压力敏感胶带：丙烯酸与橡胶基胶粘剂对比

Introduction to PSA chemistry

Pressure-sensitive adhesives (PSAs) are viscoelastic materials that exhibit tack at room temperature with the application of slight pressure. They are indispensable in tape and label applications, where bond initiation, handling strength, and long-term adhesion are critical. Two dominant chemistries are acrylic and rubber-based systems. Acrylic PSAs are synthesized via emulsion or solvent routes, offering superior temperature resistance, UV stability, and clean peel behavior. Rubber-based PSAs, typically natural rubber, styrene-butadiene rubber (SBR), or butadiene rubber, provide high initial tack, low modulus, and excellent adhesion to low-energy surfaces at a lower cost. The choice between these chemistries hinges on service conditions, substrate energy, processing method, and regulatory constraints. This article dissects their molecular architecture, formulation levers, and empirical performance data to guide formulators and procurement engineers in selecting the optimal system.

Molecular architecture and raw materials

Acrylic-based PSAs

Acrylic PSAs are primarily free-radical copolymers of vinyl monomers such as acrylic acid (AA), 2-ethylhexyl acrylate (2-EHA), methyl methacrylate (MMA), and butyl acrylate (BA). The comonomer distribution governs glass transition temperature (Tg), polarity, and tack. Typical acrylic formulations include:

Acrylic acid (5–15 mol%): enhances polarity, improves adhesion to polar substrates, and enables ionic crosslinking.
2-Ethylhexyl acrylate (30–60 mol%): lowers Tg, increases flexibility, and improves low-temperature performance.
Methyl methacrylate (10–30 mol%): increases rigidity and heat resistance.
Butyl acrylate (10–30 mol%): balances tack and cohesion.

Polymerization is conducted via emulsion (surfactant-stabilized) or solution processes. Emulsion routes favor low-VOC and safety, while solvent systems allow precise molecular weight control. Post-polymerization modifications such as hydrolysis of acrylic acid units to carboxylate groups enable amine or zinc crosslinking, enhancing heat resistance and cohesion.

Rubber-based PSAs

Rubber-based PSAs rely on natural rubber or synthetic elastomers (SBR, polyisoprene, butadiene rubber). Their structure is less uniform, with a broad molecular weight distribution and inherent crystalline domains in SBR that induce physical crosslinking via entanglements and microphase separation. Key components include:

Natural rubber (30–70 phr): provides high initial tack and elongation.
Paraffin oil or aromatic oil (10–30 phr): plasticizes the matrix, lowering modulus and enhancing wet-out.
Resins (e.g., C5/C9 rosin, hydrogenated rosin): act as tackifiers and polarity adjusters.
Antioxidants and antiozonants (0.5–2 phr): protect against thermal and oxidative degradation.

SBR offers better abrasion resistance and lower cost, while natural rubber delivers superior cohesive strength and high-speed application performance.

Formulation levers and dosage ranges

Acrylic PSA formulation guidelines

Acrylic acid: 5–15 mol%. Below 5 mol%, polarity is insufficient for polar substrates; above 15 mol%, tack drops and film becomes brittle.
2-EHA: 30–60 mol%. Optimizes flexibility and low-temperature adhesion.
MMA: 10–30 mol%. Controls rigidity and heat resistance.
Butyl acrylate: 10–30 mol%. Enhances cohesion and peel strength.
Photoinitiator (if UV-cured): 0.5–2 wt% based on total resin.
Crosslinker (e.g., triethylenetetramine or ZnO): 0.5–3 phr for post-crosslinkable systems.
Rheology modifiers: fumed silica (0.3–1.5 phr) to control viscosity and prevent settling.

Rubber-based PSA formulation guidelines

Base elastomer: 40–80 phr (depending on target modulus).
Plasticizer oil: 10–30 phr to reduce glass transition and improve wet-out.
Tackifier resin: 5–20 phr (C5/C9 rosin or hydrogenated rosin grades).
Fillers (e.g., CaCO3): 0–30 phr for cost control and rheology; note that high filler reduces tack.
Stabilizers: antioxidant (0.1–1 phr), antiozonant (0.2–1 phr).
Optional viscosity modifiers: asfotase or metal soaps for emulsion grades.

