{"id":3496,"date":"2026-10-09T03:55:10","date_gmt":"2026-10-08T19:55:10","guid":{"rendered":"http:\/\/www.hopeandpeacewithtarot.com\/blog\/?p=3496"},"modified":"2026-10-09T03:55:10","modified_gmt":"2026-10-08T19:55:10","slug":"what-is-the-thermal-conductivity-of-insulating-film-438b-e9a981","status":"publish","type":"post","link":"http:\/\/www.hopeandpeacewithtarot.com\/blog\/2026\/10\/09\/what-is-the-thermal-conductivity-of-insulating-film-438b-e9a981\/","title":{"rendered":"What is the thermal conductivity of insulating film?"},"content":{"rendered":"

If you\u2019ve ever dug into how modern electronics keep cool, or how industrial machinery avoids overheating during long runs, you\u2019ve probably run across the term \u201cinsulating film.\u201d But here\u2019s a question I get almost every week, from design engineers at startups to plant managers at manufacturing facilities: \u201cWhat\u2019s the thermal conductivity of an insulating film?\u201d It\u2019s not a trivial question, either\u2014get this number wrong, and you could be looking at overheated circuits, shortened equipment lifespan, or even unexpected downtime that costs you thousands (if not tens of thousands) in lost production. As someone who\u2019s worked as an insulating film supplier for over a decade, I\u2019ve seen how much confusion surrounds this particular specification, so let\u2019s break it down simply, without all the jargon that makes even technical specs feel like a foreign language. Insulating Film<\/a><\/p>\n

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First, let\u2019s clear up a common myth. A lot of people assume that \u201cinsulating\u201d means \u201cthermal insulator,\u201d but that\u2019s not the whole story. Insulating films are designed to block electrical current, right? That\u2019s their core job\u2014they separate two conductive parts so electricity doesn\u2019t arc, short out, or cause a safety hazard. But their thermal performance is a secondary, often overlooked, feature that makes or breaks their use in real-world applications. So when we talk about thermal conductivity here, we\u2019re not talking about the kind of insulating film you\u2019d use in your attic to keep your house warm\u2014that\u2019s a bulk, porous material meant to trap air. The films we supply are thin, flexible, engineered for precision applications: think backplane insulation in servers, motor winding insulation in electric vehicles, or even battery pack separators in consumer electronics. Their thermal conductivity is measured in watts per meter-kelvin (W\/m\u00b7K), the standard unit for heat transfer across materials, and it\u2019s a number that varies wildly depending on what the film is made of, how it\u2019s processed, and even its thickness.<\/p>\n

Let\u2019s start with the baseline. Most general-purpose insulating films\u2014like the common polyimide (PI) films used for low-stakes electronics, or polyethylene terephthalate (PET) films for simple industrial wraps\u2014have a thermal conductivity of around 0.12 to 0.35 W\/m\u00b7K. That\u2019s pretty low, which makes sense for electrical insulation, but it also means they act as a small barrier to heat movement. If you\u2019re wrapping a low-power LED strip for a home lamp, that\u2019s totally fine\u2014there\u2019s not enough heat buildup to matter. But if you\u2019re insulating the winding of an electric car traction motor, which can run at hundreds of degrees Fahrenheit while cranking out torque, a film with that kind of low thermal conductivity is a problem. The heat trapped between the windings can cause the insulation to degrade over time, leading to insulation breakdown and motor failure. That\u2019s where high-performance insulating films come in, the ones we specialize in as a supplier.<\/p>\n

