Does TAPPI T816 measure kinetic COF as well as static COF?

No. TAPPI T816 measures static COF only — the force required to initiate sliding. For kinetic COF on paper products, some laboratories use ASTM D1894 procedures adapted for paper, though this is not a standard practice under TAPPI T816.

How many specimens does TAPPI T816 require?

TAPPI T816 requires a minimum of 10 specimens per test set, which is more than the 5 required by ASTM D1894. The higher specimen count reflects the greater natural variability of paper surfaces compared to extruded plastic films.

Why is conditioning so important for paper COF testing?

Paper is hygroscopic: its surface energy and fiber structure change with moisture content. A 10% change in relative humidity can significantly alter the static COF of uncoated paper. TAPPI T816 requires 24 hours at 23°C / 50% RH to stabilize specimen moisture before testing.

What surface configurations does TAPPI T816 cover?

TAPPI T816 can be used for paper-to-paper, paper-to-metal, and paper-to-other-substrate configurations. The test report must specify the surface configuration used, since COF values differ significantly between configurations.

Can the MXD-02A test corrugated board to TAPPI T816?

Yes, provided the corrugated board specimen can be held flat on the test bed without significant curl or deformation. For heavily warped corrugated specimens, a specimen fixture or weight-assisted hold-down may be needed. Contact KHT for guidance on fixture options.

Is TAPPI T816 the same as TAPPI T549?

No. TAPPI T816 uses the horizontal-plane sled method and reports static COF directly as a force ratio. TAPPI T549 uses the inclined-plane (slide-angle) method and reports the angle at which sliding begins, which is then converted to a COF via the tangent function. The two methods can give different results on the same material.

TAPPI T816 — Coefficient of Friction of Paper and Paperboard

What Is TAPPI T816

TAPPI T816, formally titled 'Coefficient of Static Friction (Slide Angle) of Packaging and Paperboard (Horizontal Plane Method),' defines a test procedure for measuring how much force is required to initiate sliding between two paper surfaces or between a paper surface and a reference surface. The result is expressed as a dimensionless static COF value. Unlike ASTM D1894 and ISO 8295, which measure both static and kinetic COF, TAPPI T816 focuses exclusively on static COF — the breakaway friction relevant to stack stability, pallet load behavior, and bag-in-box anti-slip performance. The standard is maintained by TAPPI's Physical Properties subcommittee and is widely used in the containerboard, carton, sack, and flexible paper packaging industries across North America.

Scope for the Paper Industry

TAPPI T816 applies to paper, paperboard, corrugated board, and related cellulosic sheet materials. Typical applications include: measuring the anti-slip coating performance of sack kraft and heavy-duty paper bags, evaluating the interlayer friction of corrugated board pallet loads, quality-checking the clay or polyethylene coatings on folding cartonboard, and assessing the machine-direction versus cross-direction friction asymmetry of tissue and towel products. Because paper COF is strongly influenced by surface roughness, coating weight, moisture content, and calendering history, TAPPI T816 places strict requirements on specimen conditioning before measurement. The standard does not apply to plastic-coated papers or laminates where the plastic surface dominates the friction behavior; such materials should be tested to ASTM D1894 or ISO 8295.

Horizontal Plane Method

TAPPI T816 uses the horizontal-plane sled method: a weighted sled is pulled across a flat, stationary specimen by a constant-speed drive connected to a force transducer. The sled has a mass of 200 g and a flat base. The test measures the peak horizontal force required to initiate sled movement, which is the static friction force. This force is divided by the normal force (sled weight × g) to yield the dimensionless static COF. The horizontal-plane method is preferred over the inclined-plane (slide-angle) approach because it provides a direct force measurement rather than inferring friction from the angle at which a sample begins to slide. Horizontal-plane instruments also allow a wider range of sled masses and surface configurations to be tested under controlled conditions.

Sample Conditioning Requirements

Paper and paperboard are hygroscopic: their surface energy, fiber structure, and any applied coatings all change with moisture content. To ensure reproducible results, TAPPI T816 requires conditioning specimens at 23 ± 1°C and 50 ± 2% relative humidity for a minimum of 24 hours before testing — stricter than the 40-hour plastic film conditioning in ASTM D1894. Specimens must be handled with clean cotton gloves after conditioning to avoid contamination from skin oils. Testing must take place in the same conditioned environment or as quickly as possible after removal from the conditioning chamber. If the laboratory humidity deviates from 50% RH, results should be flagged as non-standard. Some paper grades, particularly those with moisture-sensitive coatings, may require longer conditioning periods; this should be agreed upon between buyer and seller.

Procedure and Reporting

Condition at least 10 specimens per test set for 24 hours at 23°C / 50% RH. Specimens should be cut in both the machine direction (MD) and cross direction (CD) if directional COF is relevant to the application. Place the bed specimen flat on the test surface. Mount the sled face-down on the sled specimen. Attach the sled to the load cell via a horizontal, inextensible line. Initiate the drive and record the peak force at first slip (static COF event). Do not re-use specimens. Repeat for all 10 specimens. Report: mean static COF, standard deviation, specimen direction (MD or CD), material description and lot number, conditioning temperature and humidity, and any surface configuration notes (e.g., paper-to-paper vs. paper-to-metal). The standard recommends reporting results separately for MD and CD when anisotropy is expected.

How MXD-02A Meets TAPPI T816

The MXD-02A meets the apparatus requirements of TAPPI T816. It uses the standard 200 g sled and a horizontal test bed. The drive speed can be set to the low, constant velocity appropriate for paper friction measurements, and the 0–5 N load cell with 0.001 N resolution provides accurate peak detection for the relatively sharp static COF events typical of paper surfaces. The instrument's PC software records the full force-displacement curve, allowing automatic identification of the static peak without operator subjectivity. Test reports include all required fields: specimen identification, conditioning details, mean and standard deviation of static COF, and test date. The selectable 150 mm stroke provides sufficient travel for paper specimens that may show a delayed or broad static peak compared to plastic films.

TAPPI T816 — Coefficient of Static Friction of Packaging and Paperboard (Horizontal Plane Method)