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Understanding Flame Retardant Polycarbonate

November 05, 2019

One of the more common questions customers ask is in regards to the flame rating or flammability of polycarbonate. Often times, the individual is trying align a building code with the material’s flammability rating.

There are several flammability tests. Some test the time it takes for the material to self-extinguish. Other tests will determine flame spread and/or the burn rate. The testing method may orient the material differently, such as vertically or horizontally. Separate from the flammability, especially in the transportation industry, materials have to pass heat release, smoke density, and smoke toxicity tests related to burning material.

The simplest answer to the customer’s question is that Total Plastics offers material that meets the UL 94 rating and/or Total Plastics offers material that conforms to most local and state flammability building code requirements. Which material would depend exactly on the flammability rating required.

Polycarbonate for Building & Construction

Polycarbonate is commonly sought out by contractors for use in building and construction due to its conformance to flammability ratings, as well as its high impact strength, formability, optical clarity, and light weight. Regarding its strength, polycarbonate has the ability to withstand direct impacts without breaking, whereas a comparable materials like glass or acrylic may crack or shatter. That is why polycarbonate is commonly sought out for security and ballistic applications.

Total Plastics is a distributor of LEXAN Polycarbonate Sheet. General Purpose LEXAN, or LEXAN 9034, is rated to UL 94 HB. LEXAN 9604 is rated UL 94 V-0 for 90 mils and above and V-2 for 34-89 mils.

In addition to building and construction, polycarbonate is commonly used in aerospace and rail applications for its conformance to flammability and smoke density requirements, as outlined by the FRA and FAA.

Understanding Building Codes

When selecting the right material for a project, it is critical to follow the building code in the jurisdiction where the structure is located.

There are city, state, county and municipality building codes. There are no “federal” building codes, per se, but we’ll get into that in a second. A city may defer to or adopt a state’s building code. For instance, Total Plastics is located in Kalamazoo, MI. According to section 9-22 of the Kalamazoo’s building code, it outlines the adoption of the Michigan Building Code. The Michigan Building Code is adopted, with amendments, from the International Building Code (IBC). The IBC is a foundational set of codes to ensure the quality construction of commercial and residential structures.

Adopting the ICC Code

The International Code Council (ICC) developed the IBC, which has been adopted by most jurisdictions in the U.S. Amendments may exist for a specific city or state building code. According to Federal Emergency Management Administration (FEMA), “Rather than create and maintain their own codes, most states and local jurisdictions adopt the model building codes maintained by the ICC.”

The ICC’s code was formalized in 1994, updated every three years, and was created from a handful of regional building codes that predated it. The use of the word “international” can be a little misleading, as this code was developed for the U.S. and by a panel U.S. residents. It has been adopted by countries other than the U.S., thus “international.”

As for a “federal” building code, according to the General Services Administration (GSA), an independent agency of the U.S. government that works will all other federal agencies for the supply of products and services, “For all design and construction work performed on federal buildings … the GSA has adopted the technical requirements of the following nationally recognized codes referred to in this subsection.” The referenced code is the ICC’s building code.

IBC Fire Prevention

A major focus of the IBC addresses fire prevention from a materials and construction standpoint. For example, in a document that outlined proposed changes to the IBC, one section dealt primarily with the use of the term “non-combustible” and what was an agreed upon definition for it. IBC consultants are continually evaluating the testing methods and results to ensure the safest building practices.

To that end, it’s important to note that material is not “approved for” any specific applications, but rather the testing method on the sample material showed that it performed to the application demands.

UL Rated Building Material

The Underwriters Laboratories (UL) is an independent, non-profit testing laboratory. Through UL’s testing methods, it validates and certifies a manufacturer’s claims about its product’s performance. It will also test material against existing codes and standards. Fire, smoke and flammability testing is one of its many diagnostic services.

UL does not approve material for application, so UL designations are either UL Listed, UL Recognized or UL Certified. UL listed means the product was tested and meets the laboratory standard. UL Recognized is more for a finished product with different components. UL Certified is the designation that contractors will want to pay attention to, as it designates that the material was tested against an existing standard, such as a building code.

UL 94 Flammability Rated Polycarbonate

Let’s start with the UL 94 standard, which is titled “Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances.” LEXAN 9034, which is the LEXAN general purpose polycarbonate sheet, is listed as “flame-resistant” by the manufacturer. LEXAN 9034 is an uncoated sheet and the standard grade of LEXAN sheet.

There are six different flammability ratings under UL 94: 5VA, 5VB, V-0, V-1, V-2 and HB.

  • The Horizontal Burn (HB) rating is the lowest of the UL 94 ratings and indicates the material as self-extinguishing. LEXAN 9034 is UL 94 HB rated.
  • A V-2 (vertical burn) rating indicates the burning will stop within 60 seconds after two applications from ignition source of 10 seconds each. A flaming drip of material is allowed.
  • A V-1 rating is similar to the V-2 rating with the exception that no flaming drip of material is allowed.
  • A V-0 rating indicates the material stops burning much faster than V-2 or V-1, stopping after 10 seconds while also not allowing any flaming drips of material.
  • A 5VB surface burn rating means the material was exposed to ignition source for 5 seconds, 5 times and stopped burning within 60 seconds. The material may have burn through.
  • A 5VA rating is the highest material rating or most flame retardant. It has the same parameters of the 5VB test, but no burn through.


  • ASTM D 1929

    ASTM D635 test the rate of burning (and/or extent) and the time of burning plastic in a horizontal position. The ICC’s IBC requires this test for light-transmitting plastic, which is an applicable common for polycarbonate sheets.

    Many grades of LEXAN Polycarbonate Sheet have a self-ignition temperature of about 1000 degree Fahrenheit, well about the ASTM D standard of 650 degree Fahrenheit. Many LEXAN Polycarbonate Sheet grades also have a CC1 classification, meaning they self-extinguish between 0.4 and 1 inch.