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Environmental, Health & Safety :: Plant & Personnel Safety :: Protective equipment

July 15, 2008

Finding the Right Gloves To Fit the Application

There is a wide range of gloves available for hand protection on the job. Matching gloves to their chemical-resistance properties is one criterion for selection

Nelson Schlatter Ansell

Workers in the chemical process industries (CPI) would certainly benefit from the "perfect" glove that would be thick enough for thermal insulation, thin enough to promote dexterity and tough enough to protect workers from cuts and abrasion. The glove would also protect against all known chemicals and be offered at a minimal price. This perfect glove, however, does not exist. Processors and handlers, therefore, must provide workers with the most suitable, available gloves for the application, considering individual circumstances and how the gloves will be used. Considerations to help choose proper gloves for a given application, with particular focus on chemical resistance, are presented here.

Factors to Consider

A person who selects gloves needs to know much more than just the name of the chemical to be handled. If an employee, for example, is working with nitric acid, then PVC (polyvinyl chloride) and neoprene are the preferred glove materials. Several questions, however, must still be answered. Is the worker cleaning up spills? If so, the person will require highly chemical-resistant gloves with good storage stability because the gloves may be kept in a spill-control cabinet for several years until they are urgently needed.

Is the person handling sealed bottles, which will require minimal protection unless the bottle breaks? Could a spill be caused by breaking a bottle? If so, the worker will need protection from cuts as well as nitric acid. What is the probable length of exposure? The longer workers are exposed to a certain chemical, the greater the level of protection required.

The chemical concentration must also be considered. Is the compound present only as a trace impurity? Is the employee working with a pure chemical or a dilute solution? If the chemical is diluted, what solvent was used for dilution?

Companies sometimes over-specify gloves, which can lead to unecessary expense. Once for example, a request from a chemical company indicated the need for gloves that would resist "high concentrations" of toluene. When questioned about the application, it was revealed that workers would be exposed to groundwater with a toluene concentration of less than 100 parts per million. While this is indeed a high concentration for toluene in groundwater, in this case, gloves that protect against water would be more appropriate and cost-effective than gloves that protect against pure toluene.

Glove Types

Gloves are generally categorized according to the materials used and whether they are supported or unsupported (see definitions below). The following glove types are available in a range of lengths, thicknesses and finishes, while some styles are offered with special modifications.

Unsupported vs. supported

Unsupported gloves are made of materials such as natural or synthetic latex, nitrile and neoprene and achieve their glove shape by dipping hand forms directly into the glove compound without a supporting liner or fabric. This type of glove generally provides the dexterity and tactile sensitivity required for many chemical applications.

CHEMICAL-RESISTANCE INFORMATION FOR VARIOUS GLOVE MATERIALS

Chemical Laminate Nitrile Neoprene Polyvinyl Polyvinyl Natural Butyl Viton
        Alcohol Chloride Latex    
        PVA PVC      
NR=not recommended; P=poor; F=fair; G=good; E=excellent; >480 indicates breakthrough times that are greater than 480 minutes (8 h) and correlates well with extremely good degradation resistance Permeation is also color coded: red indicates breakthrough times of only a few minutes; yellow indicates breakthrough times of up to two hours; and blue indicates longer breakthrough times
Acetone >480 NR E P NR E >480 P
Ammonium hydroxide E >480 E NR E E >480 >480
Butyl glycol ether >480 E E E P E >480 >480
Ethyl acetate >480 NR F G NR G E NR
Ethylene glycol >480 E E F E E >480 >480
Gasoline (hi-test) E E NR G P NR F >480
Hydrochloric acid, concentrated >480 E >480 NR E E >480 >480
Hydrofluoric acid, 48% >480 E >480 NR G E >480 180
Methanol >480 E E NR G E >480 F
Methylene chloride E NR NR G NR NR G E
N-Methyl-2-Pyrrolidone >480 NR NR NR NR E >480 NR
Mineral spirits, rule 66 >480 E E E F NR 60 >480
Perchloroethylene >480 E NR E NR NR P E
Sulfuric acid, concentrated >480 NR F NR G NR >480 >480
Xylene >480 G NR E NR NR P E

Unsupported gloves offer a broad spectrum of chemical resistance, based on the material used. Nitrile gloves, for instance, are excellent for many chemical processing, oil refining, food processing and petrochemical applications. Gloves made with a neoprene and natural-rubber-latex blend provide the protection workers need in food processing facilities and certain chemical- and pesticide-manufacturing plants.

