What Is a Release Liner? Logistics Labels

Overview and function

The release liner is a critical component in pressure-sensitive label systems and tapes used throughout logistics and supply chain operations. Its primary function is to carry and protect an adhesive-backed face stock (the label material) during manufacture, shipping, storage, and dispensing, then allow predictable separation (release) of the label from the liner at the point of application. In logistics contexts this includes shipping labels, barcode and pallet labels, inventory tags, and adhesive tapes where reliable peel performance, dimensional stability, and handling are essential.

Construction and common materials

Release liners typically consist of a base substrate and a release coating. Common base substrates include:

• Glassine paper — a smooth, translucent paper with good surface uniformity used in many label grades for its printability and low cost.
• Kraft paper (coated) — clay- or polyethylene-coated kraft for improved moisture resistance and runnability in high-speed converting.
• Film liners (PET, polycoated papers) — polyester (PET) films provide superior dimensional stability, high-speed dispensing, and are used where flatness and strength are required (e.g., thermal transfer labels, RFID inlays).

The release coating is most commonly silicone-based (neutral or acid-catalyzed silicones), applied to one or both sides of the liner to control the adhesive peel. Specialty chemistries (fluoropolymers, PTFE coatings) exist for extreme low-stick or high-temperature needs.

Key performance properties

Selection and specification of a release liner rely on measurable properties:

• Release force/peel value — measured in grams-force per inch or newtons per centimeter; indicates the force required to peel the label from the liner at a specified angle and speed.
• Initial vs. residual release — initial release is the peel force immediately after lamination; residual release describes how the peel changes after aging, storage, or environmental exposure.
• Sidedness — one-sided (single-sided silicone) or two-sided (double-lined) liners for laminates or for labels requiring a release surface on both sides.
• Dimensional stability — critical for registration during die-cutting and for thermal printing applications where shrinkage can cause jams or misprints.
• Surface energy and smoothness — impact adhesive wetting, print quality for direct printing on the liner, and die-cutting precision.

Types and common variants

Release liners are specified by substrate, coating, release level, and additional functional treatments. Typical variants used in logistics labeling include:

• Glassine with silicone coating — standard for many shipping and barcode labels; balances cost and performance.
• Polycoated kraft with silicone — used where moisture resistance and runnability on high-speed presses are required.
• PET film liners — employed for heavy-duty or high-speed dispensing, flatness-critical labels, and inlayed RFID labels where dimensional stability is paramount.
• Removable vs. permanent release liners — liners with low-release coatings designed for easy peel in removable label applications versus higher-release liners for permanent, long-life adhesives.
• Recyclable and compostable liners — emerging grades that use recyclable paper substrates and lower-impact coatings; compatibility with recycling streams is an active development area.

Testing and specification

Common test methods and specifications logistics teams and converters use include:

• Peel tests (180° or 90°, defined speed and dwell): determine release force. Test conditions must be documented (angle, speed, temperature, humidity).
• Aging studies: evaluate residual release after temperature cycling, humidity exposure, and long-term storage to prevent unexpected pick-off or adhesive transfer.
• Die-cut and matrix removal trials: ensure liners perform during high-speed converting and automatic dispensing equipment.
• Cohesion and tack testing of the adhesive in conjunction with the liner: the liner/adherent system must be validated, not each component in isolation.

Best practices for specification and implementation

To ensure reliable performance in logistics label applications, follow these guidelines:

• Specify liner/adherent systems together: the adhesive, face stock, and liner interact—the correct release profile depends on the entire stack.
• Define test conditions: use industry-standard peel tests and document angle, speed, and environmental conditions when specifying release values.
• Account for converting and dispensing speeds: high-speed labelers often need liners with lower variability and higher dimensional stability (PET or controlled paper grades).
• Plan for environmental extremes: select liners whose residual release remains stable across expected storage and application temperatures and humidities.
• Run trials: validate die-cutting, matrix stripping, printing, and applicator compatibility before large-scale production runs.

Common mistakes and failure modes

Poorly specified or tested release liners can lead to operational issues:

• Adhesive pick-off or transfer: insufficient release or changes after aging can cause adhesive to remain on the liner or transfer to the liner surface, jamming dispensers or causing label waste.
• Sticking in dispensers: liners with high static or poor slip can cause blocks or misfeeds in automatic applicators.
• Dimensional instability: shrinkage or stretching in the liner during processing leads to misregistration, print and die-cut issues, and scrap.
• Incompatible coatings: undesirable chemical interactions between adhesive and release coating may alter peel values or contaminate adhesive properties.
• Environmental non-compliance: assuming a paper liner is recyclable when it contains non-recyclable coatings; this increases downstream waste and regulatory risk.

Alternatives and emerging trends

While traditional silicone-coated liners remain dominant, several alternatives and trends affect logistics labeling:

• Linerless labels: eliminate release liners entirely, reducing waste and roll diameter. These require specialized adhesives and printers but are increasingly used for shipping labels and in retail where waste reduction is prioritized.
• Recyclable liners and coating innovations: developing water-dispersible or repulpable coatings and mono-material film liners to improve recyclability.
• High-performance film liners (PET): adoption in high-throughput warehouses for their runnability and stability.
• Lower-carbon silicone chemistries: process improvements and alternative release systems aimed at reducing environmental impact.

Practical examples in logistics

Examples illustrate how liner choice affects operations:

• Case 1: A 3PL using high-speed labelers switched from glassine to PET liners to eliminate web breaks and registration drift; uptime improved and scrap decreased despite higher liner cost.
• Case 2: A shipper experienced adhesive pick-off after labels were stored in a hot trailer; testing showed residual release had increased after heat aging, prompting a change to a liner with improved thermal stability.
• Case 3: A retailer piloted linerless thermal shipping labels to reduce packaging waste and roll handling; the pilot required new printers and adhesives but reduced waste and lowered transport costs per roll.

Procurement and lifecycle considerations

When specifying liners for logistics labeling, consider total cost of ownership: material cost, converting yield, downtime risk, recyclability, and roll logistics (roll diameter, core size). Work with converters and adhesive suppliers to qualify the entire label system. Maintain sample archives and run periodic requalification if supply sources or chemistries change.

Summary

The release liner is more than a disposable backing: it is an engineered component that affects label performance, converting efficiency, applicator reliability, and sustainability outcomes across the logistics chain. Correct liner selection, validated testing, and attention to operational conditions prevent common failures and optimize label performance in demanding warehouse and distribution environments.