When the hose is stored for a long time or squeezed repeatedly, will the aluminum foil barrier layer develop pinholes or cracks due to deformation?

HW-A. Definition of the Core Issue: Nature and Risks of the Aluminum Foil Barrier Deformation Issue

In tube packaging, the aluminum foil barrier (typically 0.006~0.015mm thick soft aluminum foil, mostly using grades such as 1235 и 8011) serves the core function of blocking the penetration of oxygen (O₂), водена пареа (H₂O), and volatile substances. It is widely used in pharmaceuticals (на пр., ointments, gels), daily chemicals (на пр., toothpaste, hand creams), and food products (на пр., jams, sauces). Ова aluminum foil barrier deformation issue is the primary cause of its functional failure, directly related to the shelf life and safety of the contents.
Key Conclusion: Under conditions of long-term storage (≥3 months) or repeated squeezing (≥100 cycles), this deformation issue gradually emerges with stress accumulation—aluminum foil will inevitably develop microcracks due to deformation, which may evolve into pinholes in severe cases. The degree of damage is directly associated with stress type (static/dynamic), environmental factors, и материјални својства, requiring targeted prevention and control of such deformation-related challenges.

HW-B. In-depth Analysis of Damage Mechanisms: How Long-term Storage and Repeated Squeezing Induce This Deformation Issue

(А) Long-term Storage: This Deformation Issue Caused by Static Deformation and Environmental Synergy

① Internal Stress Accumulation Due to Thermal Expansion and Contraction

The thermal expansion coefficient of aluminum foil (23.1×10⁻⁶/℃) differs significantly from that of tube substrates (на пр., 180×10⁻⁶/℃ for PE, 150×10⁻⁶/℃ for PP). Long-term temperature fluctuations (на пр., diurnal temperature difference >15℃ in warehouses) lead to asynchronous deformation between the two, becoming the primary trigger for this deformation issue:

• At low temperatures (<10℃): The substrate shrinks more than the aluminum foil, stretching the aluminum foil to generate tensile stress and form “microfolds”;

• At high temperatures (>30℃): The substrate expands more than the aluminum foil, compressing the aluminum foil to generate compressive stress, со “stress concentration points” appearing at the folds.

Over time, after continuous cycles, microcracks (0.005~0.01mm) initiate at the stress concentration points. If the environmental humidity exceeds 65%, water vapor penetrates the cracks, accelerating the electrochemical corrosion of алуминиумска фолија (specifically, the standard electrode potential of aluminum is -1.66V, making it prone to anodic dissolution). This causes the cracks to expand into pinholes (diameter >0.02мм), further exacerbating this deformation issue.

② Plastic Deformation Under Static Pressure

Дополнително, during stacked storage of tubes (common stacking height: 1.2~2.0m), the static pressure on the bottom tubes can reach 0.3~0.5MPa. The aluminum foil barrier undergoes “creep” under this pressure (the room-temperature creep rate of soft aluminum foil is approximately 1×10⁻⁸/s), which worsens this deformation issue:

• Local areas (на пр., tube bottom, tube mouth shoulder) experience deformation exceeding the yield strength of aluminum foil (the yield strength of 1235 aluminum foil is approximately 45MPa), формирање “plastic dents”;

• The aluminum foil at the dents thins (на пр., from 0.01mm to 0.006mm), reducing crack resistance. After long-term storage (>6 месеци), “penetrating pinholes” are likely to form. Particularly when the contents contain acidic substances (pH <5, such as citric acid, salicylic acid), corrosion accelerates pinhole formation, upgrading this deformation issue from “simple deformation” до “complete functional failure”.

(B) Repeated Squeezing: This Deformation Issue Caused by Dynamic Fatigue

① Stress Concentration and Fatigue Damage

By contrast, when a tube is squeezed, the deformation of the aluminum foil barrier concentrates in the “squeezing contact area” (accounting for 15%~20% of the tube’s surface area). This area endures dynamic stress of 80~120MPa (far exceeding the yield strength of aluminum foil), and the stress direction changes repeatedly (tension-compression cycles) with each squeezing action—this is the main manifestation of the deformation issue during use:

• Initially, first squeeze: The aluminum foil undergoes “elastic deformation”; if the force exceeds the elastic limit (approximately 30MPa), 0.5%~1% plastic deformation remains;

• Subsequently, repeated squeezing (≥50 cycles): Plastic deformation accumulates, initiating “fatigue microcracks” (length: 5~10μm) at stress concentration points (на пр., tube folds, weak bonding areas between aluminum foil and substrate);

• Eventually, squeezing cycles >300: Microcracks propagate along the grain boundaries of aluminum foil (the grain size of aluminum foil is typically 10~20μm), формирање “penetrating cracks” (ширина: 0.01~0.03mm). If cracks intersect, “pinhole-like defects” (aperture: 0.03~0.05mm) form, and this deformation issue ultimately leads to the failure of the barrier function.

