulation applications such as switchgear, transformers, and busbar supports, and other types of electrical applications requiring electrical insulation performance, as well as good arc and dielectric performance.
Is GPO-3 better than FR4?
No. While GPO-3 provides excellent arc and high tracking resistance, FR4 offers greater mechanical strength and lower moisture absorption than GPO-3.
Can GPO-3 be machined as well as FR4?
Yes. However, because FR4 is a woven material, it provides better accuracy for machined mechanical parts compared to GPO-3.
Will GPO-3 withstand high temperatures?
Yes, GPO-3 can withstand high temperatures, generally up to Class F limits, similar to many types of FR4 material.
What do I need to consider to select the best material for my application?
You must evaluate all relevant electrical, mechanical (strength), environmental, and cost factors to determine the optimal material choice for your application.
Summary: Which One is Better?
Both GPO-3 and FR4 are effective materials for use in electrical insulation and laminate composites. GPO-3 is a well-suited choice when arc resistance is required and when low-cost insulation is needed. In addition, GPO-3 provides good tracking resistance, while FR4 has strong mechanical strength and low moisture absorption, and is commonly used in the electronics industry.
Both GPO-3 and FR4 have proven their utility in industrial design and electrical applications, regardless of whether you are specifying insulation barriers or selecting materials for high-precision components.
WM F McGraw is a leading source of material technical expertise and material supply resources in North America. We provide engineers and manufacturers with information and tools to enable them to make informed choices when evaluating materials according to required properties, costs, and applications. The company has a strong commitment to supporting engineers and manufacturers in developing a comprehensive understanding of how to use engineering materials effectively.
