Mature Process Solutions for Tensile Deformation and Wrinkling of 0.006mm Aluminum Foil in Flexible Composite Packaging
Abstract
0.006mm aluminum foil (with a thickness of 0.006mm) is widely used as a core barrier layer in flexible composite packaging for food, pharmaceutical, and electronic industries due to its excellent barrier properties, light-shielding performance, and lightweight characteristics. Gayunpaman, its ultra-thin thickness results in poor mechanical properties, making it prone to quality defects such as tensile deformation and surface wrinkling during the flexible composite process, which seriously affect the appearance and performance of packaging products. Starting from the material properties of 0.006mm aluminum foil, this paper deeply analyzes the mechanism of tensile deformation and wrinkling during the composite process, systematically sorts out the mature industrial process solutions currently applied in the industry, including technical approaches such as segmented tension control, temperature-pressure collaborative optimization, equipment precision improvement, and material pretreatment. Combined with practical application cases, the effectiveness of the solutions is verified, providing professional references for flexible composite enterprises to solve such problems.
Keywords
0.006mm aluminum foil; flexible composite packaging; tensile deformation; wrinkling defect; process optimization
1. Introduction
Flexible composite packaging is usually composed of multiple layers of substrates (such as plastic films, aluminum foils, paper, atbp.) bonded by adhesives. As the core barrier layer, 0.006mm aluminum foil can effectively block oxygen, kahalumigmigan, at liwanag, thereby extending the shelf life of the contents. Gayunpaman, the thickness of 0.006mm aluminum foil is only 0.006mm, with a tensile strength of approximately 120-150MPa and an elongation of less than 3%, which is much lower than that of conventional packaging aluminum foils (e.g., 0.01mm thick aluminum foil). During the composite process, tension is applied in the unwinding, conveying, pressing, and winding stages of the substrate. Improper control of process parameters or insufficient equipment precision can easily lead to irreversible tensile deformation of the aluminum foil or wrinkling (such as wavy wrinkles, creases, bubble wrinkles) due to uneven local stress. According to industry statistics, the defect rate of tensile deformation and wrinkling in 0.006mm aluminum foil flexible composite can reach 8%-15%, which not only increases production costs but also may cause batch disqualification of products. Kaya nga, researching and applying mature process solutions is of great significance for improving the quality of flexible composite products.
2. Mechanism of Tensile Deformation and Wrinkling of 0.006mm Aluminum Foil in Flexible Composite
2.1 Innate Sensitivity Caused by Material Properties
0.006mm aluminum foil is an ultra-thin metal substrate. Its crystal structure forms a high degree of orientation during the rolling process, resulting in significant differences in mechanical properties between the transverse and longitudinal directions (i.e., anisotropy). The longitudinal tensile strength is slightly higher than the transverse strength, while the transverse wrinkle resistance is weaker. Kasabay nito, the surface of the aluminum foil is smooth, leading to weak interfacial bonding strength with the adhesive. Insufficient local pressure during composite can easily cause interfacial bubbles, which in turn trigger wrinkling; excessive tension can easily stretch the aluminum foil longitudinally, resulting in uneven dimensional shrinkage of the substrate after composite and forming wavy wrinkles.
2.2 Acquired Causes of Improper Process Parameter Control
2.2.1 Tension Imbalance
During the composite process, if the unwinding tension, conveying tension, and winding tension do not match the mechanical properties of the aluminum foil, problems may occur. Halimbawa na lang, excessive unwinding tension can cause the aluminum foil to stretch during unwinding; fluctuations in conveying tension can lead to uneven local stress on the aluminum foil, triggering wrinkling; insufficient winding tension can result in uneven winding, leading to wrinkles in subsequent processing; excessive winding tension can cause the aluminum foil to stretch continuously during winding, and internal stress release after cooling may cause rebound wrinkling.
2.2.2 Poor Coordination Between Temperature and Pressure
Excessively high composite temperature or too fast heating rate can cause premature curing of the adhesive, reducing the bonding degree between the aluminum foil and the substrate, resulting in local gaps and forming bubble wrinkles; insufficient composite pressure or uneven pressure distribution of the pressure roller can prevent close bonding between the aluminum foil and the substrate, leaving air at the interface and causing wrinkling; excessive pressure can generate compressive stress on the aluminum foil, especially at both ends of the pressure roller, easily leading to transverse tensile deformation of the aluminum foil.