② Coating Peeling and Aluminum Foil Exposure

Покрај тоа, aluminum foil barriers are usually compounded with polymer coatings (на пр., acrylic resin, PVDC) to enhance adhesion and corrosion resistance. During repeated squeezing, “shear stress” is generated at the interface between the coating and aluminum foil, which indirectly exacerbates this deformation issue:

• If the coating adhesion is insufficient (<3N/25mm, per ASTM D3359 standard), “coating peeling” occurs;

• The exposed aluminum foil directly contacts the contents or air: on one hand, it suffers “mechanical scratches” from friction with the contents (на пр., toothpaste containing particles); Од друга страна, it undergoes “oxidative corrosion” (forming Al₂O₃, whose volume expansion causes crack propagation). Under the combined effect, the pinhole formation rate increases by 3~5 times, making this deformation issue more difficult to control.

HW-C. Quantitative Analysis of Key Factors Affecting Damage Degree: Basis for Targeted Resolution of This Deformation Issue

Notably, these factors do not act independently; their interactions often amplify the severity of this deformation issue. На пример, high storage temperature (35℃) combined with frequent squeezing (20 times/day) can reduce the aluminum foil’s fatigue life by more than 50%, compared to optimal conditions (25℃, 5 times/day).

HW-D. Professional Testing and Evaluation Methods: Accurate Identification of This Deformation Issue

(А) Non-Destructive Testing Technologies: Accurate Identification of Micro-Damage and Localization of the Deformation Issue

① Laser Confocal Scanning Microscopy (LCSM)

• Principle: Scans the aluminum foil surface with a 532nm laser, achieving a resolution of 0.001mm and capturing microcracks smaller than 5μm;

• Апликација: Detects the surface morphology of aluminum foil after long-term storage, quantifying crack length, ширина, and density (на пр., “10 cracks/mm², average width 0.008mm”) to directly visualize the microstate of this deformation issue.

② Vacuum Decay Method (ASTM F2338)

• Principle: Places the tube in a vacuum chamber; if pinholes exist, the chamber pressure rises over time, and the equivalent aperture of pinholes is calculated based on pressure changes;

• Precision: Detects pinholes ≥0.005mm, suitable for tightness verification (на пр., pharmaceutical tubes must meet “pressure change <0.1kPa/5min”), indirectly reflecting the severity of this deformation issue.

③ Ultrasonic Testing (UT)

• Principle: High-frequency ultrasound (20~50MHz) penetrates the tube; abnormal reflection signals occur at damaged areas of the aluminum foil;

• Advantage: Detects delamination between aluminum foil and substrate (an indirect indicator of deformation damage) with a detection depth of 0.1~5mm, assisting in determining the impact range of this deformation issue.

(B) Mechanical and Aging Tests: Evaluating Damage Resistance and Predicting the Deformation Issue

① Fatigue Life Test (Simulating Repeated Squeezing)

• Опрема: Dynamic mechanical testing machine (на пр., Instron 5969), set with a squeezing stroke of 5~10mm and frequency of 1Hz;

• Indicators: Records the “crack initiation cycle count” (number of cycles when 0.01mm cracks first appear) и “fracture cycle count” (number of cycles when cracks penetrate), predicting when this deformation issue will emerge during use.

② Thermal Cycling Aging Test

• Conditions: -40℃ (2h) →70℃ (2h), 100 cycles;

• Евалуација: After cycling, tests the barrier property of aluminum foil (oxygen transmission rate, per ASTM D3985). If the transmission rate increases from 0.1cm³/(m²·24h) до >1cm³/(m²·24h), it is determined as “severe damage”, indicating that this deformation issue has caused functional failure.

