Paperboard is a thick, paper-based material used for packaging. In the mid-1800s, with the introduction of the Fourdrinier Machine, mass production of paper and certain forms of paperboard were introduced. Soon after, an inexpensive method for mass-producing paperboard folding cartons was developed.
Today, there are several different kinds of paperboard that possess unique characteristics, making each type suitable for different requirements and needs. Paperboard used for folding cartons for delicate items like cereal or cosmetics is crucial for protecting the product. Whereas paperboard used for display, such as on your package of razors, is crucial for its strength.
What is Paperboard?
Paperboard is the broad name that refers to different qualities, or grades, of paper-based packaging material. It is generally thicker than writing paper. Grades differ from one another based on what percentage is produced from recycled content, what surface coatings it has and what color it is. Below are four main grades.
Solid Bleached Sulfate (SBS)
Bleached paperboard or solid bleached sulfate (SBS) is a premium paperboard grade that is white in color. In order to be considered SBS, the finished product contains no more than 20 percent recycled materials. The remaining 80 percent must be composed of freshly-harvested woodchips that are chemically processed and bleached. The bleaching process gives SBS its signature white color, both inside and out.
SBS is used to package everyday products, including food and beverages, cosmetics and pharmaceuticals. In order to print marketing and product information on the paperboard packaging’s surface, most SBS is coated with a naturally-occurring mineral called kaolin clay to improve its printing surface. If the packaging is intended for frozen foods or liquids, it may also be coated with a very thin plastic lining for wet strength protection.
Coated Unbleached Kraft Paperboard (CUK)
Similar to SBS, clay natural Kraft (CNK®) or solid unbleached sulfate (SUS®) paperboard (two variations of CUK) contains no more than 20 percent recycled material. However, when the 80 percent freshly-harvested woodchips are processed, they are not bleached and the paperboard’s bottom and inside layers remain the natural brown color.
Although the inner layers are brown in color, unbleached paperboard’s surface is still treated the same as bleached paperboard in order to create a printable and wet-resistant surface.
Uncoated Recycled Paperboard (URB)
Uncoated recycled paperboard, a multiply material, is produced from recovered paper-collected from paper manufacturing and converting plants and post-industrial sources. During production, the surface is not coated for printing purposes. However, depending on the packaging’s end purpose, a top layer of white recovered fiber can be added or the material can be mass dyed to desired colors.
Coated Recycled Paperboard (CRB)
Coated recycled paperboard is produced from 100 percent recovered paper just as uncoated paperboard is. However, to improve the printing surface, it is typically coated with a thin layer of kaolin clay (the same mineral used with SBS and SUS paperboard grades) in addition to a layer of white recovered fiber. Manufacturers choose coated recycled paperboard over uncoated when the packaging will be used for products that have marketing and writing on the outside.
What Kinds of Products are Made from Paperboard?
Paperboard is used to package various products. The grade of paperboard used depends on the products’ needs and requirements.
Major market segments that use solid bleached sulfate:
- Medical packaging
- Hot and cold paper cups
- Milk and juice gable top cartons
- Aseptic drink boxes
- Cosmetic and perfume packaging
- Frozen food packaging
- Candy boxes
- Stand up displays
Major market segments that use coated unbleached Kraft paperboard:
- Frozen food packaging
- Pharmaceutical packaging
- Beverage carrying containers
Major market segments that use uncoated recycled paperboard:
- Composite cans and fiber drums
- Coated Paperboard
Major market segments that use coated recycled paperboard:
- Soap and laundry detergent packaging
- Cookie and cracker packaging
- Paper goods packaging (facial tissue and napkins)
- Cake mix packaging
- Cereal boxes
- Other dry food packaging
Why Use Paperboard?
Performance and Flexibility
Paperboard offers strength and durability to house products of all shapes and sizes, while also offering flexibility. Easy to cut and form, it is both lightweight and strong, which makes it ideal for packaging.
Paperboard packaging is appealing to consumers. Due to processes that make the surface printer-friendly and the ability to either bleach it white or dye the board to desired colors, companies can market their products with bright, fresh writing and images. This is key, as packaging catches consumer’s eyes on store shelves and Internet ads.
Paperboard packaging is made from a renewable resource, trees, that are replanted to ensure a sustainable supply and recovered paper. The U.S. grows more wood than it harvests. There are 20 percent more tress in the U.S. now than there were in 1970. According to the U.S. Environmental Protection Agency (EPA), paper and paperboard packaging, accounts for nearly three-quarters of packaging materials recovered for recycling in the U.S. That is more than any other packaging material.
How is Paperboard Made?
The first step in the process is to make pulp. Pulp can be made from either virgin fiber, which are wood chips, or from recycled paper products.
Wood chips (virgin fiber) are cooked using a chemical process in essentially a pressure cooker known as a digester. The wood fiber is separated into cellulose fibers, lignin (the wood glue that holds the tree together) and other substances such as sugars. Cellulose is an essential building block in the cell walls of trees and plants, helping to make them strong. The pulp is then washed to clean it and separate it further from the other tree components. After the pulp is washed, it is screened for further cleaning.
For mills using recycled materials, pulp is made by mixing the recovered fiber with water in what resembles a large blender called a repulper. In the repulper, the pulp is separated to create individual fibers in a slurry. From there, the pulp is washed and screened to further separate the fiber from other debris like dirt.
The pulp then needs to be formed into a sheet on the paper machine. At the wet end of the paper machine, the pulp flows onto a moving endless belt with a screen to filter out water and form a web. Further down the line, in the press section, the pulp, which looks like a sheet, goes through several presses to further remove excess water. At this point the web of material still must shed water, so it passes into a dryer. The dryer is a large cylinder and uses steam to dry the pulp. The wet web of pulp is pressed against the cylinder tightly to dry it through evaporation.
Next, it must be calendered, which means the sheet passed between steel rollers to improve its smoothness and adjust its thickness. Finally, in some instances, coatings are applied to the print side of the paperboard. Then the paperboard is reeled so it can be shipped or cut to customer specifications.