Document bBGR3OrVBOD6V7080z7ReKKXZ

Industrial Hygiene Jour) Health Hazards and Control of an Epoxy Resin Operation W. H. KINGSLEY Sandia Corporation, Albuquerque, New Mexico THE EPOXY resins are strong and resilient most of the allergies); (3) wash hands with soa] plastics that have interested engineers since and water if uncured material is touched; they first appeared in 1950. Thermosetting andtake showers at the end of the shift; (5) cover thi heat-resistant, these plastics when cast and floor or work benches with heavy butcher papej heat-cured are especially useful in applications wherever the uncured material is being mixed requiring resistance to shock and vibration. handled; (6) wear rubber gloves during all w< They are also--unfortunately--somewhat toxic, layup operations; and (7) do not smoke or eat ii since tertiary and tetra-amines released during the area where layups are being made. the uncured, or wet, state cause allergic reactions Alleviation of the problem was also sougl in almost all personnel exposed. The epoxy resins through improvements to ventilation in are therefore an industrial hygiene problem of plastics shop, which at the time was small ai some importance; a problem that, unless non crowded. However, the industrial hygiene divi toxic hardeners are developed, can be expected sion found that since exhaust air was large! to increase as these resins come into wider and overbalanced by supplied air, eddying could wider use. An excellent paper discussing experi be prevented and thus a draft could not mental data and chemical characteristics of many maintained away from workers. Because woi of the epoxy resins appears in the February..issue on epoxy resins was thought to be exploratoi of the A.M.A. Archives of Industrial Health. only and probably temporary, approval co> When epoxy resins were first investigated by not be obtained for a program to improve venti Sandia Corporation, the ordnance contractor to tion and other working conditions. the Atomic Energy Commission, nothing was That personal hygiene and care in hand! known of their toxic effects. The first indication were not sufficient became clear as one after of toxicity occurred in January 1951 and appeared other of the plastics shop personnel becai as an inflammation of the eyes and forearms of a sensitized. Although some improvements w< plastics shop employee. In the procedure used made to the ventilation and personnel coopera Figure 2. Plastics sho at that time, the plastic was poured over fiberglas formed on a solid mold and, if necessary, was smoothed with the hand; the procedure had been used for a number of years with polyester resins with only occasional cases of dermatitis, primarily because of carelessness while handling cleaning solvents. The inflammation was therefore diag nosed at first as no more than a contact condition, and the employee was temporarily withdrawn from work on plastics. Recurrence of the condi tion when the employee returned, even though he cooperated fully in avoiding contact, was the first suggestion that epoxy resins were hyperal lergens and thus an industrial hygiene problem. Plastics shop personnel, on this indication, were then advised to follow a precautionary program such as is used in radiochemistry labora tories, that is: (1) put on clean coveralls each morning and observe extreme personal cleanli ness; (2) keep hands out of the solvents being used to clean up tools or spills (contact with plastic solvents is believed to be responsible for fully, the allergies continued--not by din contacts but by fumes of the amines given haust facilities desirec by the wet plastic. The allergies also tended iailable, some of the desi: cause a sensitization to the formerly innocuo ^industrial hygienists. polyester resins. One of the principal des As the epoxy resins received greater attentio; Jgparation of operations from development engineers and the "temporar Evolved from those in whic work continued, almost two-thirds of the pe, , were handled. This desig sonnel became sensitized. Drastic action w _ .jtwo reasons: (1) uncure precipitated finally when an order for some vcgj. . confined to areas where large shapes was received. The industrial hygh X handling equipment was division, after reviewing the procedure requiie ; area where dry material oi closed the shop until adequate space and venti J;-1 provide an area in which tion could be provided. After management was informed of the ]>: cotne sensitized could stil | " blent permitted the retenl situation and the situation that could be exper who would otherwise have if operations continued without improvemetv ..` Figures 1 and 2 show approval for a new area with much more spnj and much better facilities was obtained. Setti up the new area afforded an opportunity to p I "The area in which dry ope '-'is shown in Figure 1. Figi wall and bake-out oven in operations with industrial hygiene requireim'U! hiay be evolved which w< JSfea. fully in mind. Since not all the ducting a m of an \ Industrial Hygiene Journal 259 The exhaust system has a total capacity of about 60,000 cubic feet per minute. An input system with a capacity of 50,000 cubic feet per minute provides makeup air to replace that exhausted. This makeup air is supplied through the overhead ducts visible in the two figures. One change to the exhaust system was made ; (3) wash hands with soap d material is touched; (4) ad of the shift; (5) cover the 3 with heavy butcher paper 1 material is being mixed or lbber gloves during all wet 1 (7) do not smoke or eat in s are being made. = problem was also sought nts to ventilation in the at the time was small and the industrial hygiene divi ce exhaust air was large! plied air, eddying could not; thus a draft could not om workers. Because wor) s thought to be exploratory- temporary, approval could| program to improve ventila-J ing conditions, giene and care in handlini ecame clear as one after thi ;ics shop personnel becami l some improvements wen ion and personnel cooperate; continued--not by direct mes of the amines given oi The allergies also tended a to the formerly innocuoui facilities desired were commercially (liable, some of the design work was also done industrial hygienists. Ine of the principal design considerations was ns received greater attentioi ngineers and the "temporary j&ration of operations in which fumes__ |ved from those in which the dry plastics only most two-thirds of the pei *e handled. This design was undertaken for sitized. Drastic action wa reasons: (1) uncured material could be when an order for some vei ned to areas where special exhaust and reived. The industrial hygiem ling equipment was available, and (2) the wing the procedure require^ where dry material only was handled would U adequate space and ventila-1 vide an area in which personnel who had be- Jed. K .. fie sensitized could still work. This arrange- nt was informed of the it permitted the retention of several workers tuation that could be expect ed| o would otherwise have had to be transferred. inued without improvement]: 'v'niTigures 1 and 2 show the new plastics shop. T area with much more spacdj p area in which dry operations are carried out icilities was obtained. Setti n VtifeSMown in Figure 1. Figure 2 shows the water- forded an opportunity to pled .SSM'l and bake-out oven in the area where fumes iustrial hygiene requirementaf .'