In-Mold Labeling and the Role of Static Generation

by Stewart Gordon-Smith, business development manager, Meech International

In the eye of the consumer, the packaging of a product plays a fundamental role in the preservation of a brand’s image. One could argue that the label of a product acts as the corporate face of a brand, which means that poorly applied labeling (whether it is creased, inadequately aligned or displaying poor quality) will affect the consumer’s perception of the product and, therefore, the brand in question.

For companies looking to increase their consumer appeal and protect their products against contamination and counterfeiting, in-mold labeling (IML) provides the ideal labeling technology. A product decoration method that has experienced a surge in popularity throughout the past couple of decades, numerous industries are taking an active interest in this technology, including food, beverage, cosmetic, health care, pharmaceutical and even automotive.

The sector’s growth can be attributed to several factors, such as increasing technological advancements in the packaging sector that have led to cost-efficient manufacturing processes, as well as a surge in awareness among consumers about sustainable labeling and packaging.

The basics of IML

The term “in-mold labeling” derives from the manufacturing process in which a label is applied to a plastic packaging container. The label is placed within the mold as the container is being formed, instead of being applied to the surface of the finished product with an adhesive.

IML stands out thanks to its ability to provide better durability, reduce waste and costs, and deliver a noticeable improvement in the packaging’s quality. With the ability to insert printed labeling directly into a mold, whereby the label becomes a part of the packaging, the label is more durable than labels applied post-mold.

Advantages over traditional labeling include better moisture and product resistance, as well as superior tear and abrasion resistance, both of which extend the packaging’s shelf life. More importantly, the plastic films have shrinkages that are a better match for the container materials, therefore helping to significantly reduce the quality issues that arise with traditional labels.

Recycling has long been one of the primary incentives to invest in synthetic papers for IML applications, as plastic films (such as polypropylene, or polyethylene) share many of the chemical characteristics of the containers they decorate, which in turn allows them to be recycled along with the container.

Forming methods for IML

IML can be achieved via a number of forming methods, the two most popular being injection molding and blow molding. Both methods are effective for labeling applications, but each has a different set of characteristics.

Injection molding involves inserting molten plastic material into a cavity, or mold, which then takes the form of a container, while the label is fitted inside the cavity prior to the plastic being injected. Once the plastic material has been injected into the mold, it is allowed to cool, with the label effectively becoming amalgamated with the container. Among the key benefits that this method offers is the possibility to label all of a polygon-shaped container’s sides at the same time, a procedure which is not possible with glue-applied, heat transfer or pressure-sensitive labeling.

The blow molding process is not dissimilar to blowing up a party balloon. With the heated plastic material being extruded in the form of a tube, a mold is clamped around the pipe as a jet of air is blown out against the cavity walls to take the shape of the container. As with injection molding, the label is applied against the cavity wall and adheres to the formed container, due to the heat-activated glue on the label’s surface, as it cools down and settles into its final shape. Thanks to this method of molding, the container can be flexed and squeezed with no danger of the label peeling off the surface, therefore resulting in longer durability and also allowing the brand to reproduce higher quality graphics.

The role of static in IML

The biggest challenge in IML has always been ensuring that the label is successfully pinned to the mold according to specifications. While most businesses endeavor to limit the presence of static in their production environments to avoid quality issues and improve health and safety, in-mold labeling companies actually rely on static generation for the delivery of their products.

In the early days of IML, the label would be placed within the mold tool and held into the required position by using a vacuum system. This proved to be a flawed method due to mechanical issues, such as instances where a label was placed incorrectly into the tool and where molten plastic would block the vacuum channels. Furthermore, this process required a high level of maintenance and was more expensive than modern day systems. The most viable way of inducing an electrical charge on a label’s surface is pinning heads. While earlier pinning technologies would use large heads, the high levels of electrical charge stored in the heads could result in sparking, which would in turn damage the face of the mold tool. As a result, a smaller, resistive electric pinning system was necessary.

The solution to the difficulties encountered when dealing with diminutive containers and labels was the creation of a miniaturized IML pinning system specifically designed for use in applications where small items are being molded.

Meech 994 Hydra HR. Photo courtesy of Meech.

The Meech 994 Hydra is a system of this kind, providing repeatable pinning with no degradation over time. The components are easy to mount, as well as being straightforward to connect and disconnect during mold tool changes. The design of these systems eliminates the chance of sparking and the possibility of expensive damage to the mold tool. The choice of materials ensures that the problem of potential contamination of the container, sometimes seen with conductive foam-based IML systems, is eliminated.

The future of the IML industry

IML Static Generator. Photo courtesy of Meech.

The global IML market looks set to thrive over the coming years, with a reduction in labeling costs being a major contributor to this projected growth. Aside from being 100 percent recyclable and eliminating the need for labeling processes on manufacturing lines, IML’s key strength is its ability to help maximize packaging appeal, prevent label tampering and guarantee superior adhesion.

These traits mean that, as long as there are demands for high-quality packaging, clear instruction labeling or a damage-resistant finish, there will be a role for in-mold labeling. And, with static control being a key component of the IML process, there also will be a requirement for label pinning technologies that ensure that end product quality always is guaranteed.

Stewart Gordon-Smith has held a number of positions since joining Meech in 1996, giving him a wealth of experience in industrial static control solutions. Over the years, he has worked closely with the engineering department to improve quality specifications of Meech’s technology ranges, and he also has helped develop market share in the sale of static control, web cleaning and air technology systems. In his current role as business development manager, he is responsible for developing sales of Meech products in new territories, including South America and the Middle East. For more information, call +44 (0) 1993 706700 or visit