Synthesis, characteristic, and application of new flame retardant containing phosphorus, nitrogen, and silicon

Recent Developments and Research Avenues for Polymers in Electric Vehicles

Plastics have been an indispensable material of choice in automobiles with wide range of applications such as interior, exterior, under the hood, and lighting/wiring applications. The prime motive of inclusion of these materials is increase in fuel efficiency and reduction in carbon footprint by replacing the energy intensive metallic counterparts. The current decade i. e., the 2020s has seen a recent surge in the sales of electronic vehicles. Although these numbers are promising, the growth in the rest of the parts of the world is not encouraging. It is primarily due to the skepticism involving battery life and efficiency, profitability, and environmental footprint when compared to conventional and hybrid vehicles. Also, a more concerted effort is needed in the lagging areas in order to install the required infrastructure. The emergence of plastics in the development and acceptance of e-vehicles is going to be pivotal especially when the efficiency and profitability are considered as they give the required freedom to the engineers for the design and development of various parts and sizes by replacing the bulkier and more dense materials. Also, the research on bionanocomposites has received great interest from the research community due to their versatility in application along with their eco-friendly nature throughout the lifecycle starting from feedstock up to end-of-life treatment. This review paper will be one of its kind to present a critical review of the recent developments of polymers suitable for use in e-vehicles. Also, a comprehensive discussion comprising of newer research areas for polymers in their use for e-vehicles will be presented.

Preparation and Purification of a Flame-Retardant Polyphenylphosphonate Containing 4,4'-Dihydroxybenzophenone

A polyphenylphosphonate containing 4,4'-dihydroxybenzophenone was synthesized as a flame retardant. However, impurities were detected and may compromise its properties and thermal stability. Thus, a purification route based on water and hexane extraction with reflux was proposed. Results showed success in removing impurities, especially P–Cl groups, without damaging the polymer.

Synthesis of a Novel Flame Retardant Containing Phosphorus, Nitrogen, and Silicon and Its Application in Epoxy Resin

A novel flame retardant (TDA) containing phosphorus, nitrogen, and silicon was synthesized successfully via a controllable ring-opening addition reaction between 1,3,5-triglycidyl isocyanurate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 3-aminopropyltriethoxysilane, and TDA was then blended with diglycidyl ether of bisphenol A to prepare flame-retardant epoxy resins (EPs). The chemical structure and components of TDA were confirmed by Fourier transform infrared (FTIR) spectra, ³¹P nuclear magnetic resonance, and X-ray photoelectron spectroscopy. Thermogravimetric analysis results indicated that after the introduction of TDA, cured EP maintained good thermal stability with a minimum initial decomposition temperature of 337.6 °C, and the char yields of a EP/TDA-5 sample significantly increased by 76.2% compared with that of the neat EP thermoset. Additionally, with the addition of 25.0 wt % TDA (1.05 wt % phosphorus loading), the limited oxygen index value of cured EP increased from 22.5% of pure EP to 33.4%, and vertical burning V-0 rating was easily achieved. Meanwhile, after the incorporation of TDA, the total heat release and total smoke production of the EP/TDA-5 sample obviously reduced by 28.9 and 27.7% in the cone calorimeter test, respectively. Flame-retardant performances and flame-retardant mechanisms were further analyzed by scanning electron microscopy, FTIR, energy-dispersive spectrometry, and pyrolysis gas chromatography/mass spectrometry. The results reveal that the synergistic effect of phosphorus, nitrogen, and silicon plays an excellent flame-retardant role in both gaseous and condensed phases. In addition, the mechanical and dynamic mechanical properties of cured EP thermosets are well maintained rather than destroyed. All the results demonstrate that TDA endows epoxy resin with excellent flame retardancy and possesses great promise in the industrial field.

