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Putting Gloves to the Test
Material testing: a manufacturer's strong point
By Lisa Arnseth
Whethera procedure is being performed in the OR or in an exam room, gloves are acrucial part of the job. Evaluating the durability of the glove under a varietyof situations is not something to be done on the floor, but by the manufacturerthrough a variety of research and development applications.
Several manufacturers and industry professionals have developed a set ofstandards to determine the amount of strain a glove can handle before it willcompromise its protection abilities. The American Society for Testing andMaterials (ASTM) has formulated voluntary consensus standards for severalindustries, including the medical materials arena. Manufacturers follow the ASTMprescribed testing methods and classifications. Timothy Brooke is a manager inthe Technical Committee Operations division and a spokesman for the ASTM'sCommittee D11 on Rubber. According to Brooke, the committee is made up frommanufacturing representatives, academia and healthcare workers as well as FDArepresentatives. The FDA is the governing body that oversees whether or notcertain gloves are acceptable to be sold in the US. "We (ASTM) essentiallymanage the process whereby the standards are developed," says Brooke.
Several of the top glove manufacturers refer to ASTM standards when preparinggloves for market release. Richard McManuis a product manager at InstronCorporation, a materials testing equipment provider, based in canton, MAanswered some common questions as to what happens to a glove before it reachesthe healthcare worker.
How has glove testing technology changed over the last decade?
McManuis: Modern glove materials stretch more before failure. Thisrequires testing instruments to have a larger test area and more crossheadtravel if standard specimens are used. More suppliers are using software todayto automate data collection, result calculations and reporting.
More manufacturers are also using a strain measuring instrument called anextensometer in place of having the test operator hold a ruler beside thespecimen to "eyeball" extension during the test. Since the rubber isvery thin, new video extensometers that do not physically contact the specimenare beneficial.
What are the common testing methods used by manufacturers today to testgloves prior to hospital utilization?
McManuis: Mechanical testing is limited to measuring tension andstrain, and then calculating stress at various points. Typical tension testresults are tensile strength, ultimate elongation, and stress at 500% strain.
How are physical factors, such as flexure, friction and tension, tested bymanufacturers?
McManuis: Flex and peel tests are not done on glove materials. Thereis some tear and some coefficient of friction testing done but tension is by farthe most common mechanical test. ASTM D3577 specification for rubber surgicalgloves, ASTM D3578 specification for rubber examination gloves and ASTM D6319specification for nitrile examination gloves for medical application allrecommend ASTM Method D412 for tension testing. Some suppliers have changed fromusing the ASTM D412 die C specimen to the shorter die D specimen to reduce theabsolute crosshead travel required to produce failure. Peel tests are often doneon glove packaging.
How can the aforementioned tests fail?
McManuis: The mechanical tests are a reliable measure of gloveperformance. Correlation between test results and in-use failure isstraightforward.
In regards to quantity of actual gloves tested, do manufacturers tend todo spot-testing?
McManuis: QC testing protocols vary but are usually either spot testsor some fraction of production quantity. The mechanical tests are destructive soit is not possible to do 100% testing. Some testing is for research anddevelopment purposes as well. Gloves are normally tested as they come off theproduction line and after accelerated aging as specified by ASTM Method D573.
How are tests performed differently for different types of gloves?
McManuis: I am not aware of different test methods as a function ofend-use. Most glove materials exhibit 700% to 1000% strain to failure. Pulling aglove onto the hand requires no more than 200 to 300% strain, so there is a goodsafety factor.
Are there any new testing methods on the horizon, especially when it comesto new glove materials now on the market, such as nitrile?
McManuis: There has been a notable increase in latex sensitivityproblems driving suppliers to provide nitrile rubber gloves in addition tonatural rubber. ASTM Specification D6319 for nitrile gloves was adopted justlast year (2000), but it recommends the same tension test method since theend-use has not changed.
As more and more materials come into use, I do not expect to see anysignificant change in the mechanical test methods.
For more information on the ASTM and information on ordering the AnnualBook of ASTM Standards, visit www.astm.org.
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