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In recent years, the packaging industry has faced several challenges with materials like PET and PVC. PET suffers from oxygen permeability, poor adhesion of PE ink, color migration, and high tensile elongation, which makes it prone to wrinkling. It’s also difficult to overprint, while PVC is toxic and requires high-frequency heat sealing, leading to potential film breakage. PT films have weak tear resistance and tend to shrink at high temperatures, reducing their strength or making them brittle. These issues have made aluminum (AL) and aluminized films more popular as substrates in flexible packaging.
However, AL and aluminized films can cause quality problems if not handled carefully during processing and lamination. Common defects such as “spots†and “white spots†are frequently seen in composite products, especially when using aluminized films. These issues are more prevalent than those found in plastic/plastic or aluminum/plastic laminations, causing headaches for many manufacturers.
To address these problems, I was invited to investigate quality issues in aluminized film composites in printing and packaging plants across Hangzhou, Wenzhou, Zhejiang, Wuxi, Jiangyin, Zhengzhou, and Xinxiang. The following points summarize the causes and solutions for common defects like “spots†and “white spots.â€
First, the appearance of “speckled†areas on aluminized films is often due to three main factors:
1. Poor quality of the aluminized film itself, such as uneven coating or rolling, can lead to white or gray spots after lamination. This happens when the ink or adhesive doesn’t adhere well, resulting in weak interlayer bonding and visible spots.
2. Inks with low hiding power and poor tightness may be affected by solvents in the adhesive, leading to color variation and spot formation. This is especially true when the ink layer is infiltrated by ethyl acetate.
3. Low-quality adhesives that don’t bond well with the aluminized layer can cause uneven coating, leading to spotting. High initial tack and poor solvent release further contribute to this issue, especially at high speeds.
To reduce these problems, using inks with better hiding power and suitable adhesives for aluminized films is essential. Additionally, adjusting the anilox roller depth, reducing operating concentration, and slowing down the process can help minimize spots.
Another common issue is the formation of “white spots,†which may appear randomly on the surface. These spots can vary in size and are more noticeable in light-colored prints. Causes include large ink particles, high adhesive surface tension, and improper equipment settings. Solutions involve controlling ink particle size, using specialized adhesives, and ensuring proper drying and coating processes.
For pinholes or pits caused by ink defects, adjustments to the composite roller, increased plastic coating, and the use of defoamers can help. Improving blade angle, adding erasers to scrapers, and enhancing ink viscosity are also effective strategies.
Overall, addressing these issues requires a combination of material selection, process optimization, and quality control. By focusing on high-performance additives and new materials, the packaging and printing industry can improve the quality of aluminized film composites and meet growing market demands.