The waterproof breathable vent membrane PTFE is a highly crystalline polymer with a maximum crystallinity of 92% to 98%. However, after processing or sintering cooling, the crystallinity is reduced to no more than 70% of the raw meal crystallinity. PTFE exhibits a spatial helical conformation of 180 rotation for every 13 links at 19 C. The number of chain units required for rotation above 19 C also increases to 15, because the distance of each link increases to 0.195 nm. This change means that the hardness of powdery particles is below 19 and above. When the temperature is above 19 C, the bond has some degree of angular displacement, which increases with the temperature rising; when the temperature is above 30 C, the displacement tends to increase continuously until 327 C. This means that particles above 19 degrees are soft and easy to deform. This is of great guiding significance to the selection of PTFE resin post-treatment process, the design of material moving mode and equipment on the pipeline, the determination of packaging mode and storage temperature, and also to the selection of film temperature by stretching method after paste extrusion of dispersed PTFE resin.

The crystalline state of PTFE is a triclinic lattice when the temperature is below 19 C. At 19 C, the transformation of the crystalline form occurs, the rotation degree of the chain becomes slightly smaller, and the unit lattice becomes a hexagonal system. At 30, the crystal relaxation of PTFE crystal and the rotation of bond order become random winding. These two temperature points are usually referred to as phase transition points.

The high crystallinity and high molecular weight of waterproof permeable film PTFE resin lead to the high melting viscosity of PTFE. The kinematic viscosity measured at 380 ~1011Pa. s also has no fluidity at melting point temperature. Therefore, ordinary PTFE resin can not be processed by the usual processing method which is suitable for fusible processing plastics. Suspended PTFE resin can only be processed by similar powder metallurgy method, i.e. suspended PTFE resin powder is placed in the die to be pre-formed by compression, while dispersed PTFE resin needs to be pasted by adding a booster (lubricant). They must be sintered before forming products.