Supported gloves are made by dipping a hand form wearing a knitted- or woven-cloth liner into a glove compound such as nitrile. The liner supports the compound and adds strength to the glove. Some supported styles have continuous coatings to ensure protection from chemicals. Cotton and polyester may be used in various combinations as a yarn for woven or knitted products, coated with various compounds — including natural latex, neoprene and PVC — to protect against petrochemicals, oils, acids, alcohols and solvents.

Supported gloves with non-continuous coatings are better suited for applications that require comfort and grip. Many supported gloves also offer cut, snag, puncture and abrasion resistance.

Fabric gloves

This category includes general purpose gloves made with polyester, nylon and cotton; cut-resistant gloves constructed with Kevlar, Dyneema and steel; stretch gloves made with small percentages of natural latex and Lycra yarns added to other fibers; and special purpose gloves with materials, such as thermal foam or vibration foam. Special purpose gloves include extra clean gloves and sterile gloves.

General purpose gloves. Nylon, polyester and cotton gloves are comfortable and protect against snags, punctures, cuts and abrasion. They do not, however, protect against chemicals and liquids, which is why chemically resistant gloves may need to be worn as liners in some applications. Nylon is an alternative fabric that may be used in cleanrooms, automotive paint rooms and inspection stations where there is concern about lint contamination.

Cut resistant gloves. Gloves made with Kevlar typically provide the best cut protection based on price, and gloves made with Spectra or Dyneema ultra-high-molecular-weight polyethylene typically offer the best cut protection based on weight. Steel assures the best cut protection based on bulk. None of these materials, however, will protect the hands from liquids. Liquid-protective cut-resistant gloves need to be coated with a compound, such as nitrile.

Stretch gloves. Most of today’s fabric gloves are made from knitted fabric rather than woven fabric, because knits have a natural tendency to stretch and fit closely. Natural rubber latex is used to make the least expensive additive elastic yarn for making tighter-fitting gloves and cuffs. Workers, who need a tighter fit and know or suspect they have a latex allergy, should consider switching to gloves made with a synthetic alternative, such as spandex.

Special purpose gloves

Specialty gloves include those made with thermal foam for protection from heat or cold, vibration-absorbing foam for workers handling power tools and other vibrating machinery, or products with radiation-absorbing additives such as lead or bismuth. This category also includes extra-clean gloves for electronics cleanrooms and sterile gloves for pharmaceutical facilities.

Chemical Barriers

Descriptions of glove materials that may be used with various chemicals follow, with advantages and disadvantages listed. In addition, the Table above summarizes some chemical-resistance information. Gloves are listed below in order, by degree of specialized use.

Natural rubber (latex)

Natural-rubber latex gloves (Figure 2) are generally unsupported and available in many styles, including cleanroom and sterile styles. These gloves provide excellent protection from bases, alcohols, and dilute water solutions of many chemicals, with fair protection against aldehydes and ketones.

Advantages: Low in cost, good physical properties, good cut protection in heavy duty styles 1 , excellent dexterity

Disadvantages: Poor protection against oils, greases and organic compounds; risk of protein allergies. Some manufacturers use shortcuts that result in a poor quality product

1. Products that provide "cut resistance" and "cut protection" do not completely prevent or eliminate the potential for cuts or punctures, and are not intended or tested to provide protection against powered blades or other sharp or rotating equipment. Users are encouraged to always use caution and care when handling sharp materials.

Polyvinyl chloride (PVC)

Gloves made with PVC are generally available in heavy supported or lightweight disposable styles, and protect against strong acids, strong bases, salt solutions and some heavy organic chemicals. Many PVC or vinyl gloves offer good abrasion and cut resistance, although some styles may be susceptible to cuts.

