What Is PE Film in Cement Packaging?
PE (polyethylene) film is a thin plastic sheet used inside or on the surface of cement bags to create a moisture barrier that prevents cement from absorbing humidity. Cement is highly hygroscopic — it absorbs water from the air and begins to harden, making it unusable.
PE film is used in two main ways:
- As a liner — An inner PE bag inserted inside a PP woven or paper outer bag
- As a lamination layer — PE film bonded directly to paper or PP fabric surface
Why Moisture Protection Matters
Unprotected cement loses 2–5% of its usable weight to moisture absorption in humid climates. For a factory producing 1 million bags/month, this represents:
- $50,000–$250,000/month in cement spoilage
- Customer complaints about hardened, unusable cement
- Brand reputation damage in competitive markets
PE film essentially eliminates moisture absorption during transport and storage.
PE Film — Three Integration Methods
Types of PE Film for Cement Bags
By Application
| Type | Application | Thickness | Cost per Bag |
|---|---|---|---|
| Liner Film | Separate bag inside outer bag | 50–100 micron | $0.02–$0.05 |
| Lamination Film | Bonded to PP or paper surface | 15–40 micron | $0.01–$0.03 |
| FFS Film | Forms the entire bag (FFS systems) | 80–150 micron | $0.05–$0.08 |
| Tubular Film | Multi-layer paper bag inner layer | 20–40 micron | $0.01–$0.02 |
By PE Type
- LDPE (Low-Density) — Flexible, good sealing, standard for liners ($1.10–$1.60/kg)
- LLDPE (Linear Low-Density) — Better puncture resistance, used in FFS ($1.20–$1.70/kg)
- HDPE (High-Density) — Stiffer, better moisture barrier, used for rigid liners ($1.00–$1.40/kg)
- mLLDPE (Metallocene) — Premium performance, best sealing at low temperatures ($1.50–$2.00/kg)
By Structure
- Mono-Layer — Single PE layer, simplest, most common
- Co-Extruded (2–3 layers) — Multiple PE types combined for optimized properties
- Micro-Perforated — Tiny holes for air escape during filling (paper valve sacks)
Key Specifications
| Property | Liner Film | Lamination Film | FFS Film |
|---|---|---|---|
| Thickness | 50–100 µm | 15–40 µm | 80–150 µm |
| MVTR* | <5 g/m²/day | <8 g/m²/day | <3 g/m²/day |
| Seal Strength | 20–40 N/25mm | N/A (bonded) | 30–60 N/25mm |
| Dart Impact | >200g | N/A | >300g |
| Elongation | 300–600% | 200–400% | 400–700% |
*MVTR = Moisture Vapor Transmission Rate (lower is better)
PE Film Integration in Different Bag Types
Paper Valve Sack with PE Layer
PE film is inserted as one of the layers during tube formation on the tuber machine:
Layer 1 (outer): 80 GSM kraft paper
Layer 2: 70 GSM kraft paper
Layer 3: 20-30 µm PE film ← moisture barrier
Layer 4 (inner): 70 GSM kraft paperThis is the approach used by 5-layer tuber machines like the Joyda JY-T500.
PP Woven Bag with PE Liner
A separate PE bag is inserted inside the PP woven bag:
- Liner is pre-made on tubing/sealing machine
- Inserted by hand or by auto liner insertion machine (like Five Fingers FF-LP45)
- Adds $0.02–$0.05 per bag in material cost
PP Woven Bag with PE Lamination
PE film is bonded directly to PP woven fabric:
- Applied by extrusion lamination machine (LAM-1200 type)
- Creates permanent moisture barrier layer
- Does not affect bag filling or closing operations
- Adds $0.01–$0.03 per bag
Cost-Benefit Analysis
PE Film vs Cement Loss
For a factory producing 1,000,000 bags/month in a humid climate:
| Scenario | Monthly Cost | Annual Cost |
|---|---|---|
| No PE protection (2% cement loss) | $100,000 in spoiled cement | $1,200,000 |
| PE lamination ($0.02/bag) | $20,000 | $240,000 |
| PE liner ($0.04/bag) | $40,000 | $480,000 |
| Savings with lamination | $80,000/month | $960,000/year |
The investment in PE film pays for itself within the first month.
Quality Testing
Essential quality tests for PE film in cement bags:
- MVTR Test — Measures moisture vapor passing through film (ASTM E96)
- Dart Impact Test — Measures puncture resistance (ASTM D1709)
- Seal Strength — Measures heat-seal bond strength (ASTM F88)
- Thickness Uniformity — Film gauge variation should be within ±5%
- Pin-Hole Test — Checks for microscopic holes that allow moisture passage
Supplier Selection
Key Factors
- Film quality consistency — Gauge variation, optical clarity, seal performance
- Minimum order quantity — Typically 5–10 tons per order
- Lead time — 2–4 weeks for standard grades
- Technical support — Film selection guidance, troubleshooting
- Price stability — PE prices fluctuate with oil prices
Major PE Film Producers
- Berry Global (USA)
- Sealed Air (USA)
- Coveris (Europe)
- Cosmo Films (India)
- Uflex (India)
- Numerous Chinese and Southeast Asian converters
Environmental Considerations
- Recyclable — PE is type 2 (HDPE) or type 4 (LDPE), widely recyclable
- Recycling challenge — PE laminated on paper/PP creates multi-material waste
- Emerging alternatives — Bio-PE from sugarcane, water-based barrier coatings
- Market trend — Growing demand for mono-material solutions (all-PP or all-PE) for easier recycling
Frequently Asked Questions
Which is better — PE liner or PE lamination? For most applications, PE lamination is more cost-effective ($0.01–$0.03/bag vs $0.02–$0.05 for liners), requires less labor, and doesn’t add a separate production step. Liners provide slightly better moisture protection and are easier to implement without a lamination machine.
What thickness PE film do I need for cement bags? For lamination: 15–25 micron is sufficient for standard protection. For liners: 50–80 micron provides good balance of protection and cost. For FFS bags: 100–150 micron is standard.
Does PE film affect bag filling speed? PE liners can slightly reduce filling speed (5–10%) due to reduced air permeability. PE lamination on paper bags may require micro-perforation to allow air escape during valve filling.
How is PE film affected by temperature? Standard LDPE remains flexible from -50°C to +80°C. In hot climates (>40°C), stored PE film rolls should be kept shaded. Below -20°C, film can become brittle and more prone to cracking.
Learn about machines that process PE film in our FFS Machine Guide or Lamination Machine Guide.