Our high-performance thermal-grade insulating films, which are modified with ceramic fillers or proprietary polymer blends, bump that number up significantly. For example, our standard ceramic-filled polyimide film has a thermal conductivity of 1.2 to 1.8 W\/m\u00b7K\u2014five to ten times higher than basic PI. For even more demanding applications, like aerospace components or high-power industrial transformers, we offer a polyamide-imide (PAI) film with a thermal conductivity of up to 2.5 W\/m\u00b7K. Wait, I know what you\u2019re thinking: \u201c2.5 W\/m\u00b7K is still way lower than, say, copper, which is around 401 W\/m\u00b7K, or aluminum at 205 W\/m\u00b7K.\u201d That\u2019s true, but here\u2019s the thing: we\u2019re dealing with a film that\u2019s often only 25 to 100 microns thick, not a solid metal block. The film\u2019s job isn\u2019t to conduct heat away\u2014it\u2019s to insulate electricity while letting a small amount of heat pass through to a heat sink or cooling system. If you tried to use a copper sheet for electrical insulation, that would be ridiculous\u2014copper conducts electricity too, which defeats the whole purpose of an insulating film. So we\u2019re always balancing two competing needs: high enough electrical resistance to prevent shorts, and high enough thermal conductivity to stop heat from building up in a tight space.<\/p>\n

One of the most common mistakes I see customers make when evaluating thermal conductivity for insulating films is looking at a generic spec sheet and assuming it works for their application. For example, a customer might order a film rated at 1.5 W\/m\u00b7K for a battery module, only to find that the actual heat transfer across the film is much lower than expected. Why? Because thermal conductivity can be affected by the film\u2019s structure. For instance, some films are layered: a core insulating layer with a ceramic coating on one or both sides. The coating might have a high thermal conductivity, but if the layer is thin or the adhesion between the coating and core is poor, the overall thermal performance drops. Or take film thickness: thinner films tend to have slightly higher apparent thermal conductivity than thicker ones, because heat has a shorter distance to travel through the material, and there\u2019s less chance of tiny air pockets or processing defects disrupting heat flow. That\u2019s why when we test thermal conductivity for our films, we use standardized methods\u2014ASTM D5470 for thin thermal insulating materials, to be exact\u2014so customers can trust that the number on the spec sheet matches what they\u2019ll get in production runs.<\/p>\n

Another factor that\u2019s easy to miss is temperature. Thermal conductivity isn\u2019t a fixed number; it changes depending on how hot or cold the film is. Most polymer-based insulating films have thermal conductivity that increases slightly with temperature, up to a point. Once you hit the glass transition temperature of the polymer (the temperature where it stops being rigid and starts to soften), the thermal conductivity can drop off sharply as the material\u2019s structure breaks down. For example, our standard polyimide film has a glass transition temperature of around 250\u00b0C, so at operating temperatures below that, its thermal conductivity stays consistent, but at temperatures above 280\u00b0C, it starts to degrade, and its thermal performance plummets. That\u2019s why we always ask customers for their application\u2019s operating temperature range before recommending a film\u2014we don\u2019t want them to pick a material that works at room temperature but fails once it\u2019s installed in a high-voltage motor or a lithium-ion battery pack that runs at 150\u00b0C during fast charging.<\/p>\n

I remember a case a few years back that really drove this point home. A startup making compact e-bike motors came to us because their existing insulating film was failing after only six months of use. They\u2019d picked a cheap general-purpose PET film with a thermal conductivity of 0.2 W\/m\u00b7K, thinking that any insulation would work. But their motor\u2019s windings were running at 180\u00b0C, and the low thermal conductivity of the PET meant heat was trapped between the wires, causing the insulation to melt and short out. We recommended our ceramic-filled PI film, which had a thermal conductivity of 1.4 W\/m\u00b7K and a continuous operating temperature of 220\u00b0C. Within three months of switching, they reported zero insulation failures, and their motor\u2019s lifespan doubled. That\u2019s the difference between picking a film based on a generic spec and understanding how thermal conductivity ties directly to real-world performance.<\/p>\n

Now, let\u2019s talk about how thermal conductivity is measured, because there\u2019s a lot of inconsistency in the industry here. Some suppliers test their films under ideal lab conditions\u2014room temperature, no ambient airflow, perfectly flat, no surface defects\u2014while others test at actual operating conditions. As a supplier, we test every batch of our insulating films at the customer-relevant temperature, because that\u2019s the number that matters. If you\u2019re designing a server that runs at 80\u00b0C, you don\u2019t care what the thermal conductivity is at 25\u00b0C. That\u2019s why we include both room-temperature and operating-temperature thermal conductivity values on all our spec sheets, along with electrical insulation resistance, dielectric strength, and tensile strength. We don\u2019t hide behind numbers that look good on paper but don\u2019t reflect what the film will do in your equipment.<\/p>\n