Advantages: Low in cost, fair physical properties, minimal risk of allergic reactions

Disadvantages: Organic solvents can wash plasticizers out, leaving "holes" in the glove polymer on the molecular level that may allow rapid chemical permeation; gloves from some manufacturers are poor quality

Nitrile (Buna, NBR)

Nitrile gloves (Figure 1) are generally available as disposable, medium-weight unsupported, or lightweight supported styles. They protect against oils and greases (including animal fats), xylene, perchloroethylene and aliphatic solvents. They also protect against most agricultural pesticide formulations, chemicals and biological components used in weapons, and other chemicals.

Advantages: Low in cost, excellent physical properties, good dexterity; excellent resistance to snags, punctures, abrasions and cuts

Disadvantages: Poor protection against many ketones, some aromatic chemicals, and medium-polar compounds

Neoprene

Neoprene is available in disposable, medium-weight unsupported, medium-weight supported and heavy supported styles. Neoprene protects against a broad range of oils, oxidizing acids (nitric and sulfuric), polar aromatics (phenol and aniline), glycol ethers, oils, greases and many other chemicals. Other types of gloves may, however, offer better protection against some of these chemicals.

Advantages: Medium cost, medium physical properties, medium but broad-ranging chemical resistance

Disadvantages: Less resistant to snags, punctures, abrasions and cuts than nitrile or natural rubber

Butyl rubber

Butyl rubber is used only in medium-weight unsupported gloves (Figure 3).

Advantages: Dexterity and outstanding resistance to moderately polar organic compounds, such as aniline and phenol, glycol ethers, ketones and aldehydes

Disadvantages: Poor protection against non-polar solvents, including hydrocarbons, chloro- and fluoro-carbons; expensive

Polyvinyl alcohol (PVA)

PVA is used for medium-weight supported gloves that provide a high level of resistance to many organic chemicals, such as aliphatics, aromatics, chlorinated solvents, fluorocarbons and most ketones (except acetone), esters and ethers.

Advantages: Very rugged and highly chemical-resistant; good physical properties with resistance to snags, punctures, abrasions and cuts

Disadvantages: Will quickly break down when exposed to water and light alcohols, less flexible than many other types of chemically resistant gloves, expensive

Viton

This compound is used primarily in medium-weight unsupported gloves to protect against aromatics, chlorinated solvents, aliphatics and alcohols.

Advantages: Good dexterity, outstanding resistance to many organic compounds

Disadvantages: Poor resistance to certain solvents, including ketones, esters and amines; poor physical properties, extremely expensive

Sealed-film (laminate) gloves

Laminate is one of the most chemically resistant materials available and protects against almost anything, including most chemicals and biological compounds used in weapons. Gloves made with this material are excellent for hazmat applications. Laminate gloves are often used as liners, which takes advantage of their thinness and is often the best way to address their disadvantages.

Advantages: Moderate cost; thin; outstanding resistance to almost all organic compounds

Disadvantages: No grip finish, poor physical properties (very low resistance to physical damage), not as form-fitting as dipped gloves

Chemical Resistance Tests

Chemical-resistant gloves are typically tested for degradation, permeation-breakthrough times, and final permeation rates.

Degradation is a deleterious change in the physical properties of a glove due to the effects of a chemical. It is commonly evaluated by measuring weight or dimension changes upon exposure. Currently, no widely used standard degradation test exists for gloves, although several groups have tried to converge on one. The problem is that during actual use, only the outside of a glove is exposed to chemicals, and it is difficult to test the outside of a multi-layer glove without having the results distorted by the properties of the inner layers.

Permeation is the process by which a chemical moves into and through a chemically resistant glove film by adsorption on the outside, diffusion through, and then desorption on the inside. Measurements commonly tabulated include breakthrough time (how long after exposure the permeation "valve" was opened) and permeation rate (how wide it was opened).

Both degradation and permeation result from a chemical being absorbed and diffused into the film. The amount of chemical absorbed and the rate of transport, however, are independent variables, which means that neither property can be predicted based on the test results for the other property. A simple degradation test, therefore, cannot be used to extrapolate the results expected from a more complex and time-consuming permeation test.

