Testing the Effectiveness of Selected Flame Retardants for Archival Cardboard Using a Medium-Scale Fire Test

Abstract Depositories of cultural institutions contain written historical documents protected by enclosures against mechanical damage, solid pollutants, the effects of light, and fluctuations in temperature and/or humidity. A potentially suitable additive flame retardant has been developed for archival cardboards to reduce the loss of valuable documents during possible fires in depositories without fixed extinguishing equipment. Archival boxes made of solid cardboard were treated with two selected additive flame retardants: a mixture of natural bentonite and mica in a cellulose ether solution and an aqueous sodium silicate solution. Subsequently a medium-scale fire test was performed on treated and untreated box samples placed in archival shelves. The test conditions simulated a fire in a relatively large depository where the oxidizing agent is present for a long time and the combustion products can leave the area. The approximate time to ignition, the decrease in mass, and the increase in temperature in various parts of the shelves were measured. The flame spreading rate was recorded and the final condition of the archival boxes and their contents was evaluated. The mixed flame retardant delayed ignition, slowed the combustion, and protected most of the archival boxes against burning; moreover, prior examination did not exhibit a substantial detrimental effect on the cardboard properties.