Paper/Paperboard/Corrugate Tests

An estimate of the maximum difference in results that can be expected to be obtained 95% of the time when measurements are done under the requirements listed below. 1. Within a single laboratory. 2. On the same material. 3. Using the same equipment. 4. By the same person. 5. Under the same environmental conditions. 6. Within a short time frame.

An estimate of the difference in results that can be expected 95% of the time when comparing tests performed by two laboratories, assuming the measurements are done under the requirements listed below. 1. Apparatus used is properly calibrated. 2. Environmental conditions are appropriately controlled. 3. Personnel are correctly trained.

The number of digits that are known with some degree of certainty, that carry meaning. Avoid giving the appearance of greater precision than the test device can provide.

errors produced by the procedure.

1) User Requirements 2) PKG Specification 3) PKG Evaluation 4) PKG Implementation

• Standard conditions: 23oC (73.4oF), 50% RH. • Sample near center and edges of roll or sheet. • Take into consideration whether samples are machine direction (MD) or cross direction (CD). • Document samples.

• Influenced by ... 1. Process controls. 2. Moisture content. 3. Furnish. • Has significance to ... 1.Stiffness. 2. Machinability Machinability. The ease with which a product, package, or material moves through a production line and produces a good quality package. 3) Compression resistance. 4) Volume occupied in use. 5) Material specifications. 6) Purchasing.

• Caliper of a material refers to its thickness. • Paperboard commonly specified by points in U.S. • Paper is commonly specified by basis weight in U.S. • Measurement Technique. Automatic Micrometer. Sample near center and edge. Measurements are made along the cross direction due to higher variation than machine direction. Measurements are averaged. In addition, high and low measurements often reported.

• U.S. units are \"points.\" 1 point = 0.001 inch. 1 point = 1 mil. 1 point = 0.0000254 m. 1 point = 25.4 μm. 1 point = 25.4 microns. • International units are mm or microns. 1 mm = 1000 microns. 1 mm = 1000 μm. 1 mm = 0.001 m. 1 mm = 0.1 cm. 1 mm = 39.37 points.

covers thickness of paper, paperboard, and combined board.

• Weight per unit area. • The most common way to specify paper and some paperboards. • Basis for pricing paper. Prices are expressed in dollars per ton. Area per ton depends on the basis weight. • Basis weight is used in the U.S. • Grammage is used every where else, except U.S. • TAPPI T410 covers grammage and basis weight. • Need at least 8\" x 10\" sample. • Specialized basis weight scales use a 12\" x 12\" sample. • Specialized grammage scales (TMI) use 20cm x 25cm samples. • Analytical balance can be used. • Grammage and basis weight are very key concepts for the packaging professional. • Basis weight for paper refers to the weight in pounds of a standard ream of 500 sheets of paper. Each sheet measures 24 inch x 36 inch. Total of 3,000 ft2 of paper in a 500 sheet ream. Typical range of basis weight for paper is 16 to 90 lbs. • Basis weight for paperboard (and container board used in corrugated board) refers to a standard ream of 500 sheets of paperboard. Each sheet measures 12 inch x 24 inch. Total of 1,000 ft2 of paperboard in a 500 sheet ream. Typical range of basis weight for paper is 26 to 90 lbs. 1,000 ft2 is also referred to as MSF (or msf ). • Grammage refers to the weight of paper or paperboard in grams per square meter. Expressed as gsm, or g/m2. Tissue paper has grammage of 12 - 30 g/m2. Typical range for paper is 30 to 100 g/m2. Typical range for paperboard is over 224 g/m2. In the range 100-224 g/m2 products may be paper or paperboard. Useful conversions. 1 lb = 454 g (453.6 g). 1 in = 0.0254m. 1 ft = 12 in = 0.3048m. 1 ft2 = 0.0929m2.

• Density is the ratio of mass to volume. • Density affects almost all properties of paper. • Paper and paperboard are hygroscopic, so their densities vary with moisture content. • Paper density is always specified at a given moisture content. • Apparent density (D) of paper or paperboard is the weight (M) divided by the volume (V), or the grammage divided by the thickness (t). D = M/V = G/t • Typical apparent densities range from 0.5 g/cm3 for bulky papers to over 1 g/cm3 for heavily bonded sheets like glassine. • All papers are less dense than cellulose alone, which has a density of 1.5 g/cm3, so all papers contain some void space. • Note that apparent density is generally specified in g/cm3. Example: What is the apparent density, in g/cm3, of paper that has a grammage of 150 g/m2 and a caliper (thickness) of 0.2 mm? D = G/t D = (150 g/m2) / (0.2 mm x 1 m/1000 mm) D = (150 g/m2) / (0.0002 m) D = 750,000 g/m3 D = (750,000 g/m3) x (1 m / 100 cm)3 D = 0.75 g/cm3

• TAPPI T402 covers standard conditioning and testing atmospheres for paper, board, pulp handsheets, and related products. • Standard TAPPI conditions for testing are 23oC±1oC (73.4oF±2oF) and 50%±2.0% RH. • Samples should first be precondition. 10-35% RH and 22-40oC. Corrects for the hysteresis effect of paper. 1 hour for single sheets. 16 hours for sealed boxes and shipping containers. ASTM D685 recommends 24 hours for boxes and containers. • Samples then have to be in standard TAPPI conditions long enough to come to equilibrium with the atmosphere. 4 hours for paper. 8 hours for paperboard and unsealed boxes. 16 hours for sealed boxes and shipping containers

• Paper industry generally expresses moisture content on the wet basis, unlike wood that uses the dry basis. Considered more convenient when calculating the required amount of pulping chemicals. Wet basis moisture content is always less than 100%. ????? = 100% × ?????? − ???? ?????? • What is the moisture content (wet basis) of a sample of paper if its initial weight is 150g, and its weight after drying is 100g? ????? = 100% × ?????? − ???? ???? ????? = 100% × 175? − 80? 175? ????? = 54.3% • If the sample had been wood and moisture content was calculated on a dry basis, the answer would be 119%. • Ideal moisture content range for paper is 3% to 7%. Below 3% paper becomes brittle. Above 7% paper loses stiffness, becoming soft and mushy. • Moisture affects all properties of paper; however, it does not affect all properties equally. Tensile strength and stiffness decreases with increasing RH. Tear resistance and folding endurance increase with increasing RH. Moisture Content (Cont.) • Curling can occur due to moisture absorption/desorption of fibers. Amount of curling depends on fiber orientation, with more pronounced orientation having more curl. Moistening one side of a piece of paper will cause it to curl around an axis parallel to the machine direction with the wet side out. Curling will subside as water soaks through the paper. Labels for bottles are designed with the machine direction horizontal, to counter the tendency of the labels to curl.

Examples: • Papers 20 - 120 lbs/3000 ft2 = 32.5 - 195 g/m2 • Paperboards 26 lbs/1000 ft2 = 127 g/m2 42 lbs/1000 ft2 = 205 g/m2 90 lbs/1000 ft2 = 439 g/m2