Research on Application and Performance of Horizontal & Vertical Burning Tester Based on UL 94 Flammability Test

Abstract

Introduction

With the development of electrical and electronic products towards miniaturization, high density and high power, the flame retardant properties of insulating materials and engineering plastics directly determine the fire risk and fire safety of products. As an international general standard for flammability classification of plastic materials, UL 94 objectively classifies the flame retardant ability of materials through standardized burning tests, which is the core basis for product access, research and development selection and quality certification. As a special equipment for implementing UL 94 flammability test, the horizontal vertical burning tester realizes quantitative evaluation of material combustion behavior through controllable flame, precise flame application and multi-dimensional observation.

LISUN HVR-LS Horizontal Vertical Burning Tester is designed for the evaluation of HB&V grade (50W) and 5V grade (500W) materials, compatible with domestic and foreign standards such as GB/T 5169 series, IEC 60695 series, UL 94, GB/T 2408-2008, etc. It is widely used in R&D, production and quality inspection of lighting, low-voltage electrical appliances, household appliances, electric tools, electronic components and other industries, providing stable, accurate and reproducible test conditions for UL 94 flammability test. Combined with the structure and parameters of the instrument, this paper deeply analyzes the test process, index system and judgment logic of UL 94 flammability test to provide technical support for the standardized application of the industry.

HVR-LS Horizontal Vertical Flame Tester

Principle of UL 94 Flammability Test and Horizontal Vertical Burning Test Mechanism

Core Positioning of UL 94 Flammability Test
UL 94 flammability test focuses on the flaming combustion behavior of plastics and solid combustible materials. Through horizontal and vertical placement states, it simulates fire scenarios in actual use. Taking burning rate, after-flame time, after-glow time, burning length and melt dripping ignition as core criteria, materials are classified into HB, V-0, V-1, V-2, 5VA, 5VB and other grades, and the higher the grade, the better the flame retardant performance. The horizontal combustion corresponds to HB grade, and the vertical combustion corresponds to V grade and 5V grade, which are the most commonly used evaluation paths for electrical and electronic products.

Core Mechanism of Horizontal Vertical Burning Test
The test uses a Bunsen burner as the standard burner, adopts methane or propane as the gas source, strictly controls the flame height, flame application angle, flame application duration and sample posture, applies controlled flame to standard size samples, observes and records key data in the whole combustion process, and judges the grade according to the UL 94 threshold.

• Horizontal mode: Evaluate the flame spread speed along the sample surface and determine HB grade;
• Vertical mode: Evaluate the self-extinguishing ability of the sample, the duration of after-flame and after-glow, and the risk of melt dripping, and determine V-0/V-1/V-2/5V grade.

LISUN HVR-LS realizes the full-process standardization of flame parameters, flame application action and observation indicators through high-precision gas circuit, servo positioning and millisecond-level timing, ensuring the consistency and reliability of UL 94 flammability test results.

Technical Parameters of LISUN HVR-LS Horizontal Vertical Burning Tester (Adapted to UL 94)

The instrument is optimized for UL 94 flammability test, and the key parameters fully cover the standard requirements, as follows:

Test Process of UL 94 Flammability Test (Based on HVR-LS)

Sample Preparation
Prepare standard samples according to UL 94: 125mm×13mm×thickness (commonly 1.5–13mm). After temperature and humidity pretreatment, install them in the fixture, fix horizontally or vertically, and place absorbent cotton below to detect melt dripping ignition.

Flame Calibration
Start LISUN HVR-LS, adjust gas pressure and flow, calibrate the flame height to 20mm (50W) or 125mm (500W), and confirm that the flame shape is a stable blue inner flame, meeting the requirements of UL 94 for flame power and geometric parameters.

Horizontal Burning (HB Grade)
The sample is inclined 45° horizontally, the flame acts on the free end at 45°, move away the flame after 30s of application, record the time and burning length when burning to the 25mm and 100mm marking lines, and calculate the burning rate.

Vertical Burning (V-0/V-1/V-2)
The sample is hung vertically, and the flame acts vertically on the lower end. Apply flame twice for 10s each time, record after-flame time and after-glow time, and observe whether the melt drips ignite the absorbent cotton below. Repeat the test on 5 samples and judge the grade according to UL 94 thresholds.

5V Grade (500W) Test
Adopt higher power flame, apply flame circularly at 20°, evaluate flame retardant performance under extreme conditions, suitable for high-safety scenarios. LISUN HVR-LS can directly support it through optional components.

Comparison of Core Indicators for UL 94 Flammability Test Grade Judgment

Instrument Advantages and Support for UL 94 Flammability Test

• Full Standard Compatibility: Simultaneously meet UL 94, GB/T 2408, IEC 60695, GB 4943, etc., one test meets multi-standard output and reduces certification costs.
•  High Precision Control: Millisecond-level timing, micron-level positioning, stable gas circuit, ensuring that the measurement error of UL 94 key indicators is better than the standard allowable range.
•  Full Grade Coverage: Support full-grade tests of HB, V-0/V-1/V-2, 5V, suitable for R&D and quality control from general plastics to high-performance flame-retardant materials.
•  Long-term Stability: LISUN HVR-LS has been marketed for more than ten years, with reliable structure and easy maintenance, meeting the high-frequency test needs of laboratories and production lines.

 Conclusion and Prospect

UL 94 flammability test is a key technical means to ensure the intrinsic safety of products in the electrical, electronic and materials industries. The horizontal vertical burning tester is the core equipment to realize the standardization and quantification of this test. With precise flame control, full parameter adjustment, multi-standard compatibility and high stable operation, LISUN HVR-LS provides a complete solution for UL 94 flammability test, which can efficiently output key data such as after-flame, after-glow, burning length and melt dripping behavior, supporting material flame-retardant modification, product structure optimization and quality compliance control.

With the rapid iteration of new energy, intelligent terminals and automotive electronics, material flame retardant requirements continue to increase, and UL 94 flammability test will become stricter. The horizontal vertical burning tester will develop towards automation, digitization and visualization. LISUN HVR-LS series continues to iterate, providing more efficient, intelligent and compliant testing tools for the industry, helping to upgrade product safety performance and access to the international market.