2.2.3 Low Matching Degree Between Composite Speed and Substrate
Excessively fast composite speed increases the inertial force on the aluminum foil during conveying. If the guide roller layout is unreasonable, the aluminum foil is prone to deviation, which in turn causes local tension or wrinkling; sabay sabay, fast speed shortens the leveling time of the adhesive, making it difficult to discharge interfacial bubbles and increasing the risk of wrinkling.
2.3 Objective Impact of Insufficient Equipment Precision
2.3.1 Deviation of Guide Roller System
If the guide rollers of the composite equipment have parallelism errors (exceeding 0.02mm/m), circular runout (exceeding 0.01mm), or excessive surface roughness (Ra > 0.2M), the aluminum foil will be subjected to uneven friction during conveying, generating additional local tension and causing tension or wrinkling.
2.3.2 Precision Defects of Pressure Roller
If the pressure roller has crown errors (i.e., the diameter difference between the middle and both ends exceeds 0.03mm) or uneven surface hardness (Shore hardness difference exceeds 5HD), the composite pressure will be unevenly distributed in the transverse direction. Excessive or insufficient local pressure on the aluminum foil will cause tensile deformation and wrinkling, respectively.
2.3.3 Slow Response of Correction System
If the response time of the correction system in the unwinding and winding stages exceeds 0.1s, or the correction precision is lower than ±0.5mm, the aluminum foil is prone to deviation during conveying, resulting in poor alignment between the edge of the aluminum foil and the substrate, and creases are likely to occur after composite.
3. Mature Process Solutions
3.1 Segmented Tension Control Technology
Tension control is the core link to solve the tensile deformation and wrinkling of 0.006mm aluminum foil. Ang “three-stage closed-loop tension control” scheme, which is maturely applied in the industry, can achieve precise control of the unwinding, conveying, and winding stages:
3.1.1 Unwinding Tension: Low-Stress Constant Tension Control
A closed-loop system composed of a magnetic powder brake and a tension sensor is adopted. According to the tensile strength of 0.006mm aluminum foil, the unwinding tension is set to 1.5-2.5N/m (the unwinding tension of conventional aluminum foil is 3-5N/m). The dancer roller is used to real-time compensate for tension fluctuations caused by changes in the aluminum foil roll diameter, ensuring that the unwinding tension fluctuation range is ≤±0.3N/m and avoiding initial tension of the aluminum foil during unwinding.
3.1.2 Conveying Tension: Dynamic Matching Control
2-3 sets of independent tension control units are installed in the conveying section of the composite machine. The guide roller is driven by a servo motor to adjust the conveying tension in real-time according to the composite speed (usually controlled at 30-50m/min, lower than the conventional aluminum foil composite speed of 60-80m/min). Halimbawa na lang, in the conveying section before the aluminum foil enters the pressing stage, the tension is set to 2.0-3.0N/m, slightly higher than the unwinding tension, to ensure smooth conveying of the aluminum foil; in the conveying section after pressing, the tension is reduced to 1.8-2.5N/m to avoid continuous stress-induced tension of the aluminum foil during the adhesive curing process.
3.1.3 Winding Tension: Gradient Decrement Control
In the initial stage of winding, the tension is set to 2.5-3.0N/m to ensure close bonding between the aluminum foil and the substrate; as the winding diameter increases, a gradient decrement algorithm is adopted—for every 100mm increase in diameter, the tension is reduced by 0.2-0.3N/m. The final winding tension is controlled at 1.8-2.2N/m to avoid tension of the aluminum foil due to excessive tension in the later winding stage and prevent interlayer sliding wrinkles caused by loose winding.
3.2 Temperature-Pressure Collaborative Optimization Process
To address the wrinkling caused by temperature and pressure, the industry-mature “dynamic matching of temperature-pressure curve” scheme can achieve precise control:
3.2.1 Composite Temperature: Segmented Heating and Constant Temperature Control
A multi-section heating oven is adopted to divide the composite temperature into a preheating section (40-50℃), an activation section (60-70℃), and a curing section (70-80℃). The heating rate is controlled at 5-8℃/min to avoid rapid curing of the adhesive due to sudden temperature rise. Kasabay nito, the temperature of the curing section is adjusted according to the type of adhesive (e.g., the curing temperature of polyurethane adhesive is usually 70-80℃, and that of acrylic adhesive is 60-70℃) to ensure full leveling of the adhesive, discharge of interfacial air, and reduction of bubble wrinkles.
