Synergistic Effects of Graphene and Ammonium Polyphosphate Modified with Vinyltrimethoxysilane on the Properties of High-Impact Polystyrene Composites

Facile Synthesis of Reduced-Graphene-Oxide-Modified Ammonium Polyphosphate to Enhance the Flame Retardancy, Smoke Release Suppression, and Mechanical Properties of Epoxy Resin

A unique hybridized intumescent flame retardant named reduced-graphene-oxide-modified ammonium polyphosphate (RGO-APP) was successfully synthesized via the simple hydrothermal method and reduced process. Then, the obtained RGO-APP was applied in epoxy resin (EP) for flame retardancy reinforcement. The addition of RGO-APP results in a significant reduction in heat release and smoke production from the EP, which is attributed to EP/RGO-APP producing a more compact and intumescent char against the heat transfer and combustible decomposition, thus enhancing the fire safety of EP, as confirmed by char residue analysis. Especially, the EP containing 15 wt% RGO-APP acquires a limiting oxygen index (LOI) value of 35.8% and shows a 83.6% reduction in peak heat release rate and a 74.3% reduction in peak smoke production rate compared with those of pure EP. The tensile test exhibits that the presence of RGO-APP favors the enhancement in tensile strength and elastic modulus of EP due to the good compatibility between flame retardant and epoxy matrix, as supported by differential scanning calorimetry (DSC) and scanning electron microscope (SEM) analyses. This work provides a new strategy for the modification of APP, thus facilitating a promising application in polymeric materials.

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

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.

Polymer Composites Filled with Metal Derivatives: A Review of Flame Retardants

Polymer composites filled with metal derivatives have been widely used in recent years, particularly as flame retardants, due to their superior characteristics, including high thermal behavior, low environmental degradation, and good fire resistance. The hybridization of metal and polymer composites produces various favorable properties, making them ideal materials for various advanced applications. The fire resistance performance of polymer composites can be enhanced by increasing the combustion capability of composite materials through the inclusion of metallic fireproof materials to protect the composites. The final properties of the metal-filled thermoplastic composites depend on several factors, including pore shape and distribution and morphology of metal particles. For example, fire safety equipment uses polyester thermoplastic and antimony sources with halogenated additives. The use of metals as additives in composites has captured the attention of researchers worldwide due to safety concern in consideration of people's life and public properties. This review establishes the state-of-art flame resistance properties of metals/polymer composites for numerous industrial applications.