Plastics for Electrical and Lighting applications require a very specific combination of properties. Primary material considerations include: flammability, electrical, thermal, mechanical, and weatherability.
Electrical applications are highly regulated needing to meet or exceed several international industry standards such as IEC, ISO, EN, and UL. End use devices are tested to application specific standards to ensure compliance with these standards. While plastics are not subjected to all the testing a device will see, plastics can be characterized by a few major test standards. These common UL standards and are outlined to the right. The primary test standards include: UL94 Flammability, UL746A Comparative Tracking Index (CTI), UL746B Relative Thermal Index (RTI), and UL746C Weatherability. Plastics used in electrical devices are also subject to constantly evolving sustainability regulations including RoHS and WEEE. Conventus offers solutions that meet the latest directives.
Conventus offers FR solutions for most engineering and high performance polymers used in Electrical / Lighting applications such as ABS, PC/ABS, PC, PBT, PPE, PA66, SPS, PPA, PPS, PSU, PES, PPSU, & PEEK. OEMs enjoy access to over 300 products with UL yellow cards when working with Conventus.
The temperature below which is a class of critical property will not be unacceptably compromised through chemical thermal degradation, over the reasonable life of an electrical product is defined as the Relative Thermal Index ( RTI).
Electrical RTI, associated with critical insulating properties
Mechanical Impact RTI, associated with critical impact resistance, toughness, elongation and flexibility properties.
Mechanical strength ( Mechanical without impact) RTI
The electrical market covers a wide variety of applications with one commonality: the direct use of, or being in close proximity to, an electrical current.
Common applications include wiring devices, enclosures, switches, connectors, meters, and lighting. Each of these subcategories encompasses thousands of individual OEM products, whose material requirements differ. For example, a connector may be designed for the same core function whether it is located in a home office, on a US Navy Battleship, or down-hole in an oil well application, but the material selection process will follow very different paths.
The latest developments in plastics for electrical applications have focused on achieving flammability ratings at smaller and smaller thicknesses. Outside of specialty applications, the majority of electrical devices use engineering resins that are not inherently flame retardant. Flammability requirements are met by adding a flame suppressing agent into the compound. Resin manufacturers continue to develop advanced flame retardant compounds that offer equal performance at smaller thicknesses, all while continuing to use environmentally friendly raw materials.Conventus prides itself on being a key partner in both, continuous improvement and new product introduction, efforts at partner OEMs, by introducing, and educating customers on, the latest resin technologies.
Lighting is a subcategory within the broader electrical market with a unique set of requirements. In addition to the standard considerations, an emphasis on clarity (transparent, translucent, vs. opaque), thermal resistance, and thermal management is present. Typical applications include diffusers, housings, reflectors, lamp holders, and heat sinks.Some of the latest trends are outlined below:
Light-emitting diodes (LED) have quickly replaced traditional incandescent bulbs due to their significantly lower operating expenses, longer life spans, and lower carbon dioxide emissions. However, the highly concentrated light does create challenges for existing lenses. Using the same clear or milky lenses leaves the viewer seeing each individual LED vs. a single light source. To optimize aesthetics lighting companies have turned to a special diffusion pigment to scatter the light.
In most applications, OEMs are trying to achieve the delicate balance of creating just enough diffusion to hide the LEDs, while maximizing lumen output. Taking into account the thickness of the lens, as well as the distance between it and the LED, the amount of diffusion pigment can be dialed in to realize this balance.
Conventus has the following standard diffusion grades available in both PMMA and PC, but is constantly developing custom solutions as needed.
45% Light Transmission at 1mm & 2mm
55% Light Transmission at 1mm & 2mm
65% Light Transmission at 1mm & 2mm
75% Light Transmission at 1mm & 2mm
Another difference between LED and incandescent bulbs is the output generated. Incandescent bulbs produce 83% infrared light, 12% heat, and only 5% visible light. By contrast, LEDs supply 75% heat and 25% visible light. The large increase in heat normally requires the use of heat sinks in the design of a lighting assembly.
Thermally conductive compounds are formulated to transfer heat. The rate of heat transfer is measured in W/m-K. Since plastics are naturally insulative, large amount of fillers are used to facilitate conduction. There are two main types of fillers used – Carbon Fiber, which is both electrically and thermally conductive, and Ceramics, which only transfer heat.Studies have shown that convection is equally or more important than conduction in dissipating heat. Conventus can assist with the design of heat sinks in lighting applications.
Over the past five years, resin manufacturers have launched new Polycarbonate compounds that address a previous need in the lighting market. In years past, FR additives affected the clarity of PC resulting in a cloudy appearance. Today’s latest clear FR PC products offer the clarity of natural PC (87-88% Light Transmission) while pushing the boundaries of UL94 V0 in very thin walls.