2. Key Performance Characteristics
Stiffness (Primary Advantage)
Stiffness is measured via industry-standard tests such as the Taber Stiffness Test (ASTM D6433) or 4-point Bending Stiffness Test. For these laminated grey boards:
1.0mm board: Typical stiffness range (machine direction, MD): 80–120 mN·m; cross direction (CD): 40–70 mN·m
1.5mm board: MD: 180–250 mN·m; CD: 90–130 mN·m
2.0mm board: MD: 300–400 mN·m; CD: 150–220 mN·m
This stiffness level ensures the board does not deform when holding lightweight to medium-weight items (e.g., cosmetics, small electronics) and withstands die-cutting, folding, or gluing processes without cracking.
Thickness Consistency
Unlike single-layer grey boards, the laminated structure guarantees ±0.05mm thickness tolerance across the entire board surface. This is critical for mass production (e.g., box making), as uneven thickness would cause misalignment during die-cutting or poor adhesion in lamination.
Surface Smoothness & Printability
The laminated surface undergoes calendaring (a pressing process with heated rollers), resulting in a smooth, uniform texture with low surface roughness (measured as ≤5 μm via profilometer). This allows for excellent ink adhesion, making it suitable for various printing techniques:
Offset printing (for high-resolution graphics on luxury packaging)
Flexographic printing (for fast, cost-effective branding)
Digital printing (for small-batch, customized designs)
Moisture Resistance
While not fully waterproof, the laminated structure reduces moisture absorption compared to standard grey board. The board typically has a moisture content of 8–12% (controlled during production) and a water absorption rate (Cobb test, 30 seconds) of ≤20 g/m². This prevents swelling or softening in moderate humidity environments (e.g., retail stores, warehouses).
Eco-Friendliness
Most laminated grey boards are made from 70–90% recycled pulp, meeting global sustainability standards (e.g., FSC certification, EU Ecolabel). They are fully recyclable and biodegradable, aligning with the packaging industry's shift toward circular economy practices.
3. Thickness-Specific Application Scenarios
The three thicknesses cater to distinct end-use needs, as stiffness and thickness directly correlate with the board's ability to support weight and maintain structure:
| Thickness | Key Stiffness Feature | Typical Applications |
|---|---|---|
| 1.0mm | Lightweight yet rigid; easy to fold and die-cut | - Inner liners for gift boxes, shoe boxes - Card inserts for cosmetics (e.g., lipstick holders) - Small packaging for stationery (e.g., notebook covers, pencil cases) - Backing boards for greeting cards or photo frames |
| 1.5mm | Balanced stiffness and flexibility; suitable for semi-structural packaging | - Outer shells for small electronics (e.g., wireless earbud boxes) - Luxury packaging for skincare samples or perfume miniatures - Hardcover book covers (thin-format books) - Display stands for small retail products (e.g., candy, small toys) |
| 2.0mm | High stiffness; excellent load-bearing capacity | - Heavy-duty gift boxes (e.g., wine boxes, jewelry boxes with multiple layers) - Outer packaging for tools or small hardware (e.g., screwdriver sets) - Thick display shelves for retail (e.g., cosmetic counter displays) - Industrial separators (e.g., layers for glassware or fragile parts during shipping) |
4. Production Process Overview
The manufacturing of high-stiffness laminated grey board follows a precise, multi-step workflow to ensure consistency and performance:
Pulp Preparation: Recycled/virgin pulp is mixed with water, additives (e.g., starch for bonding, talc for smoothness), and dyes (to achieve the grey color) to form a uniform pulp slurry.
Layer Formation: The slurry is deposited onto a continuous wire mesh (Fourdrinier machine) to form thin, wet paper layers (each 0.1–0.2mm thick). Multiple layers are stacked to reach the target thickness (e.g., 5 layers for 1.0mm, 7–8 layers for 2.0mm).
Lamination & Pressing: The stacked wet layers are passed through a series of heated press rollers (temperature: 120–150°C; pressure: 15–25 MPa) to bond them into a single board. This step eliminates air gaps and enhances interlayer adhesion-critical for stiffness.
Drying: The laminated board is dried in a tunnel dryer (temperature: 80–100°C) to reduce moisture content to 8–12%, preventing warping.
Calendaring: The dried board is run through calendaring rollers to smooth the surface, improve printability, and calibrate thickness to the exact 1.0mm/1.5mm/2.0mm specification.
Quality Testing: Random samples are tested for stiffness, thickness tolerance, moisture content, and tensile strength to meet industry standards (e.g., ISO 2441 for paperboard thickness, ISO 5628 for stiffness).
5. Industry Standards & Quality Certifications
To ensure reliability, reputable manufacturers adhere to global standards and certifications:
ISO Standards: ISO 2441 (thickness), ISO 5628 (stiffness), ISO 187 (moisture content), ISO 3783 (printability).
Sustainability Certifications:
FSC (Forest Stewardship Council): Ensures pulp comes from responsibly managed forests.
EU Ecolabel: Validates eco-friendliness (low carbon footprint, recyclability).
SGS/Intertek Testing: Third-party verification of performance (stiffness, durability) and safety (no harmful chemicals like heavy metals).
Packaging-Specific Standards: ASTM D4727 (test method for board stiffness in packaging) and GB/T 13024 (Chinese national standard for grey board).
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