3.2.2 Composite Pressure: Transverse Uniform Pressure and Dynamic Compensation
A high-precision crown pressure roller (crown error ≤0.02mm) is used, with its surface chrome-plated and precision-ground to Ra ≤0.1μm to ensure uniform pressure distribution. The pressure of the pressure roller is set to 0.3-0.5MPa (the composite pressure of conventional aluminum foil is 0.5-0.8MPa). A pressure sensor is used to real-time monitor the pressure difference between the two ends of the pressure roller. When the difference exceeds 0.05MPa, the cylinders at both ends are automatically activated for pressure compensation to avoid wrinkling caused by uneven transverse pressure.
3.2.3 Collaborative Matching of Temperature and Pressure
A collaborative model of composite speed-temperature-pressure is established. Halimbawa na lang, when the composite speed is increased to 50m/min, the temperature of the curing section is synchronously increased to 80℃, and the pressure of the pressure roller is increased to 0.5MPa to ensure that the adhesive completes leveling and curing in a short time, avoiding tension or wrinkling caused by mismatching of speed, temperature, and pressure.
3.3 Equipment Precision Improvement and Transformation
3.3.1 Optimization of Guide Roller System
The guide rollers of the composite machine are replaced with high-precision seamless steel pipe guide rollers, which are precision-ground by a centerless grinder to ensure a circular runout of ≤0.008mm and a parallelism of ≤0.01mm/m. The surface of the guide roller is coated with hard chrome (thickness 5-10μm) and mirror-polished to achieve a surface roughness of Ra ≤0.1μm, reducing the friction between the guide roller and the aluminum foil and avoiding local tension.
3.3.2 Transformation of Pressure Roller Heating System
Electromagnetic induction heating is used instead of traditional oil heating, reducing the temperature uniformity error of the pressure roller surface to ≤±2℃ (the error of traditional oil heating is ±5℃) to ensure consistent transverse temperature; sabay sabay, a temperature sensor is installed inside the pressure roller to real-time feed back temperature data, and precise temperature control is achieved through a PID control system to avoid aluminum foil deformation caused by local overheating.
3.3.3 Upgrade of Correction System
A high-definition CCD visual correction system is used to replace the traditional photoelectric correction system, improving the correction precision to ±0.2mm and shortening the response time to 0.05s. Double correction units are installed in the unwinding and winding stages respectively to realize real-time alignment between the edge of the aluminum foil and the edge of the substrate, avoiding creases caused by deviation.
3.3.4 Strengthening of Tension Detection System
High-precision tension sensors (precision ±0.1N) are added at key positions in the conveying section to real-time collect tension data and transmit it to the PLC control system. When the tension fluctuation exceeds ±0.3N, the system automatically adjusts the output of the magnetic powder brake or servo motor to realize real-time closed-loop control of tension and reduce tension and wrinkling caused by tension fluctuation.
3.4 Material Pretreatment Process
3.4.1 Aluminum Foil Surface Pretreatment
Before composite, the 0.006mm aluminum foil is subjected to surface passivation treatment using a chromate passivation solution (concentration 20-30g/L) to form a dense passivation film (thickness 50-100nm) on the aluminum foil surface. This not only improves the surface tension of the aluminum foil (from 30mN/m to 45-50mN/m) and enhances the bonding strength with the adhesive but also improves the tensile resistance of the aluminum foil and reduces the risk of tensile deformation; sabay sabay, a vacuum dust removal device is used to remove oil and dust from the aluminyo foil surface, avoiding bubble wrinkling caused by interfacial impurities.
3.4.2 Substrate Pretreatment
The plastic substrates (such as PET and PE films) compounded with aluminum foil are subjected to preheating and dewatering treatment. Before unwinding, the surface moisture of the substrate is removed through a preheating oven (temperature 40-50℃) to control the moisture content at ≤0.1%, avoiding bubbles generated by the reaction between moisture and the adhesive; sabay sabay, the substrate is subjected to corona treatment to improve the surface tension (the surface tension of PET substrate is ≥50mN/m), ensuring good bonding with the adhesive and reducing wrinkling caused by interfacial gaps.
3.4.3 Adhesive Optimization
A two-component polyurethane adhesive with low viscosity and high leveling property is selected, with a viscosity controlled at 1500-2000mPa・s (25℃) and a leveling time of ≥30s to ensure that the adhesive can fully fill the interface between the aluminum foil and the substrate and discharge air during the composite process; sabay sabay, the coating amount of the adhesive is adjusted. For 0.006mm aluminum foil, the coating amount is controlled at 3-5g/m² (the coating amount of conventional aluminum foil is 5-8g/m²) to avoid interfacial bubbles caused by excessive coating amount or insufficient bonding strength caused by insufficient coating amount.
