Adaptation of PE Blown Film Machine for Agricultural Film and Mulch Production
To adapt PE blown film machines to the production and processing of agricultural film and mulch, systematic adjustments shall be made in terms of equipment selection, raw material matching, process optimization, auxiliary system configuration and quality control, centering on the core properties of agricultural film and mulch such as thickness, uniformity, aging resistance and mechanical properties. The goal is to achieve efficient, stable and large-scale production. The specific adaptation strategies are as follows:
I. Clarification of Core Requirements for Agricultural Film and Mulch
Common requirements for agricultural film (greenhouse film, covering film) and mulch include: ultra-thin thickness (0.008–0.015mm for mulch, 0.012–0.025mm for agricultural film), width adaptation (1–2m for mulch, 3–10m for greenhouse film), thickness uniformity (tolerance ≤±5%), aging resistance (outdoor service life: 3–12 months), and puncture resistance (to withstand soil friction and crop root penetration). These requirements define the adaptation direction of blown film machines.
II. Equipment Selection and Adaptation of PE Blown Film Machine
1. Screw System: Matching Plasticization Requirements of Raw Materials
Agricultural film and mulch are mainly made of LDPE or LLDPE. Suitable screw parameters are required:
Length-diameter ratio: 25:1 to 30:1 is recommended to ensure sufficient plasticization without excessive material degradation (LDPE plasticization temperature: 150–180℃; LLDPE: 160–190℃).
Screw structure: Gradient screw with increased compression ratio (3:1–4:1) to improve melting efficiency. For filled materials such as calcium carbonate, an extended mixing section is required to ensure even dispersion of fillers.
2. Die Head System: Ensuring Width and Thickness Uniformity
Die head type: Rotary die head is preferred to avoid bubble swing and reduce thickness deviation. Die head diameter shall be calculated according to target width (Blow-up Ratio = Film Width / (π × Die Head Diameter); blow-up ratio: 2–3 for mulch, 3–5 for agricultural film).
Die gap: Adjusted according to film thickness demand (e.g., 0.5–0.8mm die gap for 0.01mm mulch) to guarantee uniform discharge.
3. Cooling System: Rapid Stabilization of Film Bubble
Ultra-thin agricultural film and mulch require rapid cooling to prevent adhesion:
Double-layer high-efficiency air ring: Outer layer cools the film bubble surface; inner layer stabilizes bubble shape with adjustable uniform air volume.
Optional water cooling system: For ultra-thin film, water ring cooling can be added to enhance cooling efficiency and reduce film bubble shrinkage.
III. Adaptation and Adjustment of Raw Materials and Additives
Functional additives are required for agricultural film and mulch, and the blown film machine shall adapt to the processing characteristics of blended materials:
Raw material blending: Use high-speed mixer to blend PE resin with anti-aging agent (UV-531), antioxidant (1010), antiblocking agent (silica) and fillers such as calcium carbonate (blending temperature: 80–100℃, time: 10–15min).
Drying treatment: Dehumidify raw materials with moisture content over 0.1% via dehumidifying dryer at 70–80℃ to avoid bubble formation on film.
Melt index control: Select LDPE with MI 1–5g/10min or LLDPE with MI 2–8g/10min to ensure stable extrusion.
IV. Optimization and Configuration of Process Parameters
1. Temperature Control
Barrel temperature: Gradually increased from feeding section to head (feeding: 120–140℃, compression: 150–170℃, metering: 160–180℃, head: 170–190℃).
Die head temperature: Slightly higher than barrel metering section (180–200℃) to ensure smooth discharge without material accumulation.
2. Blow-up and Traction Parameters
Blow-up ratio: Adjusted according to mulch/agricultural film width.
Traction ratio: Ratio of traction speed to extrusion speed (3–5 for mulch, 5–8 for agricultural film), coordinated with blow-up ratio to avoid excessive stretching and deterioration of mechanical properties.
Tension control: Maintain stable winding tension at 0.5–1.5N to prevent wrinkling or loosening.
3. Cooling Air Volume
Adjust air volume according to film thickness: high air volume for rapid cooling of 0.01mm thin mulch; appropriately reduced air volume for 0.02mm agricultural film to ensure flat and wrinkle-free film bubble.
V. Supporting Configuration of Auxiliary Equipment
Online thickness gauge: Real-time film thickness monitoring with automatic feedback to adjust die gap or traction speed, ensuring thickness tolerance ≤±5%.
Winding machine: Double-station winder equipped with tension control and deviation correction device for neat rolling.
Waste recycling system: Crush edge trims and blend back into raw materials (proportion ≤15%) to reduce cost while maintaining product quality.
VI. Establishment of Quality Control System
Offline inspection: Regular testing on tensile strength (≥15MPa), elongation at break (≥300%), light transmittance (≥85% for agricultural film) and aging resistance (accelerated aging test ≥500h).
Process recording: Record parameters such as temperature, blow-up ratio and traction speed to build a process database for rapid formula and process adjustment.
Conclusion
The adaptation of PE blown film machines to agricultural film and mulch production shall be based on product core properties. Through coordinated optimization of equipment selection, raw material formulation, process parameters and auxiliary systems, products with uniform thickness and stable performance can be stably produced. Meanwhile, intelligent control such as PLC system and energy-saving design with variable-frequency motors can further improve production efficiency and economic benefits, meeting the modern agriculture demand for high-quality agricultural film and mulch.
