The Sutherland Rub Test

The placement of printed labels directly on pharmaceutical container and package systems has been an accepted practice for many years. Typically, these labels provide critical product information for the patient or end-user. Ensuring the integrity of these labels is critical. Integrity is best defined as the ability for the label to remain legible. Damage caused by abrasion, which can compromise legibility to the printed label, can occur during shipment, storage, handling, or by the end-user. This abrasion can result in significant degradation in product appearance and legibility of the product information that is printed on them.

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The ASTM prescribed test method to evaluate the abrasion resistance is D &#;Standard Practice for Abrasive Resistance of Printed Materials by the Sutherland Rub Tester&#;. Alternatively known and abbreviated as the &#;Sutherland Rub Test&#;, this test uses an instrumented specifically designed simply for this test.

The Sutherland Rub Test can determine the amount of scuff or abrasion damage that may occur to printed materials during shipment, storage, or handling. This test procedure can simulate the effects of human use in continuous contact or dual surface abrasion on any type of printed material.

The Sutherland Rub Test is performed by attaching a label to the device while a similar sample label is attached to a weight. The two samples are then rubbed against one another at a controlled speed for a predetermined number of cycles. Once the rubbing stops, the samples are visually inspected to see if the ink has worn off or not. This helps to determine if printing is durable enough to withstand the expected conditions it will face in the marketplace. The ASTM procedure does not assign a specification (pass/fail) to the test procedure. The testing is typically performed at a number of varying stroke points (number of rubs) and evaluations and comparisons are made based upon the amount of ink that has worn off, smeared or becomes non-legible.

Why is the Sutherland Rub Test Important?

Ensuring legibility of printed labels is paramount in various industries, especially in the pharmaceutical and food sectors. Abrasion damage to these prints can lead to crucial information becoming unreadable, which may pose severe risks to the end-users. By conducting the Sutherland Rub Test, manufacturers can ensure that their products' labels remain intact and legible throughout their lifecycle, from production to end-user handling.

The test also saves companies from potential recalls or legal issues related to unreadable product information or compromised product integrity. It’s a small yet significant step towards maintaining quality and safety standards.

The team at CS Analytical has years of experience performing the Sutherland Rub Test on a wide variety of label types and configurations. While often overlooked, it is critical that when thinking about developing a comprehensive package system qualification program, tests such as The Sutherland Test are not ignored or overlooked.

Rub is the process of moving one surface in contact with another. This can lead to abrasion (wearing away of, or deforming the surface), smudge, scratch (breaking through to the surface) or mar (deformation that does not break through).

The complexity of wear processes has led to the development of numerous standard test methods and test apparatus. Correlation between these methods is not generally possible as each employs a different rub or abrasion technique, although materials are often ranked similarly.

Smithers has a wide range of testing facilities and equipment including the Sutherland Rub Tester, the Finger Rub Abrasion Tester, the Smithers Rub Tester, the Taber Abraser, the Sheen Motorised Scratch Tester, the Satra Rub Tester and the Crockmeter.

Sutherland Rub Tester

This is commonly used to determine the amount of scuff or abrasion damage associated with transit shipment, storage, or handling of printed packaging.

The Sutherland Rub Test is performed by attaching a label to the device while a similar sample label is attached to a weight. The two samples are then rubbed against one another at a controlled speed for a predetermined number of cycles. In contrast to the rotary Smithers Rub Tester (see below), the Sutherland Rub Tester employs a reciprocating arc motion, which gives an essentially linear, directional action. On completion, the samples are visually inspected to check for ink transfer.

The Sutherland Rub Tester conforms to ASTM D &#; Standard Practice for Abrasion Resistance of Printed Materials.

Finger Rub Abrasion Testing

The newly developed Finger Rub Abrasion Tester is designed to simulate abrasion of markings and lettering caused by the rubbing of fingers and hands following BS EN -2-70:.

The sample is rubbed by a piston which acts as a simulated finger. To obtain reproducible conditions of friction, a piece of fabric is placed between the piston and the surface under test.

This fabric may either be dry (dry test) or soaked with a specified test liquid, such as artificial perspiration if the test is intended to cover the influence of fluid contamination as may occur in normal use (wet test).

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On the completion of a set number of cycles, the test sample is examined for signs of abrasion or wear, including the legibility of variable data and data matrix codes on printed labels.

Smithers (PIRA) Rub Tester

The Smithers (PIRA) Rub Tester rubs two surfaces against each other (face-to-face) in the same plane, at the same speed, under a constant rubbing pressure.

The rub test equipment used by Smithers supports with evaluating the rub resistance of labels and general printed matter, and can also be used to evaluate color transfer from printed or coated surfaces during rubbing.

The Smithers Rub Tester conforms to British Standard BS .

Taber Abraser

The Taber Abraser is primarily used to evaluate the resistance of surfaces to rubbing abrasion. Specimens are mounted on a rotating turntable and subjected to the wearing action of two abrasive wheels, which are applied at a specific pressure. The severity of the test can be altered by using different wheels under different loads. The end point is either a visual change in appearance or a weight loss associated with material removed by abrasion.

• ASTM D covers transmission haze of packaging films.
• Tappi Standard T476 covers the abrasion loss of paper and board
• BS covers the determination of resistance to abrasion applicable to paints and varnishes
• BS ISO/IEC -2 covers the resistance to surface abrasion of ID cards.

Sheen Motorised Scratch Tester

A test panel is withdrawn under a constant weighted 1mm tungsten carbide ball-ended needle at a speed of 3.4cm/second using a Sheen 705 mechanised Scratch Tester satisfying the requirements of BS Part E2 /ISO . Failure of the surface coating is examined visually and by electrical surface resistance when the underlying substrate is electrically conductive.

Coating failure under a given needle profile/weighting is related to coating-substrate adhesion, mechanical properties of substrate and coating, coating thickness, internal stress in coating and friction between stylus-tip and coating. The practical scratch adhesion value of a coating is defined as the lowest critical load at which the coating fails.

Satra Rub Tester

The Satra rub tester is a circular rub fastness tester which can also be used for testing the rub/abrasion resistance of inks on printed films, such as plastic carrier bags, under dry and wet conditions.

The machine has a rotating head holding a circular felt pad which is applied to the sample under a defined load.

The rub or abrasion resistance is determined by the extent of damage to the sample material or by the extent of color or print transfer to the felt pad, using a standard scale where necessary.

The felt pad can be soaked in a variety of solutions to determine the wet rub resistance of the sample material.

Crockmeter

The Crockmeter is used to assess the transfer from the surface of colored materials to other surfaces by rubbing. The machine takes its name from the term 'crocking' meaning the transfer of coloring matter or other substances from the test sample to a wet or dry cloth rubbed against it under the action of an artificial finger.

The Crockmeter is used in testing against ASTM F and International Standard ISO 105-X12.