ePTFE microporous membrane folding filter element: Innovation and breakthrough in welding technology

ePTFE Microporous Membrane Folded Filter Elements
As an ultra-fine filtration device (commonly referred to as "filter elements"), these are widely used for sterilization filtration in pharmaceutical, biopharmaceutical, and biochemical testing applications, as well as for separation and purification in chemical engineering, beverage production, semiconductor electronic rinsing, and water treatment. The filter element is constructed by coating a specialized polymer chemical material into an ultrathin microporous membrane through a unique adhesive process. This membrane is then folded with support layers on both sides, rolled into a cylindrical filtration layer, and finally welded with plastic inner/outer cylinders and end caps to form an integrated structure. During filtration, media passes through the micropores while larger particles are retained, achieving separation.

Sealing Welding Quality Control
To ensure high performance and preserve the microstructure of the filter element, strict control of welding conditions is mandatory during the sealing weld between the filtration layer and the inner/outer cylinders/end caps. The performance test results of the microporous membrane serve as critical criteria for evaluating sealing weld quality.

Current Status of Domestic Welding Technology
China’s welding technology for ePTFE microporous membrane folded filter elements has reached a certain scale, with continuous improvements in quality. However, significant gaps remain compared to international brands. Domestic production primarily employs hot plate welding technology: a heated template is pressed onto the welding surfaces of components for a predetermined duration, then rapidly removed to allow fusion and cooling of the bonded surfaces.

Advantages of Hot Plate Welding
This method offers unique benefits, including real-time monitoring and control of melting time/temperature via timers and temperature sensors, as well as flexible parameter adjustments through PLC software. Its rapid cycle time also makes it ideal for mass production.

Limitations of Hot Plate Welding
Being a direct-contact heating method, it carries a high risk of plastic adhesion. While high-temperature-resistant Teflon anti-adhesive coatings can isolate the welding surface from the template, the stringent temperature and fluidity requirements for sealing welds pose challenges. At 22°C room temperature, if the system’s mechanical response time exceeds 3 seconds, maintaining stable welding parameters becomes difficult. Compensating by raising the mold temperature often degrades the Teflon coating’s anti-adhesion properties, accelerating aging and compromising weld quality.

Innovative Welding Solutions by Shanghai Puxiong
To address these issues, Shanghai Puxiong introduced a novel end-cap heating method. After years of R&D and extensive trials, a groundbreaking welding technique has been developed. This innovation significantly enhances the welding technology for ePTFE filter elements, improving both production consistency and comprehensive performance metrics. The method is adaptable to both single-station small-batch and multi-station automated mass production.

Case Study: Single-Station Welding Equipment
The redesigned equipment optimizes mechanical hardware and integrated control software based on the unique requirements of filter element sealing welds. It replaces the traditional dual-cylinder pushing mechanism for end caps, eliminating issues like poor synchronization accuracy and uncontrollable welding speeds. Enhanced mechanical-electrical coordination and user-friendly debugging modes ensure optimal parameter calibration for flawless weld outcomes.