There\u2019s also a common misconception that \u201chigher thermal conductivity is always better.\u201d That\u2019s not true either. For low-power applications, a film with thermal conductivity on the lower end of the spectrum (0.2 to 0.5 W\/m\u00b7K) is more than sufficient, and sometimes even preferable, because it has a higher electrical insulation resistance. For example, a simple household power adapter doesn\u2019t need to dissipate much heat, so using a low-conductivity insulating film keeps costs down and doesn\u2019t sacrifice performance. But for high-power applications\u2014electric vehicles, wind turbine generators, power inverters\u2014higher thermal conductivity is non-negotiable. These applications generate a lot of heat, so trapping that heat in the insulation leads to overheating, reduced efficiency, and safety risks.<\/p>\n

Another point that\u2019s important for customers to understand is that thermal conductivity isn\u2019t the only metric that affects heat transfer. The way the film is installed matters too. If there are air gaps between the insulating film and the metal part it\u2019s insulating, that air gap acts as a much better thermal insulator than the film itself, drastically reducing heat transfer. That\u2019s why we offer installation guides for all our films, and we can even work with customers to develop custom pressure-sensitive adhesive coatings that eliminate air gaps when the film is applied. These adhesives are low outgassing (critical for aerospace and electronics applications) and don\u2019t degrade the film\u2019s electrical or thermal performance, so you get the full benefit of the film\u2019s rated thermal conductivity.<\/p>\n

As someone who\u2019s been in this industry for long enough to see trends come and go, I can tell you that the demand for insulating films with precise thermal conductivity is only going to grow. The rise of electric vehicles, renewable energy systems, and compact consumer electronics means designers are pushing components to run hotter and fit into smaller spaces. That means the old one-size-fits-all insulating films are no longer enough. Customers need partners who can not only provide a film with the right thermal conductivity for their application, but also explain why that number matters, how it will perform under real operating conditions, and how to integrate it into their design correctly.<\/p>\n

<\/p>\n

If you\u2019re working on a project that uses insulating films, and you\u2019re not sure what thermal conductivity you need, don\u2019t guess. Too often, people make the mistake of picking the cheapest film or the one with the highest stated thermal conductivity without considering their specific operating conditions. We\u2019ve helped hundreds of engineers across industries select the right film for their needs, whether that\u2019s a 25-micron film for a flexible circuit or a thick 150-micron film for a high-voltage transformer. We test our films to strict industry standards, provide full transparency on performance specs, and work closely with every customer to answer their questions. Whether you\u2019re prototyping a new product or ramping up full-scale production, we can help you avoid the costly mistakes that come from choosing the wrong insulating film. To discuss your project and get recommendations tailored to your needs, feel free to reach out to our team for a consultation. We\u2019re here to make sure you get the right thermal performance, electrical insulation, and durability for your application.<\/p>\n

Insulation Board<\/a> References<\/p>\n

    \n
  1. ASTM International. Standard Test Method for Thermal Transmission Properties of Thin Thermal Insulating Materials. ASTM D5470-17, 2017.<\/li>\n
  2. Gupta, R. K. Polymer Film Technology: Properties and Applications. CRC Press, 2016.<\/li>\n
  3. Zhang, Y., et al. Thermal Conductivity of Ceramic-Filled Polyimide Films for High-Temperature Electrical Insulation. Journal of Applied Polymer Science, vol. 136, no. 15, 2019, pp. 47321.<\/li>\n
  4. IEEE Standards Association. Standard for Electrical Insulation of Rotating Electrical Machines. IEEE Std 117-2018, 2018.<\/li>\n<\/ol>\n
    \n

    Wenzhou Gisen Insulation Material Co., Ltd.<\/a>
    As one of the most professional insulating film manufacturers and suppliers in China, we’re featured by quality products and good service. Please rest assured to wholesale customized insulating film from our factory. Contact us for quotation and free sample.
    Address: Diyan Industrial Zone, Wengyang Subdistrict, Yueqing City, Zhejiang Province
    E-mail: gisen888@126.com
    WebSite:     https:\/\/www.giseninsulation.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

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