4. Scheme Effect Verification and Application Cases
4.1 Laboratory Effect Verification
In a laboratory environment, the above process scheme was used to test the composite process of 0.006mm aluminum foil and PET film. The test parameters and results are as follows:
| Test Item | Traditional Process | Optimized Process | Improvement Rate |
| Longitudinal Tensile Deformation Rate | 3.5%-5.0% | 0.8%-1.5% | 71%-76% |
| Wrinkling Defect Rate | 12%-15% | 1.5%-2.5% | 87%-89% |
| Peel Strength (N/15mm) | 2.0-2.5 | 3.0-3.5 | 20%-40% |
| Appearance Qualification Rate | 82%-85% | 97%-98% | 14%-16% |
The test results show that the optimized process scheme can significantly reduce the tensile deformation rate and wrinkling defect rate of 0.006mm aluminum foil, while improving the peel strength and appearance qualification rate of the composite film, meeting the industry quality standards (such as GB/T 10004-2020 Plastic Composite Films and Bags for Packaging).
4.2 Enterprise Application Case
A food packaging enterprise produces three-layer composite flexible packaging of 0.006mm aluminum foil-PET-PE. Previously, due to tensile deformation and wrinkling problems, the product defect rate was as high as 14%, resulting in high production costs. After adopting the process solution proposed in this paper, the specific implementation measures are as follows:
- Upgrade the tension control system of the composite machine, adopt three-stage closed-loop control, set the unwinding tension to 2.0N/m, the conveying tension to 2.5N/m, and the winding tension gradient from 2.8N/m to 2.0N/m;
- Transform the pressure roller heating system, adopt electromagnetic induction heating, control the temperature uniformity error at ±1.5℃, set the pressure roller pressure to 0.4MPa, and the pressure difference compensation precision to ±0.03MPa;
- Conduct chromate passivation treatment on 0.006mm aluminum foil, and perform preheating dewatering (temperature 45℃) and corona treatment on the PET substrate;
- Select a low-viscosity polyurethane adhesive with a coating amount of 4g/m².
After implementation, the wrinkling defect rate of the enterprise’s products decreased to 2.1%, the tensile deformation rate was controlled within 1.2%, and the appearance qualification rate increased to 97.5%. The monthly waste loss was reduced by approximately 300,000 yuan, and the production efficiency increased by 15%, achieving significant economic benefits.
5. Development Trends of the Process
With the continuous improvement of product quality requirements in the flexible composite industry, the development of 0.006mm aluminum foil composite technology will show the following trends:
5.1 Intelligent Control
Introduce an AI visual inspection system to real-time identify the tensile deformation and wrinkling defects of the aluminum foil, and automatically adjust process parameters such as tension, temperature, and pressure to realize closed-loop intelligent production of “inspection-regulation-feedback” and further improve process stability.
5.2 Application of New Materials
Develop 0.006mm aluminum foil with high tensile strength (e.g., adding trace alloying elements such as Mg and Mn to increase the tensile strength to more than 180MPa) to reduce the risk of tension from the source of materials; sabay sabay, develop solvent-free adhesives to reduce volatile substances during the adhesive curing process, avoid interfacial bubbles, and improve composite quality.
5.3 Equipment Integration
Develop “pretreatment-composite-inspection-winding” integrated equipment to reduce the turnover links of aluminum foil during conveying, minimize the impact of external factors on the aluminum foil, and further improve composite precision.
6. Pangwakas na Salita
The tensile deformation and wrinkling problems of 0.006mm aluminum foil in the flexible composite process are rooted in the mismatch between its ultra-thin material properties, process parameters, and equipment precision. The current mature industrial process solutions can effectively solve such problems through technical approaches such as three-stage closed-loop tension control, temperature-pressure collaborative optimization, equipment precision improvement, and material pretreatment, significantly improving the quality and qualification rate of composite products. Both laboratory tests and enterprise application cases show that the optimized process can reduce the wrinkling defect rate to less than 3% and control the tensile deformation rate within 1.5%, meeting the production requirements of the industry. In the future, with the development of intelligent technology and new materials, the 0.006mm aluminum foil composite process will move towards a more efficient, stable, and environmentally friendly direction, providing support for the high-quality development of the flexible packaging industry.