From ‘Stick’ to ‘Slip’: How Viscoelastic Design Tunes Silicone Adhesives and Release Liners

Why this matters in personal care & consumer Goods

From feminine hygiene liners to wearable medical devices and protective films for touchscreens, silicone coatings enable controlled release when needed and reliable adhesion when required. These behaviours emerge from the same viscoelastic fundamentals that can be measured, plotted and engineered.

The three silicone coating families

Release Coatings (RCs)

Pressure-Sensitive Adhesives (PSAs)

Soft Skin Adhesives (SSAs)

• Release Coatings (RCs): Ultra‑low surface‑energy layers applied to paper or film liners, enabling clean release for labels and hygiene product constructions.
• Pressure‑Sensitive Adhesives (PSAs): Silicone polymers blended with MQ resins for tack, peel and shear. Ideal where acrylates struggle, such as high temperatures or low‑energy substrates.
• Soft Skin Adhesives (SSAs): Lightly crosslinked silicone gels designed for uneven, moist or oily skin surfaces, enabling gentle removal for medical and consumer applications.

The viscoelastic window explained

The viscoelastic window uses four rheological measurements, G′ and G″ at low and high frequencies, to form a simple rectangle on a loss, storage plot. Its position effectively predicts adhesive behaviour:

• G′ (storage modulus): Rigidity or elasticity of the material.
• G″ (loss modulus): Energy dissipation or viscous behaviour.

Dahlquist Criterion: A low‑frequency G′ below ~3 × 10⁵ Pa indicates sufficient tackiness.

G′–G″ crossover line: Materials straddling this line tend to remove cleanly without cohesive failure.

In practice:

• RCs cluster in the high‑G′ / low‑G″ region.
• General‑purpose PSAs sit near the centre with balanced properties.
• SSAs lie at lower G′ and G″ values for easy bonding and gentle removal.

 

Your chemical toolbox for tuning performance

Structure of MQ resins and their role in tuning viscoelastic behaviour.

 

Because RCs, PSAs and SSAs share similar silicone chemistry, a formulation’s viscoelastic window can be shifted by adjusting:

• Molecular weight: Higher MW increases rigidity (higher G′).
• Crosslinking degree: More crosslinks strengthen the network.
• Coatweight: Defines flow and anchoring (RC: 0.1–2 μm, PSA: 10–50 μm, SSA: 100–200 μm).
• MQ resins: The most precise lever for adjusting tack, peel and shear, and for controlling release tightness in RCs.

 

Pairing adhesives and liners

Silicone PSAs can chemically interact with standard silicone release coatings, causing unstable release. This is why fluorosilicone release liners are typically preferred for silicone PSAs. SSAs often release well from non‑siliconised or embossed films; hybrid SSAs may require siliconised or fluorosilicone liners.

 

What this means for brands and converters

• Design with the viscoelastic window: Define realistic bonding/debonding conditions and match them.
• Prioritise MQ resins over coatweight changes: They offer finer performance control.
• Match liner chemistry to adhesive chemistry: Reduces waste, improves consistency.

 

 

FAQs

What is the viscoelastic window?

A rectangle on a loss–storage plot using G′ and G″ at low and high frequencies.

How do MQ resins affect performance?

They increase cohesion and allow precise tuning of tack, peel and shear.

Why use fluorosilicone liners?

They prevent chemical interaction with silicone PSAs, ensuring stable release.

Where do SSAs fit?

In wound care, surgical tapes, scar treatment and wearable devices.

What is the Dahlquist criterion?

A tackiness threshold below ~3 × 10⁵ Pa low‑frequency G′.