Q-talk 1 - Q-TIPS
- Category: Q-Talk Articles
- Published: Saturday, 28 February 1987 06:11
- Written by Jim Masal
- Hits: 1977
From Jim Masal
Another sanding device for around fillets: Buy some tubular pipe insulation foam (various diameters available), cut to a convenient size then put a piece of pipe down the middle to add stiffness. Also, Black and Decker has a hand-held belt sander (belt 3/8" x 13") that looks similar to a half-sized electric hedge trimmer that is just dandy for poking into unusual areas needing rough up work.
Gary Wilson sent some product literature on a fresh air breather system that consists of a lightweight hood with disposable, full-face visor, up to 150' of large bore hose and a portable, lightweight, electric air pump that is set away in an area of clean air. Many times more clean air is supplied than can be inhaled by the user, thus creating a slightly pressurized condition and a protective air outflow around the worker's neck. Velcro hood closures make for quick in and out. A great item to protect from paint or epoxy vapor inhalation. System lists for $497, but Gary can do better than that: Write or call, 401 College St., Bruceton, TN 38317, (901) 586-4311.
Gary also has a material called Gun Cote that he can paint your engine heads with for better heat dissipation, as he did for me. Call him for details.
Gary Wilson works with composites every day as his occupation and he was concerned enough to write up the following good advice.
SAFETY PRECAUTIONS FOR WORKING WITH COMPOSITES
Building composite aircraft presents health hazards, which are new to most homebuilders. As such, they are frequently dismissed as being minor in overall importance. Nothing could be farther from the truth. A look in SPORT AVIATION or TRADE-A-PLANE will usually find a project being sold by a builder who has become sensitized to epoxy resin systems. In nearly all cases, the sensitization can be traced to inadequate safety precautions.
By far, the most dangerous and under rated chemicals used in composite homebuilts are the epoxy and vinylester resin systems. Both present chronic as well as acute health hazards.
The epoxy systems vary greatly in their hazard potential, with Safe-T-Poxy being the safest or least dangerous likely to be encountered by the homebuilder. Even so, this does not diminish the need to maintain strict control of skin contact and respiratory exposure.
Skin contact is the most likely route of exposure to epoxy, and contact dermatitis often results. In mild forms, a red rash develops, usually accompanied by mild itching and swelling. In severe forms, this is followed by blistering, oozing, scaling and crusting of the skin. After sensitization, actual contact with the epoxy is not necessarily required to induce further attacks. Frequently, inhalation of the vapors is all that is required to induce another attack. It is obvious that adequate precautions MUST be taken BEFORE symptoms of sensitization appear.
Respiratory irritation is not as severe a problem as skin sensitization, but still requires precautions in order to maintain an adequate level of mild cough to more severe symptoms like asthma. Actual lung damage which required corrective surgery has been attributed to epoxy systems used by homebuilders.
Since the chronic effects of exposure to epoxy systems can be attributed to sensitization, strict precautions must be taken to eliminate all contact with the actual resins and hardeners as well as vapors. Skin contact can be eliminated by the use of butyl rubber gloves; barrier creams on exposed areas such as arms, and Tyvek disposable jump suits (typically referred to as moon suits). Vinyl gloves are not as suitable, as diluents will permeate them in a very short period of time. Latex gloves can be used for short periods when increased touch sensitivity is required. They also work very well as a protective cover for butyl gloves. If used without butyl gloves, they should be changed approximately every 10 minutes. Respiratory protection can be handled in one of two ways. Carbon canister respirators, typically sold for use with organics, will provide adequate protection as long as fresh carbon canisters are used. The typical useful life of a canister is 8 hours. The other method involves the use of a supplied air system. These systems take air from a known clean air source, and pump it to a mask or, preferably a full hood. With either system, the manufacturer's instructions must be followed in order to maintain full protection. The use of carbon respirators or supplied air equipment does not eliminate the need of ventilation for both health considerations as well as the buildup of flammable vapors.
The vinylesters (as on the Glasair) have the same effects as the epoxy systems, with the addition of several known carcinogens. Dimethylaniline (DMA), an accelerator, is both carcinogenic as well as a contact poison. Styrene, used as a cross linking agent, causes central nervous system damage and is carcinogenic as well. MEKP (methyl ethyl ketone peroxide), the catalyst usually used with vinylesters (and polyesters as well, ED.), is a strong oxidizer, causes chemical burns, and is known to cause gross lung hemorrhaging in test animals. As you can see, the commonly held belief that vinylester is safer than most epoxy systems is totally incorrect. The safety precautions for working with vinylesters are approximately the same as those employed with epoxy systems, except that respiratory protection becomes extremely important.
Solvents should never be used unless all previous precautions have been taken, and then only if absolutely required. The solvents typically used (acetone, MEK and others) have hazards of their own, and also act as carriers in that they speed up the absorption of resin systems through the skin, and also remove the protective oils which occur naturally in the skin.
The sanding or grinding of cured composites can liberate toxic fumes as well as particulates such as glass fibers. Because of this, the same precautions should be employed with the addition of particulate filtration. The use of mist and particulate prefilters on carbon canister respirators, or the use of disposable Tyvek suits, butyl or latex gloves, and barrier creams will provide adequate skin protection.
While it is true that certain individuals seems to be less sensitive to sensitization to epoxy systems, the effect is cumulative, and once the tolerance threshold is exceeded, the individual is sensitized for life. The carcinogenic effects of the vinylester systems are cumulative and give no warning signs until it is too late. It is obvious at this point that the safety precautions outlined are not excessive or difficult to implement. The risks involved are of such magnitude and severe consequence that to employ less stringent precautions would be extremely dangerous.
ED. NOTE: Anyone for an aluminum Q-200?
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