EN455-2, ISO 11193, ASTM D6319 Tensile Testing of Medical Gloves

medical glove testing 

ASTM D6319ISO 11193, and EN 455-2 are standards used by the biomedical industry to regulate the tensile properties of medical gloves. Used primarily during the quality control process, these tests ensure that the glove material meets expected criteria for tensile strength and elongation so that the gloves do not fail during use. This is extremely important, as glove failure in medical settings could expose the care provider or patient to dangerous and potentially life-threatening contaminants.

Medical gloves are manufactured from a wide variety of materials and are designed for different applications. Materials used for medical gloves generally vary from latex to nitrile, PVC, natural rubber, or polychloroprene, with the requirements for surgical gloves being more stringent than those designed for patient examination. Though there are three standards commonly used to evaluate their tensile properties, their differences are minor, and all require the same basic test setup and procedure. This guide will provide a general overview of the testing process, but should not be considered a substitute for reading the full published standards.

Materials Testing System

Despite the importance of medical glove testing, the procedure itself is fairly straightforward. Most testing to ASTM D6319, ISO 11193, and EN 455-2 can be easily performed on a single column universal testing machine such as Instron's 34SC-5, though labs looking to use their test system for a wider variety of applications may prefer a high-tier 6800 Series test frame in order to take advantage of its additional features. Because medical gloves are made of high-elongation elastomers, an extra height test frame may be required. Due to the low forces involved, a 500 N load cell is considered the maximum when testing to these standards. 




Glove Test Setup
1) Load Cell
A 500N load cell is an appropriate capacity for all glove materials.
2) Pneumatic Grips
Air pressurized grips ensure consistent clamping forces Jaw faces are easily interchangeable to ensure the correct surface texture is used for the material. Elastomeric materials like rubber gloves typically require rubber coated faces due to how thin the specimen is. The rubber coating is able to prevent slippage of the material without damaging the specimen.
3) Bluehill Software
The biomedical method suite includes preconfigured methods for EN455-2 
4) Elastomeric Roller Grips
Roller grips provide a cost effective gripping solution for thin elastomers The roller grip utilizes a proportional clamping pressure which increases as more force is applied to the specimen
5) AVE 2.0
An optical non-contacting strain device can be used to ensure more accurate strain measurement
6) Specimen Preparation
All the major ASTM/ISO/EN standards require a dumbbell shaped specimen to be stamped from the palm of the glove EN 455-2 takes into consideration the potential discrepancies in thickness between the palm and the fingertips. The standard compares their thickness and uses a correction factor for the tensile strength of the speicmen.

 

surgical mask testing
Grips and Accessories

Because medical glove samples are extremely thin and fragile, special consideration must be taken to reduce the likelihood of jaw breaks, where the specimen fails adjacent to - and because of - the grips. This best way to hold these specimens securely is with a set of pneumatic side-action grips and smooth rubber jaw faces. If measuring strain, a non-contacting device is required, as the knife edges on contacting extensometers will be too damaging to the specimens. Instron's SVE2 is a cost effective option for this application.  

2712-045 grips
5 kN Model | 2712-045
2613-002
5 kN Model | 2713-002
Specimen Preparation

Though ASTM D6319, ISO 11193, and EN 455-2 are very similar, EN455-2 is the most popular standard for testing the physical properties of medical gloves because of its specimen preparation requirements. Though all three standards prescribe dumbbell-shaped specimens cut from the glove, EN 455-2 acknowledges that due to the manufacturing process the material can be thinner at the fingertips than it is in the center of the glove. In order to compensate for this, EN 455-2 requires a correction factor if the ratio of the fingertip thickness to the dumbbell thickness is less than 0.9. This ensures that the specimen yields a realistic strength value when tested. All standards require two types of specimens - directly off the manufacturing line, and after undergoing accelerated aging. 

Differences Between the Standards

ASTM D6319 and ISO 11193 are semi-equivalent standards that require different minimum strength and elongation properties depending on the glove material. ISO 11193 is a single multi-part standard which requires the tensile test to be performed in accordance with ISO 37 using the type 2 dumbbell. There are 4 separate ASTM standards which each specify a different glove material. The tensile test is performed in accordance with ASTM D412 and requires the use of the type C dumbbell. EN 455-2 does not differentiate between material types but sets the minimum strength based on the application (surgical or examination).

Traceability and FDA Compliance

Records management is a non-negotiable and stressful part of medical device manufacturing. The Traceability Module available in Bluehill Universal helps users achieve regulatory compliance with FDA 21 CFR Part 11, Nadcap, A2LA, and ISO 17025. 

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