Detection of defects in protective barriers

Details Detection of defects in protective barriers Detection of defects in protective barriers

1998-07-02

2001-03-20

Metjahic, Safet (Department: 2858)

Electricity: measuring and testing

For insulation fault of noncircuit elements

Reexamination Certificate

active

06204669

ABSTRACT:

BACKGROUND OF THE INVENTION
There is a great concern among world health organizations and regulatory agencies as to the quality of protective products such as condoms, gloves, implantable enclosures (breast implants), protective garments, and medical and food packaging to ensure protection against sexually transmitted diseases and toxic materials. The greatest concern in health care and toxic industrial environments is that these products be free from defects before and during usage. Protective barriers come in a wide variety of geometries, thicknesses and materials of construction depending upon the application. Latex and synthetic polymers are frequently used for barriers such as condoms, gloves, garments and implants. Although packaging may be formed only of polymeric material, it may also include other types of materials to ensure the integrity of the packaging, such as metallic films. Other composite materials may be used in other areas of applications as barrier materials, for example, in a work place involving electrical and/or chemical hazards.
Defects such as holes and tears can occur in a variety of geometries and sizes, from large tears to small pinholes. In health care applications in order to protect health care providers, the acceptable defects are preferably in the micron or sub micron range. The herpes virus is about 0.15 micron, and the AIDS virus, about 0.1 micron. Small biological particles may be charged, producing ionic layers about the particle which hydrodynamically create much larger particles. However, even with a considerably larger particle size, such biological particles will be in the micron range.
In industrial applications protective clothing must present a barrier to hazardous chemicals in various states, e.g., liquid, gaseous and vapor states. Important parameters in such applications include breakthrough times and permeation rates as measured for various chemicals and barrier materials. S.P. Beradinelli et al.,
am. Ind. Hyg. Assoc. J.
48 (9), pp. 804-808 (1987); J.0. Stull et al.,
Am. Ind. Hyg. Assoc. J.
51 (5), pp. 291-296 (1990).
Variation in experimental data in testing barrier materials are believed to be caused by specimen variations rather than variations in the test system. Test specimens are not in many cases inspected for small defects such as pin holes S.P. Beradinelli et al.,
Am. Ind. Hyg. Assoc. J
51 (11), pp. 595-600 (1990). Thus variations in testing can be caused by defects as well as variations in the material thickness and compositions. Beradinelli et al.,
Am. Ind. Hyg. Assoc, J.
46 (2), pp. 60-64 (1985); J.F. Stanpfers et al.,
Am. Ind. Hyg. Assoc. J.,
45 (9), pp. 642-654 (1984); S. Zing et al.,
J. Clinical Eng.
21 (6), pp. 456-465 (1996). The monitoring of defects as well as permeation of hazardous chemicals through protective barriers is essential for safety in the work place.
Estimates have been given that at least 2 million people annually are exposed to a variety of hazardous liquid chemicals. D.A. Jenien et al.,
Am. Ind. Hyg. Assoc. J.
49 (6), pp. 293-300 (1988); National Institute for Occupational Safety and Health, DHEW/NIOSH Pub. No. 74-137 U.S. Gov. Doc. Printing Office, p. 22 (1974); National Institute for Occupational Safety and Health, DHEW/NIOSH Pub. No. 749-106, Cambridge, Mass. A.D. Little, pp. 210-260 (1979). Chemical gases and vapors are routinely encountered in a number of different industries where workers must be protected by clothing impermeable to gases. Reports from three surveillance systems demonstrate 587 acute releases of hazardous materials in 1986, which resulted in 115 deaths, 2,254 injuries and 111 evacuations S. Binder et al., “Acute Hazardous Materials Release,”
Am. J. of Public Health,
vol. 79, No. 12, pp. 1681 (Dec. 1989); S. Binder,
Am. J. Public Health,
Vol. 79, No. 8, pp. 1042-1044 (Aug. 1989). Even with limited information, five states reported to the Hazardous Substances Emergency Events Surveillance (HSEES) system that for 2,391 fixed-facility events and 723 transportation-related events, 1,446 persons were injured and 11 persons killed. MMWR, CDC Surveillance Summaries, vol. 43, No. 55-2 (Jul. 22, 1994). The most frequently released hazardous substances were volatile organic compounds, herbicides, acids and ammonia
Workers involved in hazardous waste disposal have the need to be protected from a range of toxic liquids, gases and vapors. In the health care industries, inspection gloves and, in particular, surgical gloves are required to protect people from a variety of pathogenic agents. In all of the above applications, it is desirable that protective barriers be free of defects which compromise the integrity of the barrier. As such, there is a need in the art to ensure the integrity of protective barriers for the safety of well over 2 million people annually.
The evaluation of the integrity of protective clothing for industrial and medical applications has involved batch testing by electrical methods as in S. Zing et al.
J. Clinical Eng.
21 (6), pp. 456-465 (1996) and permeation as in, for example, R. Mickelsen et al.,
Am. Ind. Hyg. Assoc. J.
48 (11), pp. 941-947 (1987).
Due to potential defects during manufacturing, techniques are needed to evaluate each protective barrier on an inspection line following a manufacturing process. Some products such as condoms have a geometry which makes feasible the testing of each condom on a conductive mandrel. Condoms over a conductive mandrel placed in a conductive bath using a Q meter are described in U.S. Pat. No. 5,196,799 have been monitored for micron defects on an inspection line. Gloves have a geometry which makes impractical the testing of each glove on an inspection line using a mandrel unless a conductive mandrel is used to form the glove in the dipping process. Surgical gloves have the problem of sterilization during and after inspection. In many cases such a technique using conductive sterile baths would not be acceptable.
In chemical protective clothing (CPC), the resistance to permeation is essential to the integrity of the protective barrier. One measurement of the resistance to permeation is the breakthrough time defined as the elapsed time between initial contact of the hazardous liquid chemical with the outside surface of a protective barrier and the time at which the chemical can be detected at the inside of the barrier material. R.L. Mickelsen et al.,
Am. Ind. Hyg. Assoc. J.
48 (11), pp. 941-947 (1987). The steady state permeation rate is another measurement used in evaluating the integrity of CPC. J.F. Stanpfers et al.,
Am. Ind. Hyg. Assoc. J.,
45 (9), pp. 642-654 (1984). Permeation in barrier materials is considered to be a molecular process by which a chemical moves through a material. The process involves (i) adsorption of the chemical liquid, vapor or gas onto the material surface; (ii) difffusion through the material; and (iii) absorption from the opposite side of the material. S. Binder,
Am. J. Public Health,
vol. 79, No. 8, pp. 1042-1044 (Aug. 1989); National Institute for Occupational Safety and Health, DHEW/NIOSH Pub. No. 74-137, U.S. Gov. Doc. Printing Office, p. 22 (1974).
There have been some new approaches which attempt to overcome difficulties associated with geometry, sterilization, and various barrier materials. Stampfer et al. working with NIOSH have developed a technique for laboratory glove testing using a conductive fluid as a mandrel by filling the glove with a conductive saline solution and then placing the glove in a conductive bath. A major difficulty with this approach is there is high conductivity associated with many barriers fabricated of synthetic polymers which are very conductive, thereby making electrical measurements very insensitive.
As such, there is still a need in the art for an improved method for testing glove and other barrier materials for defects which is reliable and reproducible.


REFERENCES:
patent: 4583039 (1986-04-01), Kolcio et al.
patent: 4810971 (1989-03-01), Marable
patent: 4956635 (1990-09-01), Langdon
patent: 5059913 (1991-10-01), Nigro et al.

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