Design of plastic packaging containers such as "high set", heat shrinkable labels need to be selected

[China Packaging News] Common packaging containers mainly include plastic containers, paper containers, glass containers, metal containers, and wooden containers. Among them, the most widely used heat shrinkable labels are plastic containers, such as: PET , PP , HDPE , PS base material containers. Designing packaging for containers, just like tailoring, designers also need to have a certain understanding of the characteristics of containers and label materials in order to be able to choose the most suitable " cloth " , combined with the " body " characteristics of the container , fully show the designer's intention . Here are some basic principles that should be paid attention to in the selection of labels.

1. Consider the container shape

In order to make the shape of the product more visually impactful, designers often design a lot of special-shaped structures on the container. In this way, the adaptability and expressiveness of traditional silk-screen printing, labeling, and self-adhesive labels are greatly limited. Only heat-shrinkable labels can perfectly follow the shape of the container and display stronger expressiveness.

This requires that when selecting the label material, it must be considered whether the shrinkage rate of the material used can meet the maximum required shrinkage rate of the container, otherwise skirts, wrinkles and other undesirable phenomena are likely to occur. We combine the following legend to illustrate.

Analysis chart of shrinkage requirements for special-shaped containers

If the design height of the label is a , the maximum thermal shrinkage of the material must satisfy Fmax > α

If the design height of the label is b , the maximum thermal shrinkage of the material must satisfy Fmax > β

It should also be emphasized here that when determining whether the maximum shrinkage of the material is suitable for container packaging, a certain difference must be ensured, because the temperature that the label is actually exposed to during the production process is usually 85 ~ 95 ° C , so it is difficult to achieve The environment in which the material shrinks under boiling water. Therefore , the shrinkage rate of the material at 80 ℃ and 90 ℃ has a key effect on the shrinkage effect of the label.

2. Consider the container material

When the label and the container enter the heat-shrinkable channel for shrink setting, the container will produce a certain degree of thermal expansion, and the label undergoes a heat shrinkage change. The two changes are simultaneous and relative. When leaving the high temperature to start cooling, the label quickly cools and sets, and the container shrinks relatively slowly due to the physical properties of the material and the wall thickness. Between the expansion and contraction of the container, the label and the container are likely to form a suspended state. This not only makes the label look loose and collapses, which affects the appearance. It is also prone to the risk of re-labeling and falling on regular cylindrical containers and cup-shaped containers, which brings great security risks to product packaging.

How to overcome these problems? Let's take a look at the shrinkage rate of the plastic container material itself.

Comparison Table of Shrinkage of Common Plastic Containers

It can be seen from the table that the shrinkage rate of common containers is PET (that is, polyester) < PS < PP < HDPE , so especially for PE containers, try to choose materials with good followability or low temperature shrinkage, such as OPS , low temperature shrinkable PET , PVC, etc.

3. Consider the matching of container and label materials

Try not to choose the same material for containers and labels. Because, when the material is heated to its softening point, the container and label are prone to melt adhesion, which has a certain adverse effect on the appearance of the package and the classification and recycling. If you must choose the same material, you need to print the ink or varnish to isolate the label from the container.

4. Consider the strength of the shrinkage stress of the label material

The stiffness of the container must be stronger than the shrinkage stress when the label shrinks, otherwise under the effect of the shrinkage stress, the container is easily squeezed by the label stress, affecting the container volume, and even causing the container to deform. In the packaging process of first labeling and then canning, some plastic containers have a weak wall and a low stiffness. When the shrinkage stress of the label is large, the volume of the container will be reduced (of course, the reason for the change in the volume of the container is also the effect of the shrinkage of the material). The lighter carton, plastic sheet blister or stamping simple packaging box, which is more common, tends to collapse when the material stiffness is relatively soft and shrinks. The shrinkage stress of common materials in order is: PET > PVC > OPS .

To complete the packaging of shrink labels to finally realize the designer's concept, not only need to consider the characteristics of the container, but also need to consider the matching of the label and the shrink channel, just like " cloth " is selected, " cut " is fixed, we need to choose Suitable " sewing equipment " .