Deposition Standard
Quantity measurement of applied chemical layers determines the functional and visual properties of treated paperboard and flexible films. Referred to as coating weight, this value represents the dry mass of adhesive, clay, polymer, or wax applied per unit area of the substrate. Precise control of this parameter prevents issues like ink bleeding or insufficient barrier performance during printing and sealing operations.
Measurement Method
Determination of this value involves both direct gravimetric analysis and indirect non-destructive techniques. Standard industrial practice uses the weigh-strip-weigh method, where a coated sample of known area is weighed, stripped of its coating using a solvent, and weighed again to compute the difference. Alternatively, online sensors utilize infrared absorption or x-ray fluorescence to monitor the thickness continuously as the web moves through the coater.
These real-time measurements allow immediate adjustment of the doctor blade or metering roll to keep the dry laydown within the narrow tolerances demanded by high-speed converting lines.
Functional Threshold
Insufficient application of the coating layer leads to poor barrier performance and inadequate adhesion during lamination. Conversely, excessive material application increases production costs and can cause cracking when the paperboard is folded along score lines. Correct balances must be maintained to satisfy both the aesthetic print requirements and the mechanical conversion limits of the finished carton.
