The Ins & Outs of Choosing Materials for Chemical Container Labeling

In today’s market, there are a multitude of options for chemical container labeling, including vinyl, polyester and polypropylene films; and thermal transfer, laser and UV inkjet printing. The purpose of such labels, of course, is to ensure that companies and their employees, as well as the public, are made aware of chemical hazards so they can take the necessary steps to prevent exposure and understand the possible impact on their health should exposure occur. The Globally Harmonized System of Classification and Labeling of Chemicals (GHS) requires that certain information appear on all container labels and recommends certification of label materials and inks under BS 5609.

Needless to say, determining the most appropriate materials for your chemical container labeling application can be overwhelming. We reached out to some of the technical and marketing folks at ARMOR, as well as our own market development specialists, for some insight on selecting materials for chemical container labeling. Here’s what they had to say.

Durability is the name of the game – that of the film, the adhesive and the inks. Under BS 5609, certification testing falls into two categories: Section 2 - durability of the film and adhesive in connection with exposure to salt water, temperature variations, weathering and sunlight; and Section 3 - durability of inks against abrasion. BS 5609 certification is required under the International Maritime Dangerous Goods Code for chemicals that will traverse the ocean. It is not required otherwise, however, the vast majority of end users will specify BS 5609 to help limit liability.

Printing

To date, thermal transfer printing is the most widely tested print technology and remains the most reliable for chemical labeling applications. Resin ribbons are typically the ribbon-type of choice due to their superior durability. However, wax/resin ribbons may be perfectly suitable depending on the exposures the labels may encounter, such as when containers won’t be exposed to the outdoors or handled aggressively, and spillage is not a concern. Ultimately, the Section 3 approval will dictate what ribbons may be used.

Beyond durability of the inks, there are some additional considerations when choosing ribbons. GHS requires both black and red, but there are many grades of black ribbons and only limited choices for red. Furthermore, while there are thermal transfer printers with dual color capabilities, they usually have the same heat setting for both colors, so it’s important that the ribbons have similar melt points. Otherwise, one or the other won’t transfer properly, leading to poor print quality.

Print speed is also a factor for optimizing print quality. Slower speeds require a lower temperature so as to avoid burning the film, which will result in wrinkle marks, as well as turning inks a grayish brown, both of which lead to poor barcode quality. Conversely, when running faster, the temperature may need to be elevated to ensure an adequate transfer of ink.

Films and Adhesives

The appropriate choice of film and adhesive is dependent on several things.

Container material. The surface energy of metal, cardboard, plastic and glass are all different, so an adhesive that adheres well to one may not adhere as well to another. Furthermore, if the container will be reused, an adhesive that can later be removed when the end user wishes to refurbish or reuse the container may be desirable.

Filling. Label adhesion can be impacted by the point at which filling occurs. If it will occur before labeling, there is a likelihood that labels will be exposed to the container contents. Polyesters (PET) tend to perform the best when exposed to caustic chemicals, but if cost is a factor, polypropylene (PP) may be a suitable alternative. If the container is a plastic and the chemical going into it will be hot upon filling, however, the container may shrink on cooling, causing distortion or edge lift of a PET or PP label. In this case, vinyl may be preferred because it can expand and contract with the container.

Exposures. There are numerous adhesives in the labeling industry that are suitable for chemical container labeling. Choosing the right one is dependent on multiple factors, such as the various conditions to which the label could be exposed. These include the container contents, of course, but also weather, temperature extremes, UV rays, and salt water, if the container will be transported overseas. For example, if labels will be applied at cold temperatures or be exposed to them, a softer adhesive is required for labels to adhere properly and remain adhered. For high temperatures, on the other hand, a firmer adhesive that still has some give is needed to avoid piping and wrinkling.

GHS went into full effect in 2016, but non-compliant labels continue to exist, and the legal ramifications of a serious injury due to non-compliance could be significant. Furthermore, in the U.S., OSHA’s Hazard Communication Standard is aligned with GHS and BS 5609, opening companies up to possible liability if containers are not properly labeled.

The real takeaway here is that there are numerous things to consider in choosing materials for chemical container labeling - and a lot of options. Suppliers who are well-versed in the application requirements can assist you in choosing label materials that will perform as expected, protect workers and the public, and limit liability.