Questions about gloves link to work safety

The proper hand protection plays a tremendous role in keeping plant workers safe. This article answers questions often posed by workers and managers about hand protection products, their applications and limitations.

By Nelson Schlatter, Ansell

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The proper hand protection plays a tremendous role in keeping plant workers safe.  Below are questions often posed by workers and managers about hand protection products, their applications and limitations.

We have applications that involve handling small, hot parts.  Workers need heat protection, yet they require dexterity.  What type of glove do you recommend?

Unfortunately, these requirements are in direct conflict.  The best insulator is air that is not moving.  Materials used for thermal insulation—from wool in clothing to fiberglass in the walls of a house—typically are just different ways of trapping air in small pockets so it cannot move.

To protect workers from contact with hot parts, gloves must contain a thick layer of small air pockets.  But for dexterity, gloves must be thin, which is a direct conflict. 

The gloves selected for this type of application should, therefore, represent a compromise by providing heat protection and dexterity.  Gloves are available that are made with DuPont® Thermastat® yarn, which has individual fibers that contain tiny air pockets.  Gloves made with this type of yarn can insulate and still provide some dexterity.

If parts handled are very hot, a KEVLAR® aramid layer may be needed to resist thermal degradation.  Because cotton and wool are effective in trapping air in small pockets and wicking sweat away form the skin, cotton or wool may be preferable for the inner layers.

Some glove manufacturers do not specify temperature ranges for their insulated gloves.  Why is this?

Because applications vary so greatly, it is difficult to designate one particular temperature as the maximum or minimum for hand protection.  Many factors must be considered, such as whether the source of heat or cold is a liquid, solid or gas.  If a solid, is the material that will be handled made of a thermally insulating plastic that will minimize heat transfer to the glove?  Or, is the material a thermally conducting metal that will maximize the heat transfer?  Is the material heavy, and how long will it be held?  Will the worker repeat the actions that require him or her to wear an insulated glove?

Many glove manufacturers specify useful temperature limits for gloves based on the materials used to manufacture the products (See Table 1).  While a glove’s applicable temperature range will be restricted by these limits, its true useful temperature range will depend on use factors such as those mentioned above.  Other parameters include compressibility of the insulation, coating thickness and type of liner, and coating formulation.  PVC, for example, can vary widely in its thermal properties, depending on how it is formulated.  The ultimate suitability of any insulated gloves must be determined by the end users after proper testing.

 

Appropriate Useful Temperature Limits for Various Polymers

Approximate Low Temperature Limit (ºF)

Polymer Continuous Exposure Intermittent Exposure Short-term Exposure
Cotton

-50

-75

-100

Kevlar®

-20

-40

-60

Natural Rubber

-10

-25

-50

Neoprene

-10

-25

-40

Nitrile

-20

-20

-40

Nylon

-20

-40

-60

Polyester

-20

-40

-60

PVC

0

-10

-50

Approximate High Temperature Limit (°F)

Polymer Continuous Exposure Intermittent Exposure Short-term Exposure
Cotton

200

300

400

Kevlar®

300

600

900

Natural Rubber

170

300

350

Neoprene

200

300

400

Nitrile

250

300

400

Nylon

150

175

200

Polyester

150

175

200

PVC

150

175

200

I am seeking an industry standard for cut resistant gloves—something I can use to compare brands and styles.  Does this type of standard exist?

Yes, ASTM F 1790 is the preferred test method.  Most data at this point has been obtained following F 1790-97, which involves moving a standard blade across a glove material at a standard speed to determine how much weight must be placed on the blade to make it cut through the material with a one-inch stroke.  The new edition of the ASTM standard, F 1790-04, changed to a 20 mm. stroke to conform to the ISO international standard. 

To interpret the data, it is helpful to have a copy of ANSI-ISEA 105-2005, which classifies glove cut resistance on a scale of 0 to 5 based on data from ASTM F 1790-97.  This document also includes classification scales for other properties such as puncture and flame resistance.

Workers within our facility often have to handle lubricated objects that have a slippery surface, which makes them hard to grasp.  Are gloves available that can help workers maintain a more secure grip?