HW-E. Industry Practices and Optimization Solutions for Damage Prevention: Systematic Resolution of This Deformation Issue

(А) Material and Structural Optimization: Reducing This Deformation Issue at the Source

① Aluminum Foil Material Upgrade

• Adopts “high-purity + high-ductility” алуминиумска фолија (на пр., 99.9% Ал, elongation at break 25%) to reduce stress concentration points caused by impurities, fundamentally lowering the occurrence probability of this deformation issue;

• Compounds with “nano-ceramic coatings” (на пр., Al₂O₃-SiO₂ composite coating, thickness 50~100nm) to enhance corrosion resistance and wear resistance, reducing the pinhole formation rate by 60% and alleviating subsequent damage caused by this deformation issue.

② Tube Structure Improvement

• Покрај тоа, adopts “gradient wall thickness design”: Increases the wall thickness of easily deformable areas (на пр., tube mouth, bottom) from 0.5mm to 0.8mm to buffer squeezing stress and reduce local deformation, targeting the concentrated occurrence points of this deformation issue;

• Introduces an “elastic recovery layer”: Adds TPE (thermoplastic elastomer) between the aluminum foil and PE layer to increase the elastic recovery rate after squeezing from 60% до 90%, reducing plastic deformation accumulation and inhibiting the development of this deformation issue at the structural level.

(B) Storage and Usage Specifications: Process Control of the Deformation Issue

① Storage Condition Control

• Adopts “layered stacking” (layer height ≤30cm) to ensure the static pressure on the bottom tubes is ≤0.2MPa, avoiding excessive static pressure triggering this deformation issue;

• Equips warehouses with temperature and humidity control systems to avoid diurnal temperature difference >10℃ and RH fluctuation ≤15%, reducing the superimposed impact of environmental factors on this deformation issue.

② User Guidance

• Дополнително, labels tubes with “recommended squeezing area” (middle part, uniform stress distribution) и “no excessive squeezing” warnings to guide correct user operation, reducing the occurrence rate of this deformation issue during use;

• Designs “one-time sealing structures” for pharmaceutical tubes to avoid additional deformation caused by repeated opening (на пр., aluminum foil sealing film opening ≤3 times), reducing this deformation issue caused by human factors.

(В) Typical Industry Cases: Practical Solutions for This Deformation Issue

① Pharmaceutical Ointment Tubes (Case of a Multinational Pharmaceutical Enterprise)

• Issue: Stored long-term in the hot and humid environment of Southeast Asia (32℃, RH85%), this deformation issue intensified with temperature and humidity. After 6 месеци, 30% of the tubes’ aluminum foil developed 0.02~0.05mm pinholes, with excessive oxygen transmission rates;

• Решение: Switched to “99.9% алуминиумска фолија + PVDC composite coating” to enhance deformation and corrosion resistance, and optimized storage conditions (25℃, RH50%) to reduce environmental triggers. After 6 месеци, this deformation issue was effectively controlled, with the pinhole formation rate dropping to 2% and qualified transmission rates.

② Daily Chemical Toothpaste Tubes (Case of a Domestic Enterprise)

• Issue: Repeated squeezing by users (15 times/day) caused dynamic stress to accelerate the emergence of this deformation issue. After 3 месеци, 0.01~0.03mm cracks appeared on the tube shoulders;

• Решение: Increased the fillet radius from 0.8mm to 1.2mm to disperse stress, and raised the aluminum foil’s elongation at break from 18% до 25% to enhance deformation resistance. This increased the fatigue life against this deformation issue from 400 до 1200 cycles, meeting the 1-year service requirement.

HW-F. Conclusions and Future Development Directions: Continuous Optimization of Strategies for This Deformation Issue

(А) Core Conclusions

Under long-term storage (static deformation + environmental corrosion) and repeated squeezing (dynamic fatigue + coating peeling), this aluminum foil barrier deformation issue in tube packaging gradually develops, leading to pinholes and cracks. The degree of damage can be quantitatively regulated through material properties, structural design, and environmental control. Следствено, the industry needs to establish a full-chain prevention and control system “from material selection to usage guidance” to systematically resolve this deformation issue and ensure packaging functionality and content safety.

(B) Technological Development Trends

• Material Sector: Develop “self-healing aluminum foil” (added with microcapsule repair agents that release resin to seal cracks when they form) to address this deformation issue through active repair;

• Testing Sector: Apply “AI visual inspection systems” (real-time monitoring of micro-damage on aluminum foil during production with a recognition rate ≥99.5%) to detect early signs of this deformation issue;

• Design Sector: Adopt “finite element simulation” (simulating squeezing deformation in advance to optimize stress distribution and reduce damage risks) to avoid triggers of this deformation issue at the design source.