Up to the Task
A new, carbon-based material technology ushers in a new era in hand and other personal protective equipment.
MANKIND has been utilizing material technology to protect its hands, feet, and other body parts from the hazards associated with living and working since cavemen first wrapped themselves in skins. Occasionally, advances in the material technology associated with personal protective equipment have even presaged dramatic changes in social and political structure. The shining armor of medieval knights, for example, had a great deal to do with the establishment of the feudal state. Now, a new family of carbon-based, biregional fibers promises major performance advances in the ability of personal protective equipment to withstand extreme conditions.
The material, patented as Carbtex(R) fiber, consists of a proprietary thermoplastic core inside a high density carbonaceous sheath. It offers unparalleled resistance to heat, abrasion, and chemicals in a structure that is at once lightweight, breathable, soft, hypoallergenic, and as comfortable as a fine textile. Gloves and other personal protective equipment made of Carbtex materials represent a major improvement in protective wear, in terms of cut, burn, and hot metal splash protection. Protective sleeves made of the material are being used successfully on a large scale in the auto industry, in a number of protective gear and apparel items by the U.S. Army, and in a new line of gloves.
Carbon-based fibers, alone and in blends, have been used for many years in personal protective equipment and fire blocking applications. The original pioneering work done in the United Kingdom blended high carbon (preox) fibers with other high-performance fire-retardant fibers to create various textile blends that provided good thermal protection. However, preox fibers presented problems with poor abrasion resistance, shedding, and a tendency to degrade significantly during washing.
The new Carbtex technology has none of these disadvantages and even improves upon the earlier materials' strengths. Developed by Frank McCullough, Ph.D., in the mid-1990s and recognized by broad patent protection in the United States and worldwide, the new Carbtex fiber exhibits the novel property of black body behavior, both alone and in blends with other textile fibers. This property provides a barrier to radiant energy shone on it, whether from combustion flames, from electric arc discharges, or from the sun.
Because Carbtex imparts this unique property to the other fibers used in a blend, the result is a material that is inherently and permanently flame resistant. At the same time, the material has the effect of being warm in winter yet cool in summer, and it is totally unaffected by UV light. Unlike preox fibers, Carbtex blends will not fibrillate or "lint," so they can be readily used in many demanding environments.
Biologically inert, the materials are also able to be recycled, making both the material and its manufacturing process entirely "green."
Fibers are available in several diameters to provide a large range for protective equipment, and the manufacturer is able to stiffen the fibers without making them brittle. Physical properties are maintained at high temperatures, and the material exhibits better abrasion and cut resistance than para-aramid fibers.
Another interesting property of the material is that it is inherently anechoic, which means it is characterized by an unusually low degree of reverberation, making it an excellent material for sound-dampening applications. A number of Carbtex fabrics are currently available as wovens, knits, non-wovens, and sliverknits and in a variety of colors. Best yet, the material is very competitively priced, costing less than competing materials.
There is a wide range of potential applications for this material technology. Within the PPE category, the most extensively tested application is a cut-resistant sleeve made of a Carbtex fabric. More than 1 million of these sleeves are protecting workers in GM, Ford, and Chrysler metal fabricating and assembly plants. The fabric exhibits excellent cut and burn resistance and is especially liked by workers because it is comfortable in hot temperatures. According to the director of health and safety at one plant, this is an important benefit because workers tend to roll up their sleeves in hot weather or not wear any protective equipment at all, exposing themselves to the risk of significant injury.
The new materials also promise significant benefits in the area of hand protection. A new line of gloves has been developed for welders and others working in environments such as electrical utilities, petrochemical and oil and gas operations, auto manufacturing and racing, firefighting, and more. The new line blends a Carbtex fiber with a para-aramid and provides good cut protection and outstanding thermal protection in a number of applications, in addition to providing a replacement for traditional leather welding gloves.
In addition to cut resistance at normal temperatures, the gloves maintain their physical properties at higher temperatures. Continuous operating temperature for the material is 280 degrees C. The welding gloves are very flexible and offer greater dexterity than normal welding gloves. Made of a durable, seamless knit, they are comfortable to wear and are both warm in the winter and cool in the summer. They can be readily dry-cleaned or machine washed using regular detergent without degrading the fiber. In tests, the Carbtex material was able to endure 150 cleanings without significant wear or shrinkage, while its nearest competitor could take only 30. In addition, while other PPE materials were able to withstand a maximum of 12,000 abrasive rubs, Carbtex withstood more than 45,000.
A number of glove configurations are available for different applications, including: a 13-cut liner for use under leather welding gloves; a heavyweight stringknit for handling hot parts; a loop-out terry and a loop-in terry, both with continuous, 5-inch flared cuff; a thermal knit for high heat protection; a thermal terry; and a "junkyard dog" style glove. The JYD is one of the more popular styles; the new version will incorporate a full leather palm reinforced with a Carbtex shell.
In a number of independent tests, the gloves outperformed para-aramids and heavy leather in electric arc tests (40-100 cal/cm2) and have demonstrated good electrical resistivity from 106 to 1010 cm. In both cut and flash fire tests, the Carbtex gloves outperformed para-aramid and meta-aramid gloves.
Competing products were able to withstand less than 10 seconds of direct exposure to a 1,287 degree C flame, while Carbtex withstood more than 20 seconds. After a three-second flash flame test at 1,593 degrees C, a special mannequin dressed in Carbtex-made coveralls suffered only 9 percent burns while other products yielded as much as 50 percent burns.
It is still early in the development cycle for these new materials, but results demonstrated in applications realized to date show every indication they can provide a safer, more comfortable, and more cost-effective way to handle a multitude of work environment tasks, even under extreme conditions.
This article originally appeared in the September 2004 issue of Occupational Health & Safety.