Different axial/radial shrinkage rates of PTFE

The axial and radial shrinkage rates of cylindrical PTFE products are inconsistent. This type of defect mostly occurs in the thick-wall transition areas of the product and at the far end of the gate, and gradually appears in the cooling and shaping stage. This problem causes the product dimensions to exceed the tolerance range, affecting assembly accuracy and product function.

(1) Process factor: Uniaxial pressing during preforming causes orientation of molecular chains and fillers; this factor affects the '2079851475616104453 and final quality of the product. (2) Shrinkage control aspect: The shrinkage in the orientation direction is different from that in the perpendicular direction; uneven volume shrinkage causes internal stress and dimensional deviation. (3) Material aspect: The curing volume shrinkage rate of the resin system is relatively large, lacking effective constraint. (4) Process aspect: The curing rate is too fast, and the shrinkage stress has no time to relax and release. (5) Design aspect: Large wall thickness differences cause inconsistent shrinkage among regions.

(1) Implementation measure: Adopt isostatic pressing molding to eliminate the orientation effect, formulate specific operation plans in combination with actual production conditions, and verify the implementation effect. (2) Implementation measure: Consider the shrinkage rates in different directions separately when designing mold dimensions., formulate specific operation plans in combination with actual production conditions, and verify the implementation effect. (3) Formulation optimization: Add low-shrinkage additives or fillers to reduce the volume shrinkage rate of the system. (4) Process adjustment: Control the curing rate to avoid excessive shrinkage, and set a feeding structure at the gate. (5) Preventive measure: Establish a shrinkage rate database, preset shrinkage compensation amounts according to product structure and material type, and regularly calibrate mold dimensions.

The core of shrinkage defects lies in the contradiction between the volume change of material curing and insufficient process compensation, which needs to be comprehensively controlled through formulation optimization and process adjustment.