The Complete Guide to
Understanding and Selecting
Coated Work Gloves for Hand Protection
NIGDA
National Industrial Glove Distributors Association
This guide contains information designed to assist industry professionals in meeting their needs for hand protection using coated gloves. This guide does not constitute expert safety advice, however, users are advised to work with a competent safety professional in determining their own glove or safety programs.
In addition, the information referenced herein could be subject to change in the future. The National Industrial Glove Distributors Association does not guarantee the accuracy of the safety language in this manual. NIGDA will provide updates to this guide as appropriate.
Copyright 1997 by NIGDA. All Rights Reserved. No part of this book may be reproduced, stored in a retrieval system, or transcribed, in any form or by any means, electronic, mechanical, photocopying or otherwise without the written permission of NIGDA.
Acknowledgments
The Complete Guide to Understanding and Selecting Coated Work Gloves for Hand Protection was made possible due to the expertise and research of several key NIGDA members. NIGDA would like to thank you for your efforts and contribution in producing this comprehensive industry tool:
The original author of the Guide, Jeffrey O. Stull, International Personnel Protection, Inc., with contributions from the following:
Craig Wagner, Best Manufacturing Company
Alice Williams, MAPA Pioneer
Bill Dutton, The Montgomery Group
Jim McFadden, The Montgomery Group
Norman Rivkin, Saf-T-Gard International
Neil Tillotson, Tillotson Corporation
Table of Contents
Introduction...... 1
History of Coated Work Gloves...... 2
Early development and uses
Key industry developments
Recent industry growth
Manufacturing Methods...... 5
Dipping fabric gloves
Assembly from coated fabrics
Coated Work Glove Features...... 10
Liners or fabric substrates
Coating materials
Cuff designs
Grip design
Glove sizing
Performance Properties...... 20
Overall integrity
Water repellence, water resistance or water-proofness
Chemical resistance
Biopenetration resistance
Physical hazard resistance
Heat and flame resistance
Resistance to cold temperatures
Electrostatic resistance, linting, and extractable matter
Durability
Weathering resistance
Human factors
Guidelines for Coated Work Glove Selection...... 38
Future Considerations...... 42
Industry needs and new product development
Manufacturing environmental concerns
Continued development of industry standards
Glossary...... 44
Introduction
In industry, workers often require protection against a variety of workplace hazards. These may include physical, chemical, biological, or thermal hazards. To provide hand protection, gloves must provide appropriate protection to the wearer while allowing the worker to adequately function to perform work tasks. Depending on the type of protection needed and the application of use, there are several kinds of gloves which can be selected. These gloves can be made of leather, various woven or knit textiles, rubber, plastic, nitrile, neoprene, metal, and various combinations of these materials. One combination of materials involves the use of rubber, pvc, nitrile or neoprene coated on fabric substrate, known as coated work gloves or supported gloves.
This guide is specific to one class of gloves for worker protection -- Coated work gloves. While there are some test method standards, there are no comprehensive standards on glove performance in the United States, which establish minimum performance for coated work gloves. Therefore end users and specifiers must have a thorough understanding of glove characteristics and performance properties in order to select appropriate gloves. This guide is intended to provide information necessary to make glove selection decisions.
History of Coated Work Gloves
Early Development and Uses
The coated work glove industry grew out of the leather and cotton glove manufacturing business in the early 1930s. At that time, several industries needed long wearing, liquidproof gloves to better protect employees. The best promise for providing this performance involved using natural rubber as a coating for cotton gloves. What made the coating with natural rubber possible was raising the rubber solids content in latex (water-based) solutions for dipping fabric gloves. Two companies are credited with developing the first rubber coated cotton gloves at about the same time—Tillotson Glove Company and Edmont Manufacturing (which later became Best Manufacturing Company and Ansell-Edmont Industrial). Both companies succeeded in producing natural rubber glove coated gloves by dipping wooden glove forms into tanks of liquified natural rubber.