ASTM F 739

This is the permeation test most commonly used and represents the original permeation standard, although a substantial amount of data has been accumulated since it was first issued. European-standards writers adopted ASTM F 739 with minor modifications as EN 388. During testing, permeation test cells are filled once and remain filled. The results typically provide the time delay until the chemical breaks through, and the flowrate through the material, which increases to a final constant value.

Method F 739 does not realistically simulate most end uses for chemically resistant gloves. During actual use, gloves are likely to be warmed by the wearer’s hands to higher temperatures than those used in testing, which will make chemicals permeate more rapidly. Gloves will be flexed and squeezed rather than held in place in a test cell, which will also make chemicals permeate more rapidly.

Gloves, however, are typically worn to protect against possible splashes — not continuous liquid contact. Chemicals, therefore, will permeate through more slowly during actual use than in a standard permeation test. Breakthrough times and permeation rates from F 739, therefore, should not be considered as absolute constants. The data is useful only to compare gloves and obtain a general indication of how well they can be expected to perform.

ASTM F 739-07

This is the newest version of ASTM F 739 and uses 27°C as the standard temperature since gloves are generally warmer than room temperature during use. Much older data and European data were obtained at room temperature (21°C). Europeans decided that a consistent established method is more important than a somewhat more realistic method, which is why they continue to use 21°C as the test temperature. When selecting gloves, it is important to compare test data that were obtained at the same temperature.

ASTM F 1383

This test can be used to simulate intermittent contact applications, although the test focuses on permeation only. During F 1383 tests, permeation test cells are filled and emptied repeatedly on a schedule developed to match the intended end use. Air or nitrogen is blown through the chemical compartment during the entire "empty" cycle, with evaporation away from and diffusion into the sample occurring simultaneously. The ASTM F1383 Intermittent-Contact Permeation Test, therefore, may provide a more realistic permeation measurement of real-world breakthrough times.

Breakthrough ratings indicate how long a glove may be safely worn after a splash occurs. Final permeation rates show how much of a chemical permeates the glove barrier during continuous exposure. While lower ratings are better, there is still no allowable skin contact threshold limit value (TLV) for any chemical. Most people who select gloves tend to pay more attention to the breakthrough time.

Conclusions

Since the "perfect" glove does not exist to protect workers in every chemical application, gloves should be selected that provide the appropriate level of protection for the specific chemical handled. Questions should be considered regarding the chemical concentration and length of exposure, dexterity, tactile sensitivity and cut protection required.

Many glove manufacturers offer hand protection products that protect workers from a variety of chemicals. In general, natural rubber latex is the least expensive alternative for tight-fitting gloves that resist bases, acids, alcohols and the diluted aqueous solutions of most chemicals. Unsupported gloves offer a broad spectrum of chemical resistance, depending on the material used. Supported styles are often used for general purpose, chemical- or cut-resistant requirements.

Edited by Dorothy Lozowski

Notes

  1. Kevlar is a registered trademark of Dupont. Dyneema is a registered trademark of Royal DSM, N.V. Lycra is a registered trademark of Invista.

  2. Neither this article nor any other statement made herein by or on behalf of Ansell should be construed as a warranty of merchantability or that any Ansell product is fit for a particular purpose. Ansell assumes no responsibility for the suitability or adequacy of an end user’s selection of gloves or clothing for a specific indication. Upon request, Ansell will provide a sample of material to aid you in making your own selection to meet your own individual safety requirements.

Author

Nelson Schlatter is a technical applications chemist for Ansell Occupational Healthcare (1300 Walnut St., Coshocton, OH 43812; Phone: 740-623-3591; Email: nschlatter@ansell.com; Fax: 740-623-3556). He has worked with Ansell for 30 years on the chemical interaction and processing of textiles, rubber and solvents. He presently answers technical inquiries and provides recommendations regarding the proper use of Ansell gloves and clothing. Schlatter holds a B.S. degree from the University of Delaware. He is an active member of ASTM Committee F-23 on Protective Clothing and belongs to International Safety Equipment Organization Committees on hand protection and clothing.
 

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