Paper and paperboard materials are available in rolls or sheets and are used for writing, printing, packaging, and many other applications. Categories include commercial paper, industrial paper, and paperboard. Commercial papers are produced as a single layer on a fourdrinier. Types include text and cover stock, graphic arts and fine arts papers, currency stock, newsprint, packaging and barrier papers, and tissue and sanitary papers. Industrial papers meet strict technical requirements. They are often produced for a very specific purpose. Types include coated and coating base papers, saturated and saturating base papers, filtration and separation media, absorbent and blotting media, electrical insulation papers and separators, thermal insulation and fireproofing papers, gasketing and sealing materials, and structural and composite papers. Paperboard is a broad category of paper and paperboard products with a high basis weight and high density. There are three basic types of paperboard: linerboard, corrugating medium, and solid bleached paperboard.
Paper and paperboard materials such as base papers often undergo secondary processing before use. This additional processing is incorporated into the initial production process, or completed off-machine. There are many secondary processes for base papers. Examples include sizing, calendaring, glazing, saturation, coating, folding, corrugating, perforating, slitting, and sheeting. Sizing is the process of lightly coating one or both surfaces of a paper with a starch solution to enhance surface properties. Calendering presses paper and paper products between two rolls under high pressure. As paper density and surface smoothness increase, porosity and thickness decrease. Glazing produces similar results, but uses a moving ball to apply high pressure to only one side of the paper. Saturation is an immersion process in which paper is fully wetted - typically with a latex dispersion - and subsequently dried. Coating applies one or more layers of material to one or both surfaces of a paper. Perforated papers and paperboard products have minor cut marks in the cross-roll direction. Sheeting cuts a roll of paper into sheets of uniform dimension.
Selecting paper and paperboard materials requires an analysis of base sheet physical properties, mechanical properties, bulk properties, paper color, and special features. Basis weight, thickness, width, and length are important base sheet physical properties to consider. Mechanical properties include both tensile strength and tear strength. Dielectric strength, electrical resistivity, thermal conductivity, and maximum use temperature are examples of bulk properties. The color of paper and paperboard products is determined by the position in a three-dimensional coordinate system in which one axis is the paper’s brightness from 0 to 100%, another axis is the green/red direction, and the third axis is the blue/yellow direction. Brightness, opacity, and clarity are important considerations. In terms of special features, some paper and paperboard products are designed to resist flame, smoke, chemicals, ultraviolet (UV) light, or tampering. Others are hydrophilic, hydrophobic, recyclable, tamper-evident, or designed for anti-counterfeiting applications.
Paper and paperboard materials are made of wood pulp; plant, polymer, or inorganic fibers; and non-fibrous materials. They carry approvals from organizations such as the Association of the Pulp and Paper Institute (TAPPI) and differ in terms of applications. Commercial markets for paper and paperboard products are divided into school, home and office products (SHOPA); packaging and material handling applications; interiors and furnishing, and apparel and clothing. Industrial markets include agriculture, chemical processing, electrical and electronics, laboratory, medical, and biopharmaceuticals. Paper and paperboard products for transportation and building and construction applications are also available.