Early on, the process of fabricating coated gloves was difficult, labor-intensive, and beset with many problems. Sometimes, rubber would leak through the cotton liner and subsequently dry and harden inside the glove sometimes ruining the glove forms. In other cases, non-uniform heating of the gloves during the curing process would cause the rubber to separate at the crotch of the fingers, causing "leakers." At times, the rubber formulation was not consistently uniform, and lumps of hard rubber would stay in the bottoms of the drums, raising the cost of the basic usable material.
Initially, rubber coated gloves were sold locally to platers, fish merchants, cement and brick workers, meat packers, and other industrial users. With time, the need for rubber coated work gloves expanded to new applications throughout the country. By the mid to late 1930s, other companies entered the coated glove manufacturing industry including Hood Rubber, Latex Glove Manufacturing, U.S. Rubber, and Wells-Lamont.
Key Industry Developments
Several key developments allowed the coated work glove industry to expand and pursue new material technologies.
For natural rubber coated gloves, increases in the amount of dissolved rubber solids and breakthroughs in dipping technology by International Latex Corporation (later becoming Playtex Company) and other companies led to easier glove production and more consistent glove performance. During the 1940's, World War II left the world supply of natural rubber inaccessible to many U.S. manufacturers. Limited supplies of natural rubber provided incentives for synthetic rubber development. It also established certain companies with responsibilities for manufacturing coated gloves based on government directives.
The introduction of synthetic rubber and alternative materials provided for the diversification of the coated work glove industry. Chloroprene was first developed in the early 1930's under the trade name Neoprene® by E. I. du Pont de Nemours & Company as an oil-resisting rubber. It was first commercialized for coating gloves in 1942. At about the same time, polyvinyl chloride as a coating material for gloves became a popular alternative to chloroprene and natural rubber.
Although nitrile rubber was developed by both the United States and Germany in the 1930's, it was not until the early 1960's when it became practical to coat gloves with nitrile rubber. This is because nitrile rubber tended to crack and split. New formulations were developed in the 1960's to better control the quality of the rubber and overcome these problems.
The key element in the development of new formulations of nitrile gloves in the 1960’s was nitrile latex from Standard Brands who was bought by Reichhold (Tylac) in 1977. Nitrile gloves made prior to that generally used solvent-based dipping of solid nitrile rubber dissolved in a cement solution.
Paralleling the use of new coatings was the identification of new fabrics. Up until the 1960's, most cotton and other linings were made of non-stretch fabrics using multiple piece patterns. The introduction of knits and stretch fabrics such as cotton jerseys allowed 2-piece patterns, reducing labor costs and providing more comfortable wearing gloves.
Attention on glove performance was primarily driven by the U.S. Occupational Health & Safety Administration with new requirements for protecting workers from various workplace hazards during the 1970's. Later that same decade, the American Society for Testing and Materials (ASTM) established a committee on protective clothing. This committee seeing the need to better define protective clothing performance, established standard test methods for measuring the chemical resistance and other glove performance properties. These regulations and standards led to increased awareness of glove performance and concerns for selecting appropriate gloves.
Recent Industry Growth
Much of the coated work glove industry growth came during the 1950s, 1960s, and 1970s as many employers identified the need to provide their employees with protective gloves and other safety equipment. Additional growth was fueled by increased end user awareness of workplace hazards and standards, which allowed product comparison.
Today in the United States, the greatest volumes of coated work gloves sold are still made of pvc, but nitrile rubber now accounts for greater total revenues for coated glove sales. Concerns over allergic reactions to natural rubber has driven some users to synthetic rubber or plastic coated gloves.
The growth of the domestic market has stagnated partly due to increased foreign competition (based on cheap labor) and industry pursuit of "engineering" or "administrative" controls to limit employee contact with hazards. In addition, other products such as unsupported gloves often supplant coated glove use in some applications (unsupported gloves offer better dexterity and tactility, though they provide less physical protection to the wearer).
