The core characteristics and welding difficulties of ETFE membrane materials

ETFE (ethylene tetrafluoroethylene copolymer) membrane is an ideal material for tensile structure buildings (such as stadiums, greenhouses, and landscape domes) due to its high light transmittance, lightweight durability, and self-cleaning properties. However, its low surface energy and narrow melting window impose stringent requirements on welding processes.

Physicochemical Properties

High Light Transmittance:
Transmittance exceeds 95%, comparable to glass. However, microcracks or pores generated during welding can reduce transparency.

Low Surface Energy:
Contact angle > 100°. Molten material tends to adhere to tools, requiring special surface treatment or non-contact welding methods.

Narrow Melting Window:
Melting point ranges from approximately 260–300°C. Decomposition occurs above 320°C, producing toxic fluorides (e.g., HF), necessitating precise temperature control.

High Thermal Expansion Coefficient:
Linear expansion coefficient reaches 200×10⁻⁶/°C. Thermal deformation must be compensated during welding to prevent stress-induced cracking.

Challenges in Conventional Welding Methods

Hot Air Welding:
Non-uniform heating from hot air guns easily causes localized overheating. Weld seams tend to be wide (>5 mm), resulting in significant loss of light transmittance.

High-Frequency Induction Welding:
ETFE is non-conductive and cannot be directly heated via eddy currents. Conductive coatings (e.g., silver paste) are required, increasing cost and process complexity.

Mechanical Press Welding:
Pure pressure welding often leads to incomplete fusion defects, resulting in low weld strength (typically <50% of the base material).