3M 9578 Splicing Tape is a single-coated polyester film tape identified by the product code 9578 and manufactured with a crosslinked silicone pressure-sensitive adhesive. The tape is supplied in roll form, typically slit to widths between 25 mm and 1,200 mm, and is used for web splicing in coating, laminating, and converting operations where the substrate itself is a silicone-coated release liner or where the splice must pass through a high-temperature drying tunnel. The backing is a transparent blue poly(ethylene terephthalate) film with a nominal total thickness of 0.064 mm. Because the adhesive is silicone-based, the tape can form a bond to silicone release surfaces that would reject many acrylic or rubber adhesives. This property is the primary reason for specification in release-liner manufacturing and in pressure-sensitive adhesive coating lines where roll changes are performed without stopping the process.

The polyester backing contributes to dimensional stability during web acceleration and deceleration. The tape is typically converted into roll lengths determined by the converting operation; master rolls may be supplied for in-house slitting. The color is not merely cosmetic: the blue tint provides visual contrast on white or coated release liners and allows splice detection by optical sensors on some web inspection systems. The product is not grouped with general-purpose acrylic splicing tapes. Acrylic tapes frequently show higher room-temperature peel on stainless steel but lower wetting and low-surface-energy adhesion on silicone-coated papers and films. The silicone adhesive of 3M 9578 is crosslinked to limit cohesive failure at elevated temperature, but it remains pressure-sensitive at ambient conditions.

Why does silicone adhesive chemistry change splicing performance on release liners?

Silicone release liners present a low-surface-energy surface that is deliberately designed to prevent adhesion. Conventional acrylic adhesives may leave the liner surface with minimal residue but also fail to develop enough peel strength for a reliable flying splice because the adhesive cannot wet the surface. The silicone adhesive on 3M 9578 has a higher affinity for methyl-terminated silicone surfaces, allowing the splice to form a load-bearing bond without corona treatment or solvent priming. Peel adhesion to stainless steel is not a direct predictor of adhesion to a silicone liner; the relevant property is the interaction between the silicone adhesive and the silicone release coating. Published data for adhesion to specific release coatings is limited; the manufacturer provides stainless steel values as a quality-control reference. The typical peel adhesion to stainless steel is 8.3 N/25 mm when tested in accordance with ASTM D3330. Tensile strength at break is typically 525 N/100 mm with elongation at break of 100% when tested in accordance with ASTM D3759.

The crosslinked silicone adhesive also reduces cohesive splitting at high temperature. In a splice, the adhesive must resist both peel forces at the trailing edge and shear forces along the overlap. If the adhesive is too soft, the splice can creep under sustained unwind tension; if it is too hard, it cannot wet the release surface. The balance is achieved by a silicone gum network with controlled crosslink density. The result is a high-shear splicing system that maintains lap strength in ovens where acrylic adhesives begin to flow. The adhesive builds shear strength rapidly after the application of pressure. On a splice station, a nip roller at 2–4 bar reduces trapped air and improves contact. Without mechanical pressure, hand-applied tape may show inconsistent edge adhesion, particularly on dense clay-coated paper or textured release liners. The backing is sufficiently thin to pass through narrow gap coating heads, but the lap edge still represents a caliper step that can mark the web in some calender stacks or reverse roll coaters.

On high-speed converting lines, the splice is usually made at the unwind station. The outgoing roll is slowed or the splice table is engaged, and the new roll is attached with a single strip of tape across the web width. For webs up to 1,000 mm, a continuous strip with 50 mm overlap is common. For wider webs, two strips with staggered edges prevent a continuous caliper ridge from tracking into the winder. The tape should be applied to a clean, dry surface; isopropyl alcohol or heptane is used on coated papers to remove dust and excess release agent. The splice should pass through the first idler or dancer roller at reduced tension until the adhesive has developed full shear holding power. The lap edge of a polyester splicing tape can create a mechanical disturbance in precision coating processes. In reverse roll coaters or slot-die coating lines, the 0.064 mm caliper step can cause coating thickness variation if the splice passes through the coating gap. For that reason, the splice is typically placed in the roll before the edge of the coating head, or the process is designed to open the gap during splice passage. On a solventless silicone coating line, the splice need not be removed before coating if the adhesive transfer to the silicone matrix is tolerable, but the lap edge should be positioned parallel to the web edge to avoid diagonal stress concentration.

Splice failure in production is most often observed at the trailing edge of the overlap when tension is reapplied too quickly or when the splice is placed over a wrinkle in the new roll. A wrinkle under the tape creates a channel through which the adhesive cannot wet the substrate; the resulting loss of contact reduces shear area and can cause the splice to open at the unwind. The failure is not always adhesive failure; at high web speeds, the polyester backing itself can tear if the splice is not square to the web edge or if an idler roller is misaligned.