Coated gloves are principally used in the petrochemical/refining, material and chemical handling, plating, degreasing, and other operations where abrasion, liquidproof or chemically-resistant gloves are needed which are durable and provide a relatively high level of physical protection.
Many of the new uses for coated work gloves come from applications where no protection is currently used. For example, some of the best growth opportunities in the coated work glove are expected in the retail (consumer) market.
Manufacturing Methods
Coated gloves or "supported" gloves differ from "unsupported" gloves by having an inner knitted or woven cloth liner. The lining supports the coating and adds strength. There are two principal manufacturing methods for constructing coated gloves. These include:
•Dipping fabric liners into glove polymer compounds, or
•Assembling the glove from pieces of coated fabrics.
Dipping Fabric Gloves
In the dipping process, molds or formers made of porcelain or metal in the shape of different sized hands are mounted on a rack, covered with knit or woven cloth gloves, and are first dipped into a suspension of the polymeric material, natural latex, synthetic rubber, or plastic polymer. The polymer layer must only penetrate the outer part of the fabric and not through the complete fabric. There are three alternative methods of dipping fabric-lined gloves:
1.Coagulant Dipping - The fabric covered former is first dipped into a coagulant solution and then into the polymer suspension.
2.Straight Dipping - The viscosity of the polymer suspension is increased so that fabric penetration is controlled on immersion. After the first dipping, the thickness of the polymer layer can be built up by additional dipping.
3.Heat Sensitive Dipping - The former is fitted with the liner and then heated to 60C (140-175oF) and then dipped into the polymer suspension. The heating of the former sets up a temperature gradient across the fabric, which allows the polymer to penetrate only the surface before the heat causes the compound to gel.
The depth and orientation of dipping can be used to provide gloves that are partly dipped, such as gloves where only the palms are coated. Photographs of the dipping process are shown in Figures 1-2.
Figure 1. Cloth covered glove handforms being dipping into polymer suspension.
1
The Complete Guide to Understanding and Selecting
Coated Work Gloves for Hand Protection
Figure 2. Second dipping of glove handforms into polymer suspension during straight dipping process.
Different formulations of the polymer are used to create the desired characteristics of the resultant coating. For example, natural rubber latex which contains 36% rubber, 60% water, 1.7 resins, 2% other material (proteins, ash, and sugars) must be preserved with ammonia and additional preservatives. In addition, rubber compounds must use different vulcanizing agents, activators, and accelerators for the vulcanization (curing) process together with anti-degradant agents, stabilizing agents, heat sensitive agents and coagulants.
Gloves produced by dipping are usually dried and vulcanized in an oven with hot air. Vulcanization is the process by which the polymer is hardened. The final operation in glove manufacturing is to remove the product from the former (called stripping) as shown in Figure 3.
Assembly From Coated, Laminated, or Impregnated Fabrics
Coated work gloves can also be made by sewing coated, laminated, or impregnated fabrics into glove forms. This process permits the combination of coated, laminated or impregnated fabrics with other materials such as leather and woven/knit fabrics.
Figure 3. Finished gloves being removed from handforms.
Coated Work Glove Features
Coated glove designs vary in the type of liner, coating material, cuff design, grip design, and length.
Liners or Fabric Substrates
Coated work gloves can be made of knitted cotton or rayon or woven fabrics of cotton, wool, or synthetic blends. In addition to providing the "support" for the coating material, the lining yields most of the glove's physical strength and resistance to puncture, snagging, cutting, abrasion, and tearing. Linings also generally allow easier donning and doffing, provide hand comfort, and may absorb perspiration. Some unsupported gloves contain non-fabric flocking inside the glove, but these treatments are not considered coated-work gloves.
Knit fabrics generally provide better comfort and less seams in glove liner construction. Interlock and jersey are examples of knit fabrics. Interlock knits generally provide more flexibility and launderability while jersey knits provide relatively more cushioning and insulation. Woven fabrics, such as cotton flannel and rayon often require more pieces in the liner glove pattern but may offer relatively more strength.
