When PTFE high-temperature tape is applied to a heat sealer, guide roller, or bonding surface, two common problems can appear at the edges: adhesive oozing (glue seeping out from the cut edge) and edge lifting (the tape edge peeling away from the substrate).
These defects are often traced back to one source: the quality of the slitting (cutting) process. The structure of the cut end face – whether smooth or rough, clean or delaminated – determines how the adhesive behaves at the edge.
Aokai PTFE controls slitting quality to prevent these issues. This guide explains how end face morphology causes oozing and lifting, and what a properly slit tape edge should look like.
The Structure of a PTFE Tape Cross-Section
To understand how the cut end face affects performance, first recall the tape’s structure. PTFE high-temperature tape typically consists of:
Slitting refers to longitudinally cutting this laminated composite into narrower rolls. The morphology of the cut end face – smooth or rough, straight or wavy – and dimensional regularity (flatness, verticality, adhesive shortage or stringing) trigger the two defects.
How the Cut End Face Causes Adhesive Oozing
Adhesive oozing means unintended seepage of adhesive from the tape edge, contaminating bonded workpieces or the tape reverse side. The cut end face exerts a direct influence.
1. Pulling and stringing effect from the cut
If the slitting blade is dull or the cutting angle is inappropriate, the blade will pull and stretch the flexible silicone PSA instead of cutting it cleanly. This causes:
Microscopic glue filaments and burrs: The torn adhesive leaves ultra-fine glue threads or flakes protruding from the tape edge. These "glue whiskers" easily transfer and break during processing or storage, creating the visual effect of adhesive oozing.
Adhesive migration toward edges: The pulling force during slitting drags adhesive onto the end face and even the cross-section of the substrate. When the tape is wound into a roll, the extruded adhesive sticks to the PTFE back of the adjacent layer. Upon unwinding, residual glue appears along edges – the classic oozing failure.
2. Extrusion effect from uneven end faces
Poorly regular end faces (wavy surfaces, protrusions, inclined planes) bear abnormal lateral pressure at raised points when the tape is tightly wound into rolls. Silicone PSA is viscoelastic – it creeps under sustained pressure, especially during high-temperature storage or transport. This pressure drives adhesive to flow from high-pressure protrusions to low-pressure voids, squeezing out from the end face.
3. Broken edge seal between adhesive and substrate
Ideal slitting delivers a flush cross-section integrating all layers. Poor slitting may cause delamination and separation between adhesive and fiberglass, or cavities on the cross-section, breaking the sealed edge structure. When heated, softened adhesive seeps outward through these micro-channels. At high temperatures (e.g., heat sealers above 200°C), adhesive fluidity surges, and rough end faces drastically raise the risk of oozing.
How the Cut End Face Causes Edge Lifting
Edge lifting refers to the spontaneous separation of tape edges from bonded surfaces under tension or heat after application.
1. Thinned edge adhesive layer – weak bonding zone
Dull blades or improper slitting parameters produce a compression-cut effect: the blade squeezes the material aside rather than slicing it cleanly. Adhesive flows laterally under compression, leading to extremely thin or even missing adhesive at the outermost edge. This marginal zone has far lower bonding force than the tape body, so edge lifting initiates here under minor tension or thermal stress.
2. Substrate burrs and delamination – wedging effect
PTFE tape substrate contains glass fiber. Improper slitting pulls out fiberglass filaments instead of cutting them cleanly, leaving rigid fiberglass burrs on the end face. During lamination, these hard burrs prop up the tape edge, forming tiny gaps between the adhesive surface and workpiece – blocking full contact and causing lifting.
If slitting causes delamination between the PTFE coating and fiberglass at edges, mismatched thermal expansion rates generate internal stress after heating, directly peeling edges away from substrates.
3. Serrated or notched edges – stress concentration
Visible serrations and notches trap air and prevent full surface contact after bonding. Even macroscopically flat edges with micro-unevenness experience uneven thermal expansion when heated, tearing the bonding interface and triggering cascading edge lifting.
4. Contamination from extruded adhesive – reduced edge tack
Severely oozed adhesive may re-adhere to the tape end, altering the chemical properties of the marginal adhesive layer. Trace oil stains transferred from blades also lower edge tackiness – all acting as lifting inducements.
Standard End Face Requirements – How to Prevent Oozing and Lifting
To suppress adhesive oozing and edge lifting fundamentally, the slitting end face must meet the following criteria:
1. Morphology – smooth and flush
Glass fibers cut cleanly without exposure.
Adhesive layer, substrate, and PTFE coating form an integrated flat section.
No glue stringing, adhesive shortage, or delamination.
2. Regularity – straight and uniform
Straight end face with minimal waviness and inclination.
Ensures uniform stress distribution when wound into rolls.
A smooth, intact, damage-free end face acts as a "seal" for tape edges. It locks the adhesive layer against creep migration and guarantees complete bonding capacity along every millimeter of the edge – eliminating oozing and lifting at the source.
Aokai PTFE uses precision slitting equipment with sharp blades and optimized angles to produce tape edges that are clean, smooth, and free of defects. If you are experiencing edge oozing or lifting with other tapes, slitting quality may be the cause. Contact us to discuss your application.
If you wish to learn more about detailed specifications, application scenarios and customized solutions for our full product range, including PTFE high-temperature fabrics, PTFE high-temperature tapes, PTFE mesh conveyor belts, seamless bonding machine belts, single-sided PTFE cloth, high-temperature resistant conveyor belts and high-temperature resistant fiberglass fabrics, please contact us:
