Abstract
The aim of this work is to describe the changes in the properties of ceramifiable silicone rubber-based composites caused by the incorporation of novel alternative minerals in comparison to other popular, widely utilized fillers. TiO2, calcined kaolin and calcium-based minerals mix (CbMix) consisting of CaO (6.26 wt%), CaCO3 (26.18 wt%) and Ca(OH)2 (67.56 wt%) have not been considered as a dispersed phase of ceramifiable silicone composites destined for wire covers yet. Mineral fillers: TiO2 (anatase), mica (phlogopite), CbMix, CaCO3, Al(OH)3, kaolin and calcined kaolin affect the processing and the various properties of silicone rubber-based composites destined for wire covers differently. The properties—flammability, smoke intensity, micromorphology and mechanical durability after ceramification—are assessed by measuring: the kinetics of vulcanization, stress at different levels of elongation, tensile strength and the elongation at break of the materials. Although the curing process of the composites is disturbed by the addition of CbMix, it benefits from an increase in oxygen index value, which reaches 31.4%. What is more, also its flammability parameters measured by cone calorimetry improve, such as the total heat released (THR) reaching 9.3 MJ/m2. Samples containing kaolin and calcined kaolin exhibit the best mechanical properties before ceramification, whereas composites filled with calcium-based powders (CbMix, CaCO3) mechanically display the strongest mineral char after heat treatment, possibly due to a more homogenous micromorphology and the creation of calcium silicates at elevated temperature. Significant amounts of wollastonite, parawollastonite and pseudowollastonite are visible in their structure after ceramification.
Highlights
Ceramifiable covers manufacturing technology has been known since the beginning of the 1980s, the demand for those materials increased only at the end of the 20th century when the need for maintaining integrity of fire-alarm wiring in fire was described in the US National Fire Alarm Code (NFPA 72-1999; USA)
This study focuses on the effect of unmodified mineral fillers on flammability, smoke emission and ceramification performance of ceramifiable silicone composites taking into account their processability, utilization and mechanical properties prior to fire and heat treatment
The results obtained demonstrate that addition of calcium-based minerals mix (CbMix) can significantly affect the kinetics of the mix vulcanization or even prevent it, especially after long time of storage
Summary
Ceramifiable ( called: ceramizable) covers manufacturing technology has been known since the beginning of the 1980s, the demand for those materials increased only at the end of the 20th century when the need for maintaining integrity of fire-alarm wiring in fire was described in the US National Fire Alarm Code (NFPA 72-1999; USA). In the presence of flame and elevated temperature, ceramifiable composites are able to create a mechanically resistant and porous ceramic structure maintaining the integrity of an electric circuit for 120 min, and even longer Those materials have become very popular in cable industry due to their ability to protect copper wire from extensive heat during fire as well as their high flame retardancy. Ghane et al indicated that presence of ceramic layer decreases heat transfer through flexible materials [4] The mechanisms of their ceramification, especially the involvement of various types of fillers, have been described in the literature on the subject by Hamdani-Devarennes et al who compared calcium and aluminum-based fillers as main-refractory fillers for ceramifiable composites. It is crucial to develop composite materials which are able to ceramify successfully under a wide range of thermal conditions, taking into account such variables as the temperature, heating rate, type of an atmosphere, possible external stress and the effect of thermal conductivity of inner copper core, which plays a significant role in fire spreading along the cable [24]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
