The workshop hygrometer often shows erratic readings during the humid spring and rainy seasons. For sealing film production, this means you can't just stick to one standard operating procedure. Temperature and humidity shift — and if you don't adjust accordingly, the quality of an entire batch can fluctuate.

When temperature and humidity change, film performance changes too

In hot, humid conditions, the air is full of moisture, and this significantly affects the adhesives used in sealing film. For example, polyurethane adhesives can hydrolyze in hot, humid environments, leading to reduced seal strength. High humidity also causes some film materials (like nylon film) to absorb moisture, changing their shape and properties, which affects sealing results.

In winter, low temperatures bring a different set of problems. Adhesives become thicker and less fluid at low temperatures, leading to uneven coating and potentially substandard composite strength. Films also become stiffer and less flexible in cold conditions, making them more brittle during sealing, with heat seal strength potentially fluctuating.

In addition, temperature and humidity directly affect the coefficient of friction. In summer, high humidity makes the film surface too slippery, causing rewound rolls to collapse. In winter, dry conditions make the film feel too rough, potentially causing machine jams. These subtle changes are often the root cause of production line issues.

How to adjust? By season, by step

When facing seasonal changes, the adjustment principle is: "Cool and dehumidify when it's hot; preheat and insulate when it's cold." The specific approach depends on workshop conditions.

During hot, humid conditions, the key is to control moisture in the workshop. If possible, air conditioning with dehumidification is the most effective solution. If not, and humidity is very high, you can temporarily adjust the adhesive formulation — for example, increasing the curing agent ratio by 3%–5% — while taking extra care to prevent materials from absorbing moisture prematurely.

During cold, dry conditions, the key is to "warm up" materials and equipment. You can preheat films and adhesives in a curing chamber before use, and heat the adhesive tank and composite hot rollers as well. Static electricity is more common in winter, so you'll also need to manage humidification and static elimination in the workshop to ensure safety.

There's no fixed set of parameters for sealing film production. The key is to make dynamic adjustments to temperature, pressure, and adhesive formulation based on seasonal and environmental changes. This requires experience — and a deep understanding of the materials themselves.

If you encounter sealing quality fluctuations due to seasonal changes, Leadtra Packaging can provide targeted technical recommendations based on your specific production line and environmental conditions.