Thermal aging properties of flame retardant silicone rubber based on melamine cyanurate

Abstract

In this work, an efficient preparation method for flame retardant silicon rubbers (FRSR) was established with using melamine cyanurate (MCA) as flame retardants. In order to analyze the thermal aging mechanisms and flame retardancy of FRSR, cone calorimetric test (CCT), Fourier transform infrared (FTIR) spectra, scanning electronic microscopy (SEM), and energy dispersive X-ray spectra were performed. Results indicated that the aging time significantly decreases the tensile strength and the elongation at break. SEM images revealed that the porous surface of the aged FRSR provide diffusion path for heat and oxygen, which resulted in a continuously increase in Shore A hardness due to the increase of cross-linking density during the aging process. FTIR spectra further proved that the MCA is well-embedded into samples and crosslinking reaction between free radicals of silicone rubber (SR) and oxygen was occurring during the aging process. Besides, CCT results showed that all FRSR samples before and after thermal aging exhibit excellent flame retardancy with compact and stable char residue layers, effectively hindering the heat transfer and oxygen diffusion. It was expected that our findings could provide important information to fabricate SR with flame retardancy and outstanding longterm thermal-aging resistance. K E Y W O R D S ageing, degradation, mechanical properties, thermal properties 1 | INTRODUCTION Compared with general organic rubbers, silicone rubber (SR) shows excellent temperature resistance, electrical insulation, high breathability, dielectric properties, and weather resistance due to its Si-O bond on main chain with side groups including methyl, vinyl, and phenyl. 1-5 Over the past decades, SR materials have been widely used in various areas, such as medical and health, aerospace, wire and cable, automotive industry, architecture, and so on. 6-8 However, SR is flammable and can keep burning when exposed to open flames, which limits its application in the field of electronic appliances.

Synergistic flame retardant linear low‐density polyethylene based on piperazine pyrophosphate and melamine cyanurate

“…On the one hand, it destroyed the compactness of the char layer; on the other hand, the released inert gases diluted the oxygen concentration on the surface of the material and thickened the residues as a whole. 23,26,27…”

“…However, its flame retardant effect mainly depends on the gas phase and it presents a relatively poor condensed-phase charring ability when used alone. 15,[20][21][22][23] In this study, PAPP/MCA was used as a synergistic flame retardant system for the preparation of a halogen-free LLDPE composite with high flame retardancy, the fire retardancy, thermal stability and mechanical performance of the LLDPE composite were systematically investigated through the cone calorimeter, thermogravimetric infrared, and so forth, and its relevant flame retardant mechanism was further explored.…”

“…During the combustion, MCA generates lots of gas such as ammonia, which dilutes the oxygen concentration on the material surface. However, its flame retardant effect mainly depends on the gas phase and it presents a relatively poor condensed‐phase charring ability when used alone 15,20–23 …”

Synergetic Effect of α-ZrP Nanosheets and Nitrogen-Based Flame Retardants on Thermoplastic Polyurethane

“…Although in the 20th century, halogenated flame retardants (FRs) were the dominant additives to polymers to reduce their flammability, the environmental concerns upon using these additives outweigh their effectiveness in flame retardancy . Over the last decade, halogen-free flame retardants (FRs) such as nitrogen (N)-based FR, prosperous (P)-based FR, and metal hydroxides have been rapidly developed and extensively used as alternative flame retardants. − Melamine cyanurate (MCA) is an N-based FR. , It is an environmentally friendly and recyclable FR. MCA decomposes at a high temperature; thus, it can be recycled with polymers by re-extrusion .…”

“…6−8 Melamine cyanurate (MCA) is an N-based FR. 9,10 It is an environmentally friendly and recyclable FR. MCA decomposes at a high temperature; thus, it can be recycled with polymers by re-extrusion.…”