Electrical connectors need to do more than establish a reliable connection. They must also withstand heat, mechanical stress, and potential electrical failures without compromising safety.
For connectors used in household appliances and other electrical equipment, glow-wire resistance is an important consideration during material selection. Meeting these requirements, however, can create challenges for manufacturers, particularly when flame retardancy comes at the expense of mechanical toughness.
Asahi Kasei is developing a new LEONA™ High Glow-Wire Flame-Retardant PA66 grade designed to address both challenges.
Glow-wire testing evaluates how plastic materials and finished components respond to contact with a heated metallic element. It is designed to simulate conditions that may occur when electrical components overheat.
Two common material-level measurements are used to evaluate glow-wire performance:
These measurements are defined under IEC 60695-2-12 and IEC 60695-2-13, respectively.
For connector manufacturers, understanding these properties is an important part of identifying materials suitable for applications with demanding electrical safety requirements.
IEC 60335-1 establishes general safety requirements for household and similar electrical appliances, including requirements associated with components that support current-carrying connections.
For certain unattended connections carrying more than 0.2 A, the applicable glow-wire requirements can be particularly demanding.
Relevant material-level criteria include:
Materials meeting applicable criteria may help simplify the evaluation process for finished components under IEC 60335-1.
However, material performance alone does not guarantee that a finished connector will pass end-product testing. Connector geometry, material thickness, and actual operating conditions must also be considered.
Achieving high glow-wire resistance is only part of the equation.
Electrical connectors often incorporate snap-fit connections, locking tabs, and other features that experience mechanical stress during assembly and use.
Conventional high glow-wire flame-retardant materials may require substantial flame-retardant loading to achieve the desired performance. Unfortunately, this can reduce toughness and increase the likelihood of cracking when components are subjected to deformation.
For manufacturers, the challenge is finding a material that delivers both flame-retardant performance and the mechanical properties required for the application.
A connector that meets its fire safety requirements but cracks during assembly is not an effective solution.
To help address this challenge, Asahi Kasei is developing a new LEONA™ PA66 grade that combines high glow-wire resistance with improved mechanical toughness.
Internal testing of the development grade has demonstrated several promising properties:
One particularly important advantage is the material's performance in snap-fit applications.
In comparative testing, the LEONA development grade demonstrated a tensile strain at break of 5.0%, compared with 1.2% and 2.7% for two conventional high glow-wire flame-retardant materials.
The material also passed an internal snap-fit evaluation without cracking, highlighting its potential for connector designs incorporating locking and retention features.
These results reflect internal development testing. Equivalent ratings do not represent third-party certification or registration, and material properties may change as development continues.
Beyond glow-wire resistance and toughness, electrical tracking resistance can influence connector design.
Comparative Tracking Index (CTI) measures a material's resistance to electrical tracking across its surface.
Materials with higher CTI values may allow engineers to reduce creepage distances while maintaining the requirements associated with a given voltage and environmental condition.
The new LEONA development grade has demonstrated CTI 600V-equivalent performance, placing it in Material Group I under the relevant IEC classification.
This may provide opportunities for more compact connector designs, reduced terminal spacing, or additional electrical connections within a given footprint.
Final dimensions must always be evaluated against applicable standards, pollution degree, voltage, and end-product requirements.
The combination of glow-wire resistance, mechanical toughness, and tracking resistance makes this LEONA development grade particularly interesting for appliance connectors and other electrical components with demanding performance requirements.
Potential applications include connectors for refrigerators, air conditioners, and other household appliances.
The material is still under development, and Asahi Kasei Plastics North America is looking for manufacturers interested in evaluating its potential.
If you're working on a connector application that could benefit from these properties, we'd like to hear from you.
Samples may be available for evaluation. Simply contact our team to discuss your application and learn more about the material.
If you're looking for expert guidance on selecting durable, high-performance connector materials, our team is available to help. Contact us today to learn more about how our engineered plastics can power your next project.