Recent Advances in Halogen-Free Flame Retardants for Polyolefin Cable Sheath Materials

Abstract

With the continuous advancements of urbanization, the demand for power cables is increasing to replace overhead lines for energy transmission and distribution. Due to undesirable scenarios, e.g., the short circuit or poor contact, the cables can cause fire. The cable sheath has a significant effect on fire expansion. Thus, it is of great significance to carry out research on flame-retardant modification for cable sheath material to prevent fire accidents. With the continuous environmental concern, polyolefin (PO) is expected to gradually replace polyvinyl chloride (PVC) for cable sheath material. Moreover, the halogen-free flame retardants (FRs), which are the focus of this paper, will replace the ones with halogen gradually. The halogen-free FRs used in PO cable sheath material can be divided into inorganic flame retardant, organic flame retardant, and intumescent flame retardant (IFR). However, most FRs will cause severe damage to the mechanical properties of the PO cable sheath material, mainly reflected in the elongation at break and tensile strength. Therefore, the cooperative modification of PO materials for flame retardancy and mechanical properties has become a research hotspot. For this review, about 240 works from the literature related to FRs used in PO materials were investigated. It is shown that the simultaneous improvement for flame retardancy and mechanical properties mainly focuses on surface treatment technology, nanotechnology, and the cooperative effect of multiple FRs. The principle is mainly to improve the compatibility of FRs with PO polymers and/or increase the efficiency of FRs.

Preparation and characterization of poly(ethylene‐co‐vinyl acetate)/high‐density polyethylene/aluminum hydroxide/clay composites by electron beam irradiation

“…In principle, these results suggest that the metal oxide and water molecules generated from the ATH protected the surface layer of the EVA/HDPE, preventing heat transfer and diluting combustible gas to provide flame retardancy during combustion. The char formed during the combustion of clays provides an effective barrier and delays further combustion 35,36 . The LOI values increased slightly with increasing clay content to 10 phr, beyond which it decreased.…”

“…The char formed during the combustion of clays provides an effective barrier and delays further combustion. 35,36 The LOI values increased slightly with increasing clay content to 10 phr, beyond which it decreased. This can be due to the poor dispersion of the clay at high content.…”

A Systematic Investigation on the Influence of Intumescent Flame Retardants on the Properties of Ethylene Vinyl Acetate (EVA)/Liner Low Density Polyethylene (LLDPE) Blends

“…In addition, the process of condensed phase forms part of the acid-promoted dehydration that causes the acceleration of the consolidated char layer formation [ 13 , 14 ]. Several systems, such as metallic hydroxide, halogen antimony, and phosphorous nitrogen, possess synergistic effects when used in the flame-retardant polymer [ 15 , 16 ].…”

Ionic liquids modified MXene as a flame retardant synergist for the unsaturated polyester resin

“…7 Compared with halogenated flame retardants, it has lower flame retardancy and poorer thermal stability. 8 Therefore, more halogen-free flame retardants must be added to achieve the same flame retardancy. However, the large addition can lead to a decrease in the physical properties of the composites.…”

“…APP is an efficient halogen‐free flame retardant with the advantages of non‐toxicity and anti‐dripping during combustion, so it is considered to be one of the most promising environment‐friendly halogens‐free flame retardants 7 . Compared with halogenated flame retardants, it has lower flame retardancy and poorer thermal stability 8 . Therefore, more halogen‐free flame retardants must be added to achieve the same flame retardancy.…”