# Preparation and Material–Structure–Performance Relationships of Biaxially Stretched Polytetrafluoroethylene (PTFE) Membranes for Air Filtration

## TL;DR

This study explores how the properties of PTFE resins affect the performance of air filtration membranes, revealing key relationships between material characteristics and filtration efficiency.

## Contribution

The paper establishes a hierarchical material–structure–performance relationship for biaxially stretched PTFE membranes.

## Key findings

- Higher molecular weight and lower particle-size dispersion result in finer fibers and narrower pores, improving filtration efficiency.
- Increased pressure drop and reduced quality factor indicate a trade-off between efficiency and flow resistance.
- Mismatch between resin properties and processing conditions leads to structural degradation and poorer performance.

## Abstract

Biaxially stretched polytetrafluoroethylene (PTFE) membranes are promising media for high-efficiency air filtration because of their stable node–fiber microstructure and environmental durability. To clarify how resin properties and microstructure govern filtration behavior, ten PTFE resins with different average molecular weights (Mn) and particle size characteristics were processed into membranes under essentially identical biaxial stretching and sintering conditions. Resin particle size, fiber diameter and pore size distributions were quantified, and coefficients of variation (CVs), together with Spearman rank correlations, were used to analyze material–structure–performance links. Filtration efficiency, pressure drop and quality factor (QF) were measured according to ISO 29463-3 using 0.1–0.3 μm aerosols. Higher Mn combined with lower particle-size dispersion favored finer fibers and narrower pores, yielding efficiencies close to 100%, but increased pressure drop and slightly reduced QF, indicating a trade-off between efficiency and flow resistance. The sample with the lowest Mn in its group and a high machine-direction draw ratio (12×), showed pronounced fibril breakage, node coalescence, broadened pore-size distribution and degraded QF, illustrating the sensitivity of structure and performance to resin-process mismatch. Overall, the study establishes a hierarchical material–fiber–pore–performance relationship that can guide resin selection, structural tuning and process optimization of biaxially stretched PTFE membranes.