Effect of cenospheric fillers on the flammability and fire hazard of silicone rubber composites

Abstract

This paper presents the results of testing the flammability of silicone rubber composites containing fillers, such as cenospheres, cenospheres covered with iron, attapulgite, wollastonite, aluminum hydroxide and silica. In order to increase the insulating character of boundary layer, boron trioxide was incorporated into the composites of silicone rubber as a ceramization additive. The flammability of the composites was tested with the use of a cone calorimeter. The composition of the gaseous products of thermal decomposition was determined quantitatively and qualitatively in the system with intensive stirring in the fluidal bed, under isothermal conditions at temperatures T = 550, 650 and 750°C. All the test results show that the fillers used, especially with ceramization additives considerably reduce the fire hazard of silicone rubber composites containing these fillers.

Effect of mineral filler additives on flammability, processing and use of silicone-based ceramifiable composites

“…Flammability of all the composites is comparable to other flame-retarded siliconebased materials presented in the literature (Table 5) [21]. It is not the low flammability that is the most important feature of the composites, but their ability to form a protective ceramic structure.…”

“…Whereas Xiong et al proposed a solid-state sintering mechanism as an explanation of highly loaded silicone composites ceramification [16]. Many studies describe effects of incorporation of different additives on properties of ceramifiable silicone composites, such as organic and mineral fibers [17], carbon fibers [18], organo-modified montmorillonites (O-MMT) [19], cenospheres covered with iron [20,21] or silsesquioxanes [22,23]. Final properties of the ceramic structure strongly depend on ceramification conditions and these may vary considerably in case of an actual fire event.…”

Impact of Basalt Filler on Thermal and Mechanical Properties, as Well as Fire Hazard, of Silicone Rubber Composites, Including Ceramizable Composites

“…Reviewing the source literature on the subject leads to the conclusion that the forces of cohesive interactions between silica particles resulting from the decomposition of SR are insufficient for the formation of a condensed boundary layer [12,25]. This is due to the fact that the obtained silica is present in the form of dust, with a low barrier factor, which is additionally easy to remove from the surface of the boundary layer through a stream of gases in the combustion zone.…”

“…The review of the source literature on the subject leads to the conclusion that the high resistance of silicones to fire is mainly related to the formation, during their thermal decomposition, of a boundary layer composed of silica with a high thermal capacity, which to a considerable degree makes conducting heat between the flame and the sample difficult. On the other hand, the cohesive forces between the particles of silica are insufficient for the formation of an effective barrier impeding the mass flow between the sample and the flame [12,13]. Hence, the formation of an insulating ceramic layer of a specific mechanical durability and which is resitant to cracking requires the introduction of particular mineral fillers into a silicone rubber SR (silicone rubber) matrix.…”

Influence of Lignocellulose Fillers on Properties Natural Rubber Composites

“…The flame-retardant effect of aluminum hydroxide, consisting in liberating water vapor, during its decomposition, diluting the flammable products of polymer decomposition, and forming a thermally stable ceramic layer as a barrier for heat and mass transport, is well known. However, the effectiveness of the ATH action is satisfactory only with a degree of filling, which negatively influence the mechanical properties of the composites containing this filler [26].…”