Nominal construction and test-method alignment

The values below are published typical values, not batch-specific specification limits. Lot-specific certificates of analysis should be consulted when a process qualification requires minimum or maximum values.

Dielectric strength and electrical insulation properties are not the primary function of this tape. If the spliced web passes through electrostatic pinning bars or corona treaters, the tape should not be considered an insulating barrier unless the user verifies the lot-specific dielectric performance. The polyester backing may withstand brief contact with a corona discharge, but repeated exposure can embrittle the film and reduce splice strength. Compliance documentation for the product is typically available under EU RoHS Directive 2011/65/EU, including delegated amendment EU 2015/863, and under REACH Regulation EC 1907/2006. The user should request the current regulatory statement from the manufacturer because formulations may vary by production plant and date.

When thermal cycling in release-liner ovens exposes the adhesive to 204°C

In coating tunnels operating between 150°C and 200°C, the polyester backing retains sufficient tensile strength to carry normal web loads, and the silicone adhesive does not soften or flow from the lap edge. The adhesive is crosslinked, and the backing begins to shrink only as the temperature approaches 204°C; above this point, splice distortion and edge lifting may occur. The tape is not recommended for continuous service in ovens designed for polyimide tapes. Intermittent excursions to 204°C are tolerated when the web tension is low and the oven residence time is short, but the splice should be inspected after the first pass. At elevated temperature, the polyester backing can lose dimensional stability if the web path includes rapid lateral shifts or high idler-roller drag. The backing elongation at break of 100% indicates that the film is oriented; at temperatures above the glass transition of PET, the orientation can relax and the tape may shrink. In a drying tunnel, this relaxation is usually less significant than the adhesive creep at the lap edge, but both mechanisms must be considered if the splice will remain in the oven for more than several minutes.

Silicone pressure-sensitive adhesives can transfer to adjacent surfaces when the splice is compressed under high temperature. This transfer is usually not a defect in silicone release liner production because the receiving surface is already silicone-functional. In applications where the spliced web later contacts an adhesive coating or an optically clear film, trace transfer must be evaluated by an adhesion loss test on the downstream product. Silicone contamination can reduce subsequent coating adhesion even when no visible residue is present.

Polyimide splicing tapes differ in upper use temperature, stiffness, and application window.

Acrylic splicing tapes are generally selected for high peel strength on polar substrates and lower material cost; however, their room-temperature advantage on steel does not translate to silicone release surfaces, and their shear strength falls as the adhesive softens at temperatures above 120°C to 150°C. Rubber-based tapes flow at even lower temperatures and can exude adhesive from the splice edge in drying ovens, causing web contamination. Polyimide splicing tapes provide a higher temperature rating, often above 260°C, but they have higher stiffness and are typically specified only when the process temperature or mechanical abuse exceeds the capability of polyester backings. Within the polyester silicone-adhesive class, 3M 9578 differs from thinner polyester tapes by providing higher tensile strength and more dimensional stability under web acceleration; it differs from thicker polyester tapes by introducing less caliper at the splice edge. The transparent blue backing allows visual registration of the splice through transparent films. The product is not a substitute for a permanent adhesive lamination; it is a temporary web-splicing tape with pressure-sensitive adhesion. It also differs from unsupported silicone adhesive transfer tapes because the polyester backing prevents the splice from stretching and necking under unwind tension.

Silicone transfer remains the primary boundary condition.

The tape is not formulated for direct food contact, pharmaceutical product contact, or medical device surfaces. It is not intended for use as electrical insulation unless a lot-specific dielectric withstand test is performed for the exact laminate construction. The silicone adhesive can interfere with subsequent painting, bonding, or coating operations; splice areas should be removed or isolated before those steps. On untreated polyolefin films, adhesion is low; corona treatment or an adhesion-promoting primer is required. Storage in high-humidity conditions above 60% relative humidity may increase the risk of adhesive edge oozing and liner curl; the product should be stored in the original roll packaging at 21°C and 50% relative humidity where possible.

The product should not be used to splice fluoropolymer release surfaces unless adhesion is verified on the actual substrate; silicone adhesives do not bond equally to all release chemistries. The adhesive is not chemically resistant to aggressive solvents such as ketones, chlorinated solvents, or certain esters; exposure to solvent vapors in coating tunnels should be assessed because swelling of the adhesive can reduce shear strength. Rolls should be acclimated to the application area before use to avoid condensation on the tape surface. In cold-room splicing, the adhesive should be conditioned to room temperature because low storage temperatures reduce tack and delay wet-out.