.liia.v bn evolved which we call the "wet layup" ice not all the ducting ancf 5 "iftrea. Figure 3. Fifty-ton press Figure 4. Down-draft table 260 after these photographs were taken. With ex haust blowers located, as shown, near the input to the duct, duct pressure was greater than room pressure and any leakage in ductwork resulted in pumping of amine fumes back into the shop over a period of time. Blowers have therefore been located near the outlet so that negative duct pressure is maintained. The major feature of the area in which wet plastics are handled is the water-wall in Figure 2. This area is 15 feet deep from the water tank to the outer edge of the hood. Exhaust capacity is 24,000 cubic feet per minute. All mixing and wet layup are done in this area. Workers in this area wear surgical gloves taped to their coverall sleeves to ensure that hands and arms do not come in contact with the plastic; goggles and safety glasses need not be worn. When there is no possibility of splashing of solvent or plastic, wet layup may be carried out without these safety devices, which are required elsewhere in Sandia Corporation on all machining and chemical operations. This procedure was begun after it was observed that inflammation and irritation from epoxy resins was worse when these safety devices were worn, apparently because of the concentration of fumes behind the safety glasses or face shields. Since resin spills are an important source of inadvertent contacts, cleanliness in the area is essential. In the water-wall area not only is butcher paper used under the mold but the floor covering, a plastic film, is scraped off and replaced once a month. Figure 3 shows a 50-ton press in which some curing operations are carried out and which therefore requires an exhaust system. Since the top bed of the press moves up and down, flexible ductwork was required. The press had to be further modified by the addition of sheet-metal panels to restrict the flow of air to the immediate area around the plastic. Figure 4 shows a down-draft table with a rotat ing top. In addition to the flow of air through the top grate, air may be drawn across the work when the square panel in the front of the unit is re moved. Baffles are provided in this outlet so that the down-draft flow is not stopped when the panel is removed. After the improvements were completed, no cases of sensitization occurred in the plastics shop. The few cases that have occurred at Sandia; Corporation were the result either of carelessness in handling or of working in areas that were, not approved. 1 In summary, the experience of Sandia Corpora| tion in its work with the epoxy resins suggests) the following recommendations: | (1) High standards of both personal and woi k| area cleanliness must be maintained. The worl| HYGIENIC area must be kept free of spills; when spills do occur, they must be cleaned up immediately. (2) Personnel should be made well aware o| [effects of the material with which they an| JK.-l, Hygienic Standards l A. Recommended mas working. The responsibility to ensure that pe sonnel are educated in the characteristics of till ^material will belong to both the industrial hygie ist and the plastics shop supervisor. (3) Both the industrial hygienist and th? supervisor should be able to recognize the earl; symptoms of sensitization. Personnel with tb symptoms should report immediately to th! industrial physician, since early diagnosis ani treatment are important. (4) In . a large plant or laboratory, persona outside the plastics shop must be made awai by industrial hygienists of the potential hazari of the epoxy resins and warned not to begj small operations with these plastics withoi adequate safeguards. In Sandia Corporation t] information and other industrial hygiene info: tion is distributed plant-wide in "Indust: Hygiene Bulletins." Although proper industrial hygiene practici come close to eliminating the epoxy resins as health hazard, an even more hopeful approach the substitution of low-toxicity aliphatic aminj for the toxic agents. In a recent article2 Ingbe: man, Walton, Pitt, and Paul indicate that tl hydroxyalkyl hardeners do not cause sensiti tions. Progress in this area may sometime redui or eliminate the problem. Until that time, ho ever, the epoxy resins must continue to warn the attention of the industrial hygienist. References M | CONCENTRATION (8 | vapor per million pa | (ppm).1 One part j been recommended.1 ) experience and mod i necessary for confirm * (1) Basis for Recoi V studies and lim | industry.1,2'4 B. Severity of hazari I (1) Health: High f f chronic exposure ?: a strong respirat I Acute exposures ! bronchitis and p Symptoms can i recovery may b occurred.2 Sym : affected workers ; ing, respiratory ' charge, eye an j These probably t acute exposures. ' may cause chron (2) Fire and Explos ' when concentrat per cent.1 Explo when chlorine die materials. Explo; caused by sparks partial pressure Will detonate i 100C. 1. Hine, C. H., Kodama, J. K, Anderson, H. H., Simonsoi] D. W., and Wellington, M. D.: The toxicology of epoi resins. A. M. A. Arch, of Ind. Health, 17: 129-143 (Feb. 195 2. Ingbekman, A. K., Walton, R. K., Pitt, C. F., and Pau^( M. N.: Low-toxicity aliphatic amines as cross-linking agenjj for polyepoxy resins. Ind. Eng. Ckem., 4$: 1105 (July 1957] . Short exposure ti p exposures of rats to e ; hours daily resulted : exposure to approxii hours daily for 10 wee effect.1 Animals sui posures to 20 ppm, exhibited symptoms, ppm is irritating and (1 fatal) resulted fi than 19 ppm.2