Lubricant Evaporation and Void Formation in PTFE Paste Extrusion

Lubricant evaporation and void formation are the most common internal defect problems in PTFE paste extrusion and post-processing. The volatile lubricants added in PTFE paste are necessary to ensure smooth extrusion molding, but the volatilization process of lubricants in extrusion, drying and sintering stages will directly affect the internal structural compactness of products. Uncontrolled abnormal lubricant evaporation will form a large number of tiny or continuous voids inside PTFE products, reducing product density, tensile strength, compression resistance and electrical insulation performance, and becoming the main hidden danger of product quality failure. Clarifying the formation mechanism of lubricant evaporation and voids is crucial for defect suppression and process optimization PTFE TUBE.

Abnormal lubricant evaporation in the extrusion stage is the primary cause of early void defects. In the extrusion process, excessively high die temperature and long material residence time will cause partial premature volatilization of lubricants before molding. The local lubricant loss leads to insufficient fluidity of partial paste, uneven particle stacking, and the formation of tiny gaps between particles. These gaps cannot be filled in the subsequent molding process and are retained in the extruded blank to form primary voids. In addition, too fast ram speed causes intense material shear heating, resulting in local temperature rise and instantaneous lubricant volatilization, forming scattered micro-voids inside the product.

In the drying and pre-sintering stage, unreasonable temperature rise curve is the main cause of secondary void expansion. The traditional one-time rapid heating process leads to violent and rapid volatilization of internal lubricants. The high-speed overflow of lubricant vapor will impact the unconsolidated PTFE particle structure, expand the original tiny gaps into large-size voids, and even form continuous pore channels inside the product, seriously damaging the structural compactness. Uniform gradient heating is the key to suppress void expansion: low-temperature slow drying removes surface lubricants, and staged temperature rise volatilizes internal lubricants stably, avoiding structural impact caused by rapid vapor overflow PTFE SHEET.

Lubricant content formula mismatch will also induce void concentration defects. Excessively high lubricant dosage increases the total volatilization amount in the product unit volume, and the residual voids after volatilization are large in quantity and high in porosity, resulting in loose product structure and reduced strength. Too low lubricant content leads to poor paste fluidity, incomplete particle filling during extrusion, and inherent gap defects, which will also form voids after sintering. Only the optimal lubricant ratio matching the product specification can balance extrusion fluidity and void rate, realizing low-void and high-compactness product molding.

In industrial defect control, comprehensive optimization measures are adopted to suppress void formation, including precise temperature control to avoid premature lubricant evaporation, gradient heating drying process to stabilize volatilization speed, optimal formula ratio to control total lubricant content, and stable extrusion parameters to ensure uniform particle filling. Through systematic control of lubricant volatilization behavior, the internal void rate of PTFE extruded products can be effectively reduced, the structural compactness and mechanical electrical properties of products can be significantly improved, and high-quality low-defect PTFE extrusion products can be produced.