Fabric and Leather Waterproofing Finishes Usually Make Fast Burning Fires of High Temperature—Suggested Methods for Handling Such Fires
THERE are at present several methods of waterproofing leather and fabrics, practically all of which represent severe fire hazards in manufacturing processes as well as readily inflammable material in finished form. The more common methods of waterproofing fabrics and leather include rubber cementing, rubber spreading, rubber dipping, oil treatment, pyroxylin coating, and viscol treatment, the latter being used almost entirely for leather while the former, for fabric.
The rubber treatments are chiefly hazardous due to the presence of inflammable solvents in the process of manufacturing. In the rubber cementing process, the thin sheet rubber is cemented to the fabric by a cement which has as a solvent benzine, gasoline, or other petroleum volatile. In the spreading process, the rubber is made into a sticky mass by the use of inflammable solvents and spread over the fabric. For the dipping process, the rubber is dissolved to form a cement, into which the materials to be waterproofed are dipped.
In each of the above processes of manufacturing the hazard lies in the presence of quantities of inflammable liquids as well as inflammable vapor.
Insofar as operating on fires at which the finished articles are present, the chief trouble is the presence of dense, choking smoke from the burning rubber. Rubber, at high temperature fires, burns rapidly while throwing off its heavy pungent smoke.
The oil treatment for fabrics consists largely of applying linseed oil, or a combination of linseed oil and other materials, to the surface of the fabric. Oxidation quickly toughens the oil, leaving a rubbery waterproof substance on the fabric which provides the waterproofing.
Linseed oil in itself does not represent a severe fire hazard except insofar as its tendency to cause fires by spontaneous ignition. Once afire, linseed oil burns with no greater intensity than does crude oil. It is not kept on premises in the quantities in which crude oil is commonly found so that its hazard may be considered appreciably less. The finished articles burn rapidly, throwing off heavy smoke.
Pyroxylin coating probably constitutes the most severe fire hazard in connection with waterproofing garments. The process of coating cloth with pyroxylin, or nitro cellulose compounds, is similar to that of coating with rubber compound, but the hazard is greater fundamentally on account of the high combustibility and relative instability of pyroxylin compound as compared with rubber compound. The same hazard of volatile flammable solvent is present, though instead of gasoline or benzol, such solvents as ethyl acetate, amyl acetate, and the higher alcohols are used.
In addition to the severe hazards in the manufacturing processes, pyroxylin coated fabrics represent severe fire hazards long after manufacture. Rapid combustion and generation of high temperature may be expected.
Viscol is a patented waterproofing material for leather. Some forms of viscol are solid and in this form it is a soft elastic material somewhat resembling rubber and not very combustible. It is not subject to spontaneous ignition. In other forms it is semi-fluid. It is used principally as a waterproofing material for leathers. For this purpose it is thinned with some light oil such as kerosene or naptha. Leather is dipped into this liquid, then dried, the light oil evaporating and allowing the viscol to remain in the pores. Some forms contain no volatiles, and are not thinned. It is used chiefly in shoe factories for waterproofing soles and uppers. It is also used as a rubber substitute in the solid form. Viscol thinned with light inflammable oil should be treated as a gasoline hazard. In operating at a fire where this material is employed, great care must be exercised to prevent explosion of the vapors generated, or if there is likelihood of an explosion, to provide sufficient openings in the building to release any explosive pressures created.
The finished articles employing viscol do not represent any greater hazard than do the finished rubber articles.
Handling the Fire
If the fire occurs in the plant manufacturing waterproofed materials, the chief precaution to take is to minimize the danger of explosion of flammable vapors. With the exception of the oil skin plants, the hazard is present to a pronounced degree. Opening the building for thorough ventilation is a prime essential, all doors and windows should be opened as early as possible, and open vats covered, if covers are available. Keeping streams out of all containers of inflammable liquids is, of course, a very important precaution to take.
Where finished goods are encountered at a fire, there is one redeeming feature to be remembered: the goods are less damaged by water than would be the case where other than waterproofed articles are encountered. There may be heavy, pungent smoke, but this can easily be taken care of by proper ventilation. The use of water streams to wet down the material is the most satisfactory method of handling the blaze. This applies whether oilskins, pyroxylin, rubber or viscol coated materials are encountered.