The application of a phosphorus nitrogen flame retardant curing agent in epoxy resin

In order to improve the compatibility of flame retardant and epoxy resin, a phosphorus nitrogen flame retardant curing agent poly(p-xylylenediamine spirocyclic pentaerythritol bisphosphonate) (PPXSPB) was synthesized. FTIR, 1HNMR, and mass spectroscopy were used to identify the chemical structure of PPXSPB. Epoxy resin (E-44) and PPXSPB as the raw material, a series of thermosetting systems were prepared. The effects of PPXSPB on flame retardancy, water resistance, thermal degradation behavior, mechanical properties and the adhesive strength of EP/PPXSPB thermosets were investigated. The results show that with the increase of phosphorus content, the oxygen index and carbon residue of the system both increased significantly, and the heat release rate gradually decreased, which is of great significance in delaying the occurrence of fire. When the phosphorus content is 3.24% in EP/PPXSPB thermosets, EP-2 can successfully pass the UL94 V-0 flammability rating, the LOI value of EP-2 can reach 31.4%, the impact strength and tensile strength was 6.58 kJ/m2 and 47.10 MPa respectively, and the adhesive strength was 13.79 MPa, the system presents a good overall performance.

Synergistic Effect of Hexaphenoxycyclotriphosphazene and Aluminium Tri-Hydroxide on Flame Retardancy and Smoke Suppression of Epoxy Resin

Flame retardancy and smoke suppression of polymer materials are key problems to be considered for applications that have a potential fire hazard. This study selected hexaphenoxycyclotriphosphazene (HPCTP) and aluminium tri-hydroxide (ATH) powder as an integrated flame retardant treatment in epoxy resin (EP) which is usually used as the matrix of a composite. The characteristics of flame retardancy and smoke suppression were investigated. The results showed that when treated with HPCTP and ATH, the resin exhibits superior properties, resisting flame development and smoke release. Based on analysis of the surface structure of the burned materials by scanning electron microscopy–energy dispersive spectroscopy and X-ray photoelectron spectroscopy, it was confirmed that HPCTP and ATH can attract a lot of heat to slow down decomposition of the resin and produce a comprehensive protection system consisting of a non-flammable gas and solid phases during burning. Non-flammable gas can reduce the concentration of flammable gas to inhibit combustion. In addition, H2O vapour can also reduce the concentration of flammable gas to inhibit combustion. Meanwhile, solid phase films can insulate air to slow down combustion and smoke release.

Synthesis and properties of a new halogen-free flame-retardant epoxy resin curing agent

A novel intumescent flame-retardant curing agent, poly-( meta-xylylenediamine spirocyclic pentaerythritol bisphosphonate) (PMXSPB), was synthesized and subsequently characterized using Fourier transform infrared, proton nuclear magnetic resonance, and mass spectroscopies. PMXSPB was used as a flame-retardant and curing agent for preparing halogen-free flame-retarded epoxy (EP) resins. The thermal stability, mechanical properties, flame resistance, and morphology of the char layer of flame-retarded EP resins were investigated using thermogravimetric analysis, tensile and Charpy impact tests, limiting oxygen index (LOI), the UL94 test, and scanning electron microscopy, respectively. The results demonstrated that the addition of PMXSPB improved the flame resistance of EP resin composites, and the residual char ratio at 600°C was significantly increased. The flame-retarded composites filling with 3.01% phosphorus content (EP 100 g and PMXSPB 35 g) exhibited the best combination of properties, including a higher glass transition temperature (147°C), good thermal stability, an initial weight loss temperature of 269°C, and an LOI of 31.2. The vertical burning test reached the UL94 V-0 level, and the tensile and impact strengths were 51 MPa and 4.8 kJ m−2, respectively.

Review on flammability of biofibres and biocomposites

The subject on flammability properties of natural fibre-reinforced biopolymer composites has not been broadly researched. This is not only evidenced by the minimal use of biopolymer composites and/or blends in different engineering areas where fire risk and hazard to both human and structures is of critical concern, but also the limited amount of published scientific work on the subject. Therefore, it is necessary to expand knowledge on the flammability properties of biopolymers and add value in widening the range of their application. This paper reviews the literature on the recent developments on flammability studies of bio-fibres, biopolymers and natural fibre-reinforced biocomposites. It also covers the different types of flame retardants (FRs) used and their mechanisms, and discusses the principles and methodology of various flammability testing techniques.