Gloves are offered that include a textured finish on the fingertips, which is ideal for grasping smaller and lighter objects such as test tubes and glassware.  For larger, heavier objects, gloves are available that utilize a unique new technology that creates a roughened surface comprised of microscopic channels in a patented ultra-thin coating that directs fluids away from the grip surface.  These gloves have a relatively dry contact area that allows workers to maintain almost the same grip in oily applications as they would have in dry conditions.      

What gloves do you recommend for handling lacquer thinner?

Lacquer thinner, which is a popular cleaning agent in many manufacturing facilities, typically contains several key ingredients, as listed below.  Although additional ingredients may be present, they will likely fall into these categories:

  • A ketone such as acetone or MEK, which will degrade nitrile, PVC and Viton®;
  • An alcohol such as methanol or isopropanol, which will degrade PVA;
  • An aromatic solvent such as toluene or xylene, which will degrade neoprene, PVC, natural rubber and butyl.

Lacquer thinner may require the most highly protective chemical barrier available since the ingredients in this common solvent mixture work together synergistically to degrade the materials in most gloves offered today.  Laminated film gloves are available that do not degrade in typical lacquer thinners; some of these gloves have breakthrough times greater than two hours.

Although laminated film gloves provide superior chemical resistance, they are very thin and may experience cuts or punctures.  They also lack a textured surface for gripping.  Depending upon the application, the best solution may be to wear a pair of laminated film gloves as a liner under another style of glove that provides the cut protection and grip required.  Fabric-lined neoprene and nitrile gloves and heavy-duty unlined nitrile gloves may be suitable.  Disposable thin nitrile gloves may be used if splashes are occasional and random.

Nitrile gloves without liners may provide adequate protection if the ketone content of the lacquer thinner is relatively low or if the extent of exposure is minimal.

How can I determine what size gloves my workers need?
 
Since proper fit is essential to comfort and dexterity, we recommend measuring each worker’s hand.  You may use a dressmaker’s cloth tape to measure around the hand, above the thumb and below the fingers.  Or, you may wrap a strip of paper around the hand, mark the length, and then flatten the paper and use an ordinary ruler to determine the length.  The diameter of the hand (rounded to the nearest half-inch) is numerically equal to the worker’s nominal glove size. 

This type of measurement, however, does not account for all possible variations in hand size.  For example, some people have long, slim fingers and others have short, stubby fingers.  Because hands differ so much in shape, the most comfortable gloves for an individual worker may be one-half or even one full size larger or smaller than the measured hand size. 

In the past, many glove manufacturers marked their gloves with letter sizes, such as Extra Small (XS), Small (S), Large (L), etc.  These designations had little consistency among manufacturers and sometimes varied from one product line to another.  As a result, many global glove manufacturers now use numeric sizes for most of their products (e.g. 7, 7.5, 8, 8.5, 9, 9.5, etc.). 

How can I determine the shelf life of a specific glove?

Two factors will affect the functional storage life of a glove: the type of material the glove is made from and the conditions under which it is stored.  To maximize their useful life, all gloves should be stored in a cool environment, shielded form ozone and ultraviolet (UV) light.  The latter is especially important for natural rubber gloves, which are extremely susceptible to degradation from UV light—and even the weak UV from fluorescent lights.

Some manufacturers specify a five-year shelf life for industrial-type gloves made of cotton and synthetic materials, with a three-year storage life for natural rubber gloves.  In most cases, these are conservative values—especially for synthetic products designed for multiple uses.

Gloves that have deteriorated during storage will have apparent signs of deterioration.  They will tear easily when stressed and will develop a hard surface layer that will crack when stretched.  The inside of a powder-free glove without a separate donning layer may change from tough polymer to a layer of “goo.”  If gloves, however, look normal, stretch without surface cracks and can be pulled onto the hand without breaking or tearing, they will probably provide the level of protection they were designed to provide.

For more information about PPE for industrial applications, visit www.ansellpro.com or call 800.800.0444.

 

Thermastat® and KEVLAR® are registered trademarks of E.I. de Pont de Nemours and Company.

Viton is a registered trademark of DuPont

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