Performance comparison in tape and label applications

Property	Acrylic PSA	Rubber-based PSA
Initial tack (loop test, 25°C)	Moderate to high (varies with formulation)	Very high; excels on low-energy surfaces (PE, PP)
Shear strength (180°, stainless, 25°C)	10–30 minutes	5–15 minutes (often lower)
Temperature resistance	Continuous: 90–120°C; intermittent: 140–160°C	Continuous: 70–90°C; intermittent: 110–130°C
UV resistance	Excellent (minimal yellowing)	Poor (yellowing, depolymerization)
Cohesion (room temp, 24 h)	High; minimal deformation under load	Moderate to low; prone to flow at elevated temps
Application speed	Suitable for high-speed roll-to-roll	Excellent for high-speed application due to low modulus
Substrate compatibility	Broad; strong on polar surfaces (PET, glass, paper)	Broad; superior on non-polar, low-energy substrates
Aging (humidity, 6 months)	Low plasticization; stable	Moderate swelling in high humidity; plasticization possible
Environmental compliance	Generally RoHS/REACH compliant; halogen-free options available	Natural rubber may carry allergen concerns; SBR preferred in sensitive applications

Performance under varying conditions

Temperature

Acrylic PSAs retain cohesion and adhesion up to 120°C continuous use due to their higher Tg (typically 30–60°C). Formulators can raise Tg by increasing MMA content or introducing rigid monomers. Rubber-based systems soften rapidly above 90°C, leading to loss of peel strength and increased flow. For label applications exposed to oven environments (e.g., food packaging pasteurization at 85–95°C), rubber-based PSAs may suffice for short durations, but acrylics are preferred for >100°C intermittent exposure.

UV exposure

Acrylics, particularly those with aliphatic structures, show minimal photo-oxidation. Accelerated UV testing (ASTM G155) shows negligible change in tack after 500–1000 kJ/m² exposure. Rubber-based PSAs exhibit yellowing and tack loss beyond 200–300 kJ/m² due to double bond scission and crosslinking. For outdoor tapes, acrylics are the default choice.

Humidity and moisture

Rubber-based adhesives are more hygroscopic; plasticizer migration and water uptake can plasticize the matrix, reducing cohesive strength. At >60% RH, rubber PSAs may show up to 30% reduction in peel adhesion after 7 days. Acrylics are less permeable to moisture, maintaining performance in humid environments. Hydrolyzable crosslinks in acrylics (e.g., ester groups) can be engineered to improve moisture resistance.

Substrate energy and roughness

On low-energy substrates (surface energy <30 mN/m, e.g., polyethylene, polypropylene), rubber-based PSAs excel due to low modulus and high wetting. Acrylics with tailored surface polarity (via acrylic acid) can achieve strong bonds on the same substrates, but require optimized viscoelastic balance. On rough surfaces, rubber’s higher elongation (up to 500–800%) provides conformability, whereas acrylics may fracture if elongation at break is below 100%.

Processing considerations

Application method: Rubber-based PSAs are favored in high-speed slot-die and roll-to-roll coating due to low viscosity and high solids. Acrylic emulsions can be formulated for knife or slot-die coating but may require defoamers and careful rheology control.
Curing: Acrylics can be solvent- or water-based; drying kinetics must match line speed. UV-curable acrylics enable instant tack and high throughput.
Storage stability: Rubber formulations may phase-separate over time; antioxidants and proper milling are essential. Acrylic emulsions are generally more stable, with shelf lives exceeding 12 months.
Dielectric and thermal conductivity: Acrylics can be engineered with fillers for dissipative applications, whereas pure rubber systems are more insulating.

Practical formulation adjustments

To enhance peel strength on PET, increase acrylic acid to 10–12 mol% and incorporate a soft acrylate (2-EHA 40–50 mol%). For high-temperature tape, raise MMA to 25–30 mol% and introduce a small amount of aromatic methacrylate (2–5 mol%) for rigidity. To improve wet-out on PP without yellowing, use a hydrogenated rosin tackifier (5–10 phr) in a rubber-based system with 20 phr SBR and 20 phr oil. For low-odor, water-based label adhesives, an acrylic dispersion with 8 mol% acrylic acid, 40 mol% 2-EHA, and 0.8 phr fumed silica is a robust starting point.

Summary

Acrylic and rubber-based PSAs serve distinct roles in tape and label manufacturing. Acrylic systems provide superior thermal and UV stability, controlled polarity, and consistency, making them ideal for high-performance and outdoor applications. Rubber-based adhesives deliver unmatched initial tack, low-temperature flexibility, and cost efficiency, suitable for short-life, high-speed applications on challenging substrates. Formulators must align monomer selection, crosslink strategy, and rheology modifiers with end-use conditions. Procurement engineers should weigh raw material costs, regulatory limits, and processing compatibility to optimize performance and total cost of ownership.