Bull. Spec. CORESTA Congress, Brighton, 1998, p. 187, ST41
Potential problems associated with cigarette coal burning under tipping paper
Papeteries de Malaucène - LTR Industries, France
Some potential problems such as appearance, smell or fire hazard, may occur when the cigarette coal burns under tipping paper. For the latest, some flammability tests, adapted to the cigarette were set up to evaluate the combustibility of tipping paper, the propensity of cone drop off, the degradation of acetate tow and the flare tendency. Filter tip flare is a small flame which occurs when the cigarette coal is under the tipping. Flare propensity is affected by many parameters, for example by the nature and level of mineral fillers used in tipping base papers and inks used for printing. Mechanisms involved in paper combustion will be reviewed. Thermal degradation of cellulosic materials may follow two different pathways : at lower temperatures (<250-300°C) dehydration occurs, leading to the formation of water, carbon monoxide, carbon dioxide and char. This is a slow reaction which is in competition with a fast one which predominates at higher temperatures (>250-300°C) and involves intramolecular transglycosylation of cellulose and leads mainly to the formation of levoglucosan which is further degraded into volatile flammable compounds. When exposed to fire, most of the flame retardants used for cellulosic materials, act in the condensed phase and favour the dehydration pathway, leading to an increase in char yield at the expense of levoglucosan and volatile compounds formation. The chemical action is not the only one available and the physical action of some fillers in paper can explain the flame retardancy. The key issue is to obtain a "non combustible" tipping paper without the drawbacks associated with some flame retardant treatment (tip flare for instance).