2022/08/30
1. Seal Strength
When explaining packaging materials to customers, we sometimes use the term “seal.”
“Seal” refers to the process of applying heat to film to melt it and bond two films together. This is also called “heat sealing.”
The term “seal strength” refers to the difficulty of peeling off this “seal.”
When explaining seal strength, the properties of each resin are important.
For example, resins with strong seal strength include “polyethylene” such as “low-density polyethylene” and “metallocene polyethylene.”
The reason why polyethylene has strong seal strength is that its melting point is around 150-170 degrees Celsius, which is very low among film products. It melts easily even at low temperatures and cools stably, resulting in stable seal strength.
Conversely, some films have very weak sealability or cannot be heat-sealed at all.
For example, PET (polyethylene terephthalate) and OPP (oriented polypropylene) fall into this category.
PET film and OPP film undergo a process called “orientation” (literally stretching the film vertically and horizontally) during film formation.
Orientation changes the molecular structure and increases the melting point, which reduces the heat seal strength.
So why do we orient the film? Orientation provides the following characteristics:
Increased strength
Increased transparency
Increased gloss
Increased gas barrier properties
Increased moisture resistance
It is difficult to use oriented film alone as a bag.
Therefore, to utilize its characteristics, it is laminated with polyethylene, which has high seal strength.
The inner layer of the bag is made of polyethylene, and heat sealing is performed. By the way, laminating films is called “lamination.”
By laminating films with different characteristics in this way, high-performance laminated films are used in a wide range of applications.
Especially for food packaging, OPP, PET, or nylon is often used for the outer layer of the bag, and polyethylene (PE) is used for the inner layer.
The oriented film in the outer layer protects against dryness and oxidation, while the polyethylene film in the inner layer provides seal strength.
2. Life in the Philippines Diary
In this issue, I will talk about the water outage.
One day, the water suddenly stopped working in our company. Since there were times when water was unavailable for a day due to maintenance, I thought this was also maintenance. However, even after one day, two days, and a week, the water did not come back.
Not only our company but also neighboring companies were affected. When I checked with our employees, they told me that the water supply pipe was broken and unusable.
Also, it was said that it would take time to procure parts, and the repair schedule was undecided. In the end, we were without water for about two weeks. I experienced something truly “Philippine-like” after a long time.
During this time, buckets were prepared for the toilets, and we had to flush the toilets ourselves with the water. I couldn’t hide my shock, thinking, “I’ve never experienced this in Japan.”
On the other hand, Filipinos are used to such troubles, so they calmly drew water from the water tank into buckets and set them up in the toilets.
I thought I was getting used to life in the Philippines, but I realized that there are still many things I haven’t experienced.
