How Professionals Waterproof Cardboard
Because cardboard is paper, it is susceptible to humidity and water damage. Continual exposure to water causes the cardboard to become a soggy mess. In order to broaden the capability of cardboard and to fulfill water-resistant requirements from customers, manufacturers have created various ways of applying a waterproof coating to their products. These include laminating cardboard with plastic film, curtain coating (spraying) an exterior plastic coating to the cardboard, impregnating 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 wax blend. Using wax cascading methods involves the actual pouring of the wax over the cardboard as its passing through the assembly line in a vertical manner, allowing 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.
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.