- Core Performance Requirements for Transparent Materials in Carton Sealing Labels
The application environment of carton sealing labels demands more than just transparency — the material must deliver multidimensional performance. Throughout logistics processes, labels must endure high-speed application on packaging lines, compression and friction during transport, and fluctuations in temperature and humidity in storage. In specific scenarios like cold chain logistics or outdoor shipping, labels also face extreme conditions. Therefore, the material must meet these core criteria:
Transparency and Clarity:
Labels must clearly display printed information such as serial numbers, QR codes, and warnings. Key indicators include:
Light transmittance: Should be ≥85% to ensure readability.
Haze: Should be ≤3%; excessive haze can scatter light and make QR codes unscannable, reducing logistics efficiency.
Mechanical Strength:
To resist damage and tampering, the material must:
Have tensile strength ≥25MPa (e.g., BOPP achieves up to 200MPa).
Abrasion resistance: Withstand ≥500 rubs (per ASTM D3359) to protect printed data.
Tear strength: Balanced for tamper evidence — not too weak to tear accidentally, nor too strong to damage the package during opening.
Environmental Resistance:
Materials must remain stable under:
Temperature from -20°C to 60°C, resisting brittleness or softening.
Humidity up to 90% without absorbing moisture or wrinkling.
Chemical resistance: Stable when exposed to water, oil, or disinfectants like alcohol.
UV resistance: Especially for outdoor transport like sea freight to prevent aging and brittleness.
Adhesion Stability:
Materials should adhere well to various substrates like cardboard, wood, or plastic crates:
Surface tension ≥38 dyn/cm (achieved via corona treatment) for adhesive bonding of ≥5N/25mm.
Heat shrinkage ≤1% after 24 hours at 60°C to avoid edge curling that obscures information.
- Performance Comparison of Mainstream Transparent Materials
BOPP Film: The Optimal Solution for General Use
Transparency: 92% light transmittance, 1% haze — ideal for clear QR code visibility.
Mechanical Strength: 200MPa tensile strength; excellent abrasion resistance and clean tear for tamper evidence.
Environmental Stability: Performs well from -40°C to 120°C, with <0.5% shrinkage.
Cost-effective: About 30% cheaper than PET, suitable for mass logistics operations.
Limitation: Slightly weaker impact resistance at low temperatures, but this can be improved with toughening agents like POE. Suitable for nearly all but extreme cold routes (e.g., Siberian routes).
PET Film: High-Performance Material for Extreme Conditions
Temperature range: Stable from -70°C to 150°C — ideal for cold chain logistics (fresh produce, pharmaceuticals) and tropical transport.
Tear Resistance: 250MPa tensile strength; superior puncture resistance, suitable for heavy-duty packaging with metal parts.
Chemical Stability: Resistant to acids, alkalis, and oils, perfect for chemical product packaging.
Downside: 40% higher cost than BOPP, making it more suitable for high-value or regulated logistics like pharma GSP-certified transport or international shipping.
PVC and PE Films: Limited Use in Specific Scenarios
PVC: Good transparency and low cost, but poor heat resistance (softens above 60°C) and absorbs moisture (haze rises beyond 80% humidity), fit only for short-distance, low-humidity transport.
