UL’s Comprehensive Testing for Flame‑Resistant Plastic Components

Ensuring flame resistance in plastic components is critical for safety‑first designs, whether you’re building engines, electrical systems, or fire‑fighting equipment.

How do you verify that a plastic part will resist ignition, and how long that resistance will last under real‑world exposure? The answer lies in rigorous testing and certification by a trusted authority.

Underwriters Laboratories (UL) is a globally recognized, non‑governmental safety consulting and certification organization headquartered in Northbrook, IL. Approved by the U.S. Occupational Safety and Health Administration (OSHA) and listed as a Nationally Recognized Testing Laboratory, UL is a non‑profit institution founded in 1894. Over more than a century, UL has developed the safety standards that underpin many of the Industrial Revolution’s breakthroughs, including the widespread adoption of electricity.

In 2010, UL reorganized into five core business units—Product Safety, Verification Services, Life & Health, Knowledge Services, and Environment—serving a broad spectrum of industries. By 2012, 69,007 manufacturers had partnered with UL to produce 22 billion UL‑marked products. In that same year, UL evaluated 92,442 individual items across 104 countries and employed 10,387 professionals in 39 nations. Craftech noted in the late 1980s that UL had only 3,500 employees; the growth trajectory is unmistakable.

UL’s six‑fold service portfolio includes:

1. Certification
2. Testing
3. Inspection
4. Auditing
5. Validation
6. Advisory and Education

Clients pay for these services, submitting their products for evaluation. When a component already bears a UL mark, the final product certification can proceed more swiftly.

Assessing plastic flammability relies on UL’s UL 94 and UL 746A standards. These tests examine a range of conditions—from ultraviolet exposure and water immersion to ignition from electrical sources, such as overheated conductors or arcing connections. Results populate the UL iQ™ database, enabling subscribers to filter materials by specific criteria.

UL also developed the QMQS2 standard to assess color concentrates mixed with natural resin, facilitating cost‑effective custom‑colored plastics. UL 746A specifically measures resistance to ignition from electrical sources.

Scope of UL 94 (six parts):

1. Provides general guidance; results are indicative and should be corroborated with application‑specific testing.
2. Designed for small‑scale, controlled laboratory testing—not for use in untested environments.
3. Recommends UL 1694 for components too thin for UL 94 minimum thickness requirements.
4. Does not predict performance outside the test conditions; factors such as size, shape, and environment influence flammability.
5. Applicable to non‑metallic materials beyond plastics, when appropriate.
6. Not applicable to components exceeding 13.0 mm thickness or 1 m² surface area, nor to building construction or finishes.

UL assigns 12 flame classifications—marked with an “H” (horizontal) or “V” (vertical)—based on laboratory results. These classifications, such as 5VA, 5VB, V‑0, V‑1, V‑2, and HB, indicate how quickly a material self‑extinguishes after flame removal and whether flaming particles can ignite a secondary surface. Most plastics used in Craftech’s products fall into the first group, ideal for enclosures, structural parts, and insulators in consumer electronics.

*Statistics sourced from UL’s website.

Curious which UL 94 ratings the most popular materials receive? Download our High Performance Plastics Material Guide to explore detailed ratings.