By Judy Arvan, Sr. Process Engineer,
Graphic Packaging International
The type of paperboard you choose can make or break a product—literally! Good thing for us, there are a number of board properties we can evaluate to understand how the different types will function—and which is the right choice for the job at hand.
I teach these properties twice per year to industry newcomers at PPC’s Folding Carton Boot Camps. We go into much more detail there, but here are the basics:
Paperboard Properties and Definitions
Basis Weight
How heavy is the board? Basis weight measures its weight per unit area. It’s generally calculated using pounds per 1,000 square feet (lb/MSF) or pounds per 3,000 square feet (lb/3MSF).
Brightness
If the customer wants a brilliant board, consider brightness. Technically, brightness is the amount of reflectance of a specific wavelength, 457 nanometers. Whiteness measures the reflection of all wavelengths of light across the visible spectrum; brightness measures the shade of the paper from blue to yellow.
Caliper
This is the thickness of the paperboard, generally measured in thousands of an inch. It’s is also referred to as “points of caliper”.
Curl
Curl is the tendency of paper, on its own, to warp or bend. Usually we want to limit curl as much as possible. Keep in mind that humidity influences curl significantly.
Glueability
Whether it is empty or full to the brim, packages need to hold their shape. Glueability determines the speed and strength of the bond created between applied adhesive and the paper surface
The strength and quality of a package’s glueability is maintained through rigorous testing protocols. Manufacturers can find how well the connection lasts in extreme conditions through the cold dextrin glue test and the hot melt glue test.
Moisture Content
Moisture content is the amount of water the paperboard contains. It is represented in a percentage (%) based on the paper’s total weight.
Plybond Strength (ZDT or BRDA)
This is the measurement of the paper’s internal strength, determined by the amount of force needed to pull the sheet apart. Testers use the Z-directional tensile strength test, which is pulling the paper apart perpendicular to its surface.
Smoothness
Smoothness is more than the lack of irregularities on a paper’s surface. It is the measurement of the evenness, lack of contour, or roughness.
Smoothness is rated on the macro level by the Sheffield Smoothness Gauge and the micro level through the Parker Print Surf. Both measurements are found by an air leak test which is the time it takes for air to seep between a smooth glass plate and the paper sample.
Taber Stiffness MD & CD
The Taber Stiffness Tester evaluates the bending resistance of paperboard which is its stiffness and resiliency. It is determined by measuring strips cut in the Machine Direction (MD) and the Cross Direction (CD) of the paperboard web. The ratio of these qualities (MD/CD) is the paper’s stiffness ratio.
These are just a few properties you can test to ensure that you’re using the best quality paperboard possible. Simply reviewing a few features can ensure that your customers keep coming back for your packaging time and again because of its superior benefits.
For more ways to improve your packaging and design, come to PPC’s Folding Carton Boot Camp, May 19-20 in Springfield, MA. The workshop is ideal for anyone new to cartons as well as non-plant personnel with limited experience outside a single plant operation. Industry thought leaders teach the whole converting process, from sustainable forest to the store shelf. I hope to see you in there!