Flexible Food Packaging Defects Push Manufacturers to Strengthen Lamination Process Control

Wrinkling, bubbling, and delamination are among the most common quality complaints in the flexible food packaging industry. Many manufacturers assume these problems are caused by poor film materials, but in reality, more than 90% of packaging bubbling and delamination issues are related to lamination processes, curing control, production environments, and post-production handling.

For food brands working with a Flexible Packaging Supplier, understanding these process-related defects is important because wrinkling, bubbling, and delamination often appear after curing, storage, or machine use rather than immediately after production.

Even with the same packaging structure and materials, slight process deviations can cause large-scale defects, air leakage, delamination during shelf life, and visible appearance problems, resulting in customer complaints, returns, and production losses.

1. Packaging Bubbling: Usually Caused by Residual Air and Uneven Curing

Packaging bubbling generally falls into two categories:

• immediate bubbling during lamination
• bubbling after curing

The causes are completely different.

Immediate bubbling usually occurs during rewinding after lamination. The main reason is uneven adhesive coating or microscopic air gaps during the bonding process.

Common causes include:

• uneven adhesive coating thickness
• worn doctor blades
• local adhesive interruption
• dust, fibers, or oil contamination on film surfaces

These problems trap air between film layers and create dense microbubbles.

Post-curing bubbling is usually caused by incomplete adhesive curing. Incorrect adhesive ratios or curing agent imbalance can cause residual gas generation during curing. In high-barrier aluminum foil or metallized packaging structures, gas cannot escape easily, making bubbling problems much more severe.

Practical Solutions

• Maintain dry lamination adhesive coating at 2.8–3.5g/m²
• Inspect doctor blades daily
• Control adhesive mixing ratios accurately
• Extend degassing and relaxation time for high-barrier packaging structures

2. Packaging Delamination: Caused by Poor Adhesion and Incorrect Tension Control

Delamination is one of the most serious packaging defects because it directly causes:

• air leakage
• liquid leakage
• barrier failure
• food spoilage

The two major causes are insufficient surface treatment and incorrect tension settings.

Insufficient Surface Treatment

PET, PE, and VMPET films require proper corona treatment. If surface tension drops below 38 dyn, adhesives cannot properly bond to the film surface.

This often causes:

• layer separation
• aluminum transfer
• adhesive failure after curing or low-temperature storage

Metallized films are especially sensitive to insufficient corona treatment.

Incorrect Lamination Tension

Different materials have different stretch properties:

• PET has high rigidity
• PE has high flexibility
• aluminum foil has almost no elongation

If the same tension settings are used for all materials, residual internal stress may build up during lamination.

After bag forming, folding, or low-temperature storage, stress release may cause large-scale delamination.

Practical Solutions

• Check film surface tension before production
• Do not use films below 38 dyn
• Reduce rewinding tension by approximately 20% for aluminum foil structures
• Maintain curing temperatures at 50–55°C for 12–24 hours

3. Packaging Wrinkling: Mostly Caused by Residual Stress and Improper Rewinding

Packaging wrinkles are generally divided into:

• regular longitudinal wrinkles
• irregular random wrinkles

Most wrinkling problems are caused by poor downstream production control rather than film material defects.

Regular Longitudinal Wrinkles

These are usually caused by excessive rewinding tension.

When rewinding tension is too high, films are overstretched and generate internal stress. After curing, film shrinkage creates visible longitudinal wrinkle lines.

Irregular Wrinkles

Irregular wrinkles are commonly caused by:

• web misalignment
• uneven roller pressure
• inconsistent rewinding tightness

High humidity also increases wrinkling risks. When workshop humidity exceeds 65%, PE films absorb moisture and become softer, reducing web stability.

Practical Solutions

• Regularly calibrate roller pressure
• Replace worn guide rollers
• Use low-tension soft rewinding for soft PE structures
• Maintain workshop humidity at 45%–55%
• Allow laminated rolls to rest for 4 hours after curing before slitting

4. Common Packaging Defects and Process Standards

Defect	Main Cause	Recommended Standard	Practical Solution
Dense microbubbles	Uneven adhesive coating, surface contamination	Adhesive coating ≥2.8g/m²	Clean blades and calibrate coating system
Large bubbles after curing	Incorrect adhesive ratio, trapped gas	Adhesive ratio error ≤±2%	Adjust curing agent ratio and extend degassing time
Delamination and aluminum transfer	Low corona treatment, incorrect tension	Surface tension ≥38 dyn	Re-corona treatment and adjust lamination tension
Regular longitudinal wrinkles	Excessive rewinding tension	Rewinding tension ≤0.3MPa	Reduce rewinding tension
Irregular wrinkles	Roller imbalance, high humidity	Workshop humidity 45%–55%	Calibrate rollers and control humidity

5. Why Most Packaging Defects Are Actually Process-Control Problems

Most wrinkling, bubbling, and delamination problems are not caused by poor raw materials. In most cases, they are caused by insufficient control over:

• adhesive coating
• lamination tension
• curing conditions
• workshop environment

Many packaging factories focus only on finished product appearance while ignoring defects that appear after curing, storage, or transportation.

Strict process control, standardized production management, and stable environmental conditions remain the most effective ways to prevent packaging bubbling, wrinkling, and delamination problems in food packaging production.