Flame-Retardant Performance of Epoxy Resin Composites with SiO2 Nanoparticles and Phenethyl-Bridged DOPO Derivative

Innovative Materials Based on Epoxy Resin for Use as Seat Elements in Bulk Transport

The subject of this research is the development of epoxy composites with a defined service life for the purpose of seat elements in rail vehicles, which will be more environmentally friendly. The produced materials based on epoxy resin filled with PLA or PLA and quercetin were subjected to solar aging tests for 800 h to investigate the impact of the additives used on the aging behavior of the epoxy matrix. Firstly, the TGA analysis showed that the use of the proposed additives allowed for the maintenance of the thermal stability of the epoxy resin. Moreover, based on an optical microscopy test, it was noticed that the introduction of PLA and PLA with quercetin did not contribute to an increase in matrix defects. The one-directional tensile tests carried out before and after solar aging showed that the presence of polylactide in epoxy composites causes a slight growth of the stiffness and strength. Based on contact angle and color change measurements, it was found that quercetin was oxidized, thus ensuring protection for the epoxy matrix. This phenomenon was confirmed by FTIR study, where the carbonyl index (CI) value for the R-PLA-Q composite was lower than for the reference sample. The obtained composite structures may be a good alternative to traditionally used systems as seat elements in rail vehicles, which are not only characterized by high aging resistance but are also more eco-friendly.

One-Pot Synthesis of Cyclomatrix-Type Polyphosphazene Microspheres and Their High Thermal Stability

Highly cross-linked inorganic and organic hybrid cyclomatrix-polyphosphazenes microspheres (C-PPZs) have been successfully synthesized by a one-pot polymerization technique between hexachlorocyclotriphosphazene and p-phenylenediamine in the presence of triethylamine (TEA), and they were used for enhancing the flame retardancy of epoxy resins (EPs). A thermoset EP was prepared by incorporating different percentages (2, 5, and 10%) of C-PPZs into diglycidyl ether of bisphenol A (DGEBA). The results reveal that the size and morphology of the microspheres can be tuned by varying the synthesis temperature. The average size of C-CPPZs gradually increased from 3.1, 4.9, to 7.8 μm as the temperature was increased from 100, 120, to 200 °C, respectively. The thermogravimetric analysis showed that the C-CPPZ microspheres have good thermal stability up to 900 °C with about ∼10 wt % mass loss for C-CPPZs formed at 200 °C compared to ∼30 wt % mass loss for those obtained at 100 and 120 °C. The 10% loss at 900 °C is much lower than the previous research concerning the thermal stability of cyclophosphazene, in which more weight losses were observed at lower temperatures. The resulting C-CPPZ microspheres were characterized by spectroscopic and imaging techniques including Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental mapping, and X-ray photoelectron spectroscopy.

The Effect of Alkyl Terminal Chain Length of Schiff-Based Cyclotriphosphazene Derivatives towards Epoxy Resins on Flame Retardancy and Mechanical Properties

A series of Schiff-based cyclotriphosphazenes with different alkyl chain length terminal ends, 4a (dodecyl) and 4b (tetradecyl), were synthesized and the structures were characterized using Fourier-transform infrared spectroscopy (FT-IR), and 1H, 13C, and 31P nuclear magnetic resonance (NMR) and carbon, hydrogen, and nitrogen (CHN) elemental analysis. The flame-retardant and mechanical properties of the epoxy resin (EP) matrix were examined. The limiting oxygen index (LOI) of 4a (26.55%) and 4b (26.71%) revealed a good increment compared to pure EP (22.75%). The LOI results corresponded to their thermal behavior studied using thermogravimetric analysis (TGA) and the char residue analyzed under field emission scanning electron microscopy (FESEM). The mechanical properties of EP showed a positive impact on tensile strength with a trend of EP < 4a < 4b. The tensile strength went from 8.06 N/mm2 (pure EP) to 14.36 and 20.37 N/mm2, indicating that the additives were compatible with epoxy resin.

