Enhanced Solutions for Preventing Label Wrinkling and Lifting in Humid Conditions

Introduction

In June 2016, we shared an article titled "Tips for Carton Labeling During Plum Rain Season" that received positive feedback from readers. As this year's rainy season approaches, Avery Dennison's Technical Service Department has prepared this upgraded version of tips, hoping to assist both converters and end-users.

Currently, most carton labeling in the market involves blank die-cut paper face materials printed and applied to corrugated cartons. In conditions of high air humidity, especially during rainy weather, many users have encountered problems such as wrinkling​ or lifting​ after labels have been applied to cartons for some time. Specific defect manifestations are shown in the accompanying images.

01 Cause Analysis

● Asynchronous Deformation of Labels and Cartons in Humid Environments

Since paper fibers expand when absorbing moisture, and kraft cartons and paper label materials have different water absorption rates, their expansion or contraction degrees vary under high humidity conditions. When deformation is not synchronized, severe cases result in lifting or wrinkling.

Corrugated cartons are typically made from three-layer or five-layer corrugated board with different specifications like A-flute and B-flute. The production process requires adhesive application and heating. Due to variations in raw materials and manufacturing processes, cartons undergo dimensional changes under different temperature and humidity storage and usage conditions. Particularly during the plum rain season when environmental humidity is high and fluctuates dramatically, carton dimensional stability is significantly affected, making labels prone to wrinkling and lifting.

● Inadequate Label Smoothing

Inadequate smoothing means labels don't fully bond with the substrate, leaving air gaps. When air humidity is high and cartons are damp, more thorough smoothing is necessary to achieve initial tack, which can somewhat suppress lifting or wrinkling.

02 Improvement Recommendations

● Ensure Newly Manufactured Cartons Are Stabilized

Newly produced cartons should be allowed to equilibrate in standard environmental conditions for sufficient time until stabilized before labeling.

● Prevent Moisture Exposure During Label and Carton Transportation and Storage

Use proper packaging and improve transportation and storage environments to avoid moisture exposure for both labels and cartons.

● Balance Label and Carton Conditions

If labeling conditions cannot be improved (e.g., in damp environments), place both labels and cartons in the same environmental conditions where labeling will occur. Allow them to equilibrate for a period before labeling, then verify labeling results.

● Select Appropriate Label Adhesives

First, high-tack adhesives help resist lifting and wrinkling. Higher tack reduces lifting risk. Second, under high humidity conditions when labeling kraft cartons, water-based and hot-melt adhesives each have their advantages. Compared to hot-melt adhesives, water-based adhesives' affinity for moisture can somewhat alleviate wrinkling caused by paper fiber moisture absorption. Hot-melt adhesives' water-resistant properties give them an edge in initial tack performance on damp surfaces.

It's particularly important to note that both water-based and hot-melt adhesive labels have limits regarding water and moisture resistance. Excessive moisture can cause adhesive failure and even damage face materials and label structure. Users should follow product manual instructions.

● Ensure Proper Label Smoothing

Compared to normal air humidity conditions, thorough smoothing becomes particularly crucial during the high-humidity plum rain season.

● Align Paper Fiber Direction Between Labels and Carton Surface

If labeled cartons will inevitably experience significant environmental changes, aligning the fiber direction of labels with that of the carton labeling area will improve resistance to environmental impacts and reduce wrinkling and lifting risks.

Conclusion

The above recommendations are based on the performance characteristics of labels and cartons, combined with long-term accumulated labeling application experience. We hope these suggestions help with preventive measures. Additionally, if you encounter actual cases during rainy season, you can begin with manual labeling tests and analysis based on these guidelines.

For challenging cases, please contact relevant Avery Dennison sales and technical personnel.