Making Corrugated/Cardboard Containers Waterproof
How it’s done
Cardboard is made of paper, which makes it susceptible to water damage. If cardboard is continually exposed to water, it begins to absorb the water and fall apart. To broaden the capability of cardboard, manufacturers have created various ways of applying a waterproof coating. Not only does this help the cardboard, but it also ensures that the products they ship will stay dry.
The Waterproofing Method
Every piece of cardboard does not necessarily get coated with wax. When spraying the cardboard, only the outer sheet of the corrugated box is coated in the paraffin wax. If the cascading method is applied, then the wax is poured over the cardboard as it is vertically passing through the assembly line allowing for the wax to cover more by passing through the corrugated layer and exterior flat sheets. The most effective method is wax dipping though by physically dipping the cardboard into the wax.
Other Methods
There is also an adhesion process that can be used to apply a waterproof film that is laminated to the cardboard. Typically, this is performed to only one side of corrugated cardboard. This does not allow for full protection though from water or damp environments. The film that is being laminated is usually a low-density polyethylene. An added contingency is the inclusion of vapor corrosion inhibitors that can be sprayed on paper and cardboard. These provide water protection for any metal contained within the cardboard.
Applications of Polyethylene Plastic
Polyethylene is the most common plastic produced in the world and it comes in a wide variety of physical properties. For packaging, it is preferred as a soft and pliable film. Polyethylene offers the lowest softening point of the basic packaging plastics. This low softening point results in lower processing energy costs thus making it more economical. There are three types of polyethylene commonly used in the packaging industry: High-Density Polyethylene (HDPE), Low-Density Polyethylene (LDPE), and Linear Low-Density Polyethylene.
Perishables
“Paperboard is a versatile carton material that demands a barrier treatment when used in aggressive environments. Corrugated boxes are a staple solution for the shipping and storage of fresh produce and other perishables as well as environmentally sensitive materials. For longstanding or emerging applications, Michelman has the trusted brands of barrier and functional coatings to cover the gamut of performance requirements for paperboard and corrugated.” (2017 Michelman, Inc.)
The Future
With recent developments in waterproofing, cardboard may eventually render previous applications obsolete. There has been a developmental breakthrough with a biodegradable waterproof coating. The coating is made from the pulp of sugar cane and could change the entire industry of paper coating. The process for creating this coating involves removing the cellulose from the sugar cane and putting it through a fermentation process that preserves the lignin. The lignin is the part of the cellulose that is waterproof. Typically, this is destroyed in the paper making process using tree-based pulp. This new process with sugar cane would allow for the recycling of treated cardboard, something that is not possible with conventionally coated cardboard. This innovation would be revolutionary in reducing the “billions of tons of harmful cardboard waste found in landfills worldwide.”
References
Burke, Alex. "eHow." 1 January 2017. Leaf Group Ltd. 10 March 2017. <http://www.ehow.com/how_5970273_make-waterproof-sign.html>.
Michelman, Inc. Printing & Packaging. 1 January 2017. 10 March 2017.
<http://www.michelman.com/Printing-&-Packaging/Paper-Converting-&-Corrugated/Perishables/>.
U.S. Packaging. "Polyethylene Plastic." 8 February 2014. U.S. Packaging and Wrapping LLC. 10 March
2017. <https://packagingblog.org/2014/02/08/polyethylene-plastic-packaging-applications/>.
https://www.gwp.co.uk/coatings/board-coatings/waterproof-cardboard-coating/