Effect of Different Pre-Treatment on the Microstructure and Intumescent Properties of Rice Husk Ash-Based Geopolymer Hybrid Coating

Despite the growing popularity of rice husk ash (RHA) in various applications, limited research has been devoted to identify the influence of silica content in RHA on the intumescent properties. The present work aims to introduce a novel and economical geopolymer hybrid fire retardant coating by utilizing the use of RHA. The silica from Rice husk (RH) was extracted using distilled water and hydrochloric acid as leaching agents and subjected to pyrolysis treatment. X-ray fluorescence (XRF) analysis indicated that RH that underwent HCl pre-treatment at 600 °C for one hour produced a high purity amorphous silica content of 93.92%. XRD measurements revealed that HCl pretreatment increased the crystallization temperature of RHA to 1000 °C and retained the amorphous state of silica for 2 h. In a fire resistance test, temperature at the equilibrium and time taken to reach 200 °C for sample S3 (93.92% wt. silica) showed 5.83% and 3.48% improvement compared to sample S1 (87.49% wt. silica). The microstructure analysis showed that sample S1 possessed bigger pores on the coating surface while an increment in silica content in sample S3 produced a dense foam structure. Results from a fire resistance test were supported by the Energy dispersive X-ray (EDX) analysis of the sample. The oxygen-to-carbon ratio of S1 and S3 coating samples were 1.695 and 1.622 respectively, which indicated that lower oxygen-to-carbon ratio in sample S3 coating resulted in better anti-oxidant properties. Interestingly, the increment of SiO₂ content in RHA efficiently improved the compactness of the char layer, which resulted in a relatively higher fire-retardant efficiency. RHA proved to be a promising environmentally friendly strategy to replace halogenated fire retardant materials.

Flame-retardant activity of ternary integrated modified boron nitride nanosheets to epoxy resin

In order to improve the fire safety of epoxy resin, ZIF-8 nanoparticle in-situ decorated boron nitride nanosheet (BN-OH/ZIF-8) is fabricated via self-assembly method and then ternary integrated BN-OH/ZIF-8/PA hybrids are prepared through the chemical etching effect of phytic acid. FTIR, XRD, XPS, TEM and TGA measurements are used to characterize the structure and morphology of the nanohybrids. The researches show that BN-OH/ZIF-8/PA not only uniformly distributed in EP matrix, but also improve the thermal stability of EP. The peak heat release rate, peak smoke production rate, total smoke production values, the fire growth index and peak CO production rate obtained from cone test are significantly decreased, demonstrating the reduction of the fire hazards of EP composites containing BN-OH/ZIF-8/PA. The nano barrier effect and catalytic activity of BN-OH/ZIF-8/PA may be conducive to suppress the release of combustible volatile products and heat, facilitate the formation of graphitized carbon layer, and protect matrix from flame damage. The ternary integrated method developed in this study explores a new way to improve the flame retardant properties of EP, thereby promoting its application range.

Synthesis, Structures, and Properties of a New Pentaerythritol-Derived Flame Retardant Used in Polyamide 66

A melting phosphorous-based flame retardant (FR) named as diphenyl phosphoryl (DPP)-PEPA is synthesized from 2,6,7-trioxa-1-phosphabicyclo-(2.2.2)-octane-4-methanol (PEPA) and diphenyl phosphoryl chloride. The melting DPP-PEPA FR possesses high thermostability with T _5wt% at 344 °C, which can match the melt-spinning of engineering plastics at high temperatures. The structure of DPP-PEPA is defined by nuclear magnetic resonance and infrared spectrometry. The influences of DPP-PEPA on polyamide 6,6 (PA66) are assessed in terms of rheology parameters and crystallinity. It is observed that the flame retardancy of PA66 is greatly improved when DPP-PEPA is added to the PA66 resin. The results show that the modified PA66 has limited oxygen index as high as 29.4%, and the compact char layers are obviously formed on top of the burned samples. As compared to the pure PA66, the peak heat release rate and the average effective heat of combustion are decreased by 26.5 and 19.3%, respectively. It is obtained that the value of flame retardancy index is 1.4, indicating high efficiency of the entire flame retardancy. Moreover, pyrolysis of DPP-PEPA is carried out at different temperatures for identifying gaseous products and types of flame retardancy.