Making Cardboard Waterproof

  Reviewed by: Michelle Seidel, B.Sc., LL.B., MBA
  Written by: Alex Burke      Updated October 20, 2018
top view of an empty cardboard box

You need your business parcels to reach their destinations in the condition you sent them, regardless of weather conditions. That's where treated cardboard comes in handy. Continual exposure to water and excessive humidity causes cardboard to lose its rigidity. This exposure decreases its strength and skews its Edge Crush test (ECT) rating, which is something you and your clients can't afford.

To broaden the capability of cardboard and fulfill water-resistant requirements from customers, packaging manufacturers have created a few ways of waterproofing their products. These include laminating cardboard with plastic film, spraying an exterior plastic coating to the cardboard, impregnating the cardboard with a wax coating or using a method called cascading, which saturates the cardboard with a hot wax substance. Wax is a petroleum-based product.

Wax Waterproofing Methods

Wax impregnation does not necessarily happen to every piece of the cardboard. For example, a corrugated cardboard is made up of at least three pieces of board, a corrugated sheet sandwiched by two flat sheets. In the case of corrugated cardboard, it may only be the outer flat sheets that are impregnated by paraffin wax or a wax blend. Using wax cascading methods involves the actual pouring of the wax over the cardboard as it's passing through the assembly line in a vertical manner. This process allows the wax to pass through the corrugated layer and the exterior flat sheets, thus covering more of the board. Wax dipping goes a step further than wax cascading by actually dipping the cardboard into the wax preparation.

Other Waterproofing Techniques

The laminating of waterproof film to cardboard is an adhesion process. Generally only one side of corrugated cardboard is laminated, which does not allow for full protection from water or damp environments like refrigeration units. The film being laminated is usually a low-density polyethylene. Vapor corrosion inhibitors can be sprayed on paper and cardboard, too. This provides corrosion or water protection for metal items contained inside the cardboard.

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A New Waterproof Product

Recent developments in waterproofing cardboard may soon render previous applications obsolete. The development of a biodegradable waterproof coating made from the pulp of sugar cane could change the face of the paper coating industry. The process involves removing the cellulose from the sugar cane and putting it through a fermentation process that preserves the lignin, which is the waterproof part of cellulose. Conventional paper-making methods destroy the waterproof characteristic of lignin in tree-based paper pulp. The new process would allow the recycling of treated cardboard, which is not possible with conventionally coated board. The result would be a huge reduction in the billions of tons of harmful cardboard waste found in landfills worldwide.

About the Author

Alex Burke holds a degree in environmental design and a Master of Arts in information management. She's worked as a licensed interior designer, artist, database administrator and nightclub manager. A perpetual student, Burke writes Web content on a variety of topics, including art, interior design, database design, culture, health and business.

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