Cotton linings provide good absorption of perspiration and are generally considered to offer relatively good hand comfort compared to rayon and synthetic fibers.
Nylon mesh materials are used in the back of some gloves to permit significant breathability and comfort to the wearer.
Liner styles of construction include:
1.Two Piece - the glove liner is made from two pieces of material sewn in the general form of a glove.
2.Five Piece - the front of the glove liner is made from one piece, while the back is sewn from a number of parts. This style provides a formed glove and usually has a knit wrist.
Coating Materials
Coating materials include natural rubber or latex, synthetic rubber, and plastics. Common glove coating materials include:
•Natural rubber
•Synthetic rubber
Chloroprene
Nitrile rubber
•Plastics
Polyurethane
Polyvinyl alcohol (PVA)
Polyvinyl chloride (PVC)
Tables 1 and 2 provide a general comparison of coating properties and chemical resistance, respectively.
Natural rubber is found in nature in over 200 plants, but its most common source for gloves is the Hevea Brasiliensis tree. Natural rubber dispersed in water is known as latex. Natural rubber has a very high elasticity compared to other glove materials, excellent cut and tear resistance, and outstanding grip and temperature resistance. While it is flexible and durable over a wide range of temperature -18-149C(0 to 300oF), it has poor flame resistance. In general, natural rubber withstands water, alcohols, and some ketones, but has poor chemical resistance against most hydrocarbon and organic solvents. It is the
most common coating material for supported gloves.
1
The Complete Guide to Understanding and Selecting
Coated Work Gloves for Hand Protection
Table 1. General comparison of different glove coating physical
properties.
Coating Material / AbrasionResist. / Cut
Resist. / Puncture
Resist. / Tear
Resist. / Flexibility / Heat
Resist. / Ozone
Resist. / Relative
Cost
Natural rubber / E / E / E / E / E / F / P / Medium
Butyl rubber / F / G / G / G / G / E / E / High
Chloroprene / E / E / E / G / G / G / E / Medium
Fluorocarbon rubber / G / G / G / G / G / G / E / Very High
Nitrile rubber / E / E / G / G / E / G / F / Medium
Polyurethane / E / G / G / G / E / G / G / High
Polyvinyl alcohol / F / F / F / G / P / G / E / Very High
Polyvinyl chloride / G / P / G / G / F / P / E / Low
Ratings:E - excellent; G - good; F- fair; P - poor
Note: Ratings are subject to variation depending on formulation thickness, and the type of fabric support
Source:Guidelines for the Selection of Chemical Protective Clothing, 3rd Edition, American Conference of Governmental Industrial Hygienists, Cincinnati, Ohio, 1987.
Table 2. General comparison of different glove coating chemical resistance.
Coating Material / Alcohols / Amines / Esters / HalogenCompds. / Hydro-
carbons / Inorganic
acids/bases / Ketones / Nitriles
Natural rubber / * / N / N / N / N / * / N / N
Butyl rubber / R / * / R / N / N / * / * / R
Chloroprene / R / * / N / N / N / * / N / *
Fluorocarbon rubber / R / R / N / R / R / R / N / R
Nitrile rubber / R / * / * / N / * / * / * / N
Polyurethane / N / na / N / N / * / N / N / na
Polyvinyl alcohol / * / * / R / * / * / N / * / R
Polyvinyl chloride / * / N / N / N / N / * / N / N
Ratings:R - recommended; N - not recommended; * - mixed performance; na - data not available
Note: Ratings are subject to variation depending on formulation thickness and provided only as general assessment of coating chemical resistance; Use specific data for the selected glove and chemical combination.
Source:Information consolidated from Guidelines for the Selection of Chemical Protective Clothing, 3rd Edition, American Conference of Governmental Industrial Hygienists, Cincinnati, Ohio, 1987.
1