Textiles are used in a variety of medical applications, including dressing and treating wounds, a wide variety of suture materials, textile-based implant structures (for example, hernia net implants) and surgical drapes and clothing. Materials used include natural and synthetic fibers, together with breathable films and material combinations. The many different products and materials used in this area call for a wide range of materials and function tests.
To avoid the problem of individual fibers of gauze bandages catching on the roll below and preventing reliable unrolling, it is necessary to determine the force required to unwind the bandages from a roll. For this, a ZwickRoell materials testing machine with a nominal force 10 kN is used, together with a motor-driven unrolling unit. The sequence is controlled by a specially adapted program from ZwickRoell’s testXpert II testing software.
This test fixture can also be used for pull-off tests on plaster (band-aid) strips.
DIN EN 1939 describes how the adhesive force of adhesive tapes is determined. To measure the adhesive force of wound dressings or other self-adhesive medical products, the specimen is pulled off a metal plate during the test. This can be performed at various angles.
However, the forces measured in this way are twenty times greater than those arising when the dressing is used on skin. Manufacturers of adhesive products therefore test adhesive force on natural skin, in order also to be able to detect any sensation of pain by the patient, together with any skin irritation, which may occur depending on the adhesive component used.
Another application pertaining to medical textiles concerns the infection prevention in both out-patient and in-patient procedures. Reusable or single-use textiles for surgical masks and gowns and drapes are intended to ensure infection prevention for doctors and patients.
Manufacturers' guidelines are stipulated in the standard EN 13795 and EN 14863 respectively, and now allow OP textiles to qualify under the same requirements and thereby comply with the provisions of MPG, the German Act on Medical Devices.
New functionalities and materials are used in this area as well that are subject to certifications before market introduction and to quality controls during production. A central component of EN 13795 is the test methods for measuring product characteristics such as the tear strength of OP textiles in dry as well as wet states. During transverse and longitudinal strain tensile testing on individual materials or seams, the stress and strain placed on a textile during application is simulated.
These materials are often used as wound dressings and as a component part of dressing materials, as an alcohol swab for preparing injections, or in physiotherapeutic applications. They are an integral part of patient and instrument drapes in the operating theater and used as a cover for dental tampons.
The tests carried out on this material are as varied as the range of applications of the end products. One important test in this field is the tensile test on strip specimens (EN ISO 29073-3 / ISO 9073-3 / ASTM D5035). The measured value is the maximum tensile force as the average value per direction of removal.
The coefficient of variation for the results is calculated. Other important test methods include absorption capacity (EN ISO 9073-6) and strike-through time for liquids (EN ISO 9073-8). A ZwickRoell zwickiLine or ProLine (Z005) testing machine is typically used for these tests.