Fabrication of diatomite‐based microencapsulated flame retardant and its improved fire safety of unsaturated polyester resin

Abstract

To achive excellent fire resistance, new microcapsule flame retardants (DMCAD and DMPPD) were prepared using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide combined with melamine cyanurate or melamine polyphosphate as the shell material and diatomite as the core material. The successful assembly of DMCAD and DMPPD was detailed characterized by Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Meanwhile, the flame retardancy and thermal stability of the unsaturated polyester resin (UPR)/DMCAD and UPR/DMPPD composites were also studied. The addition of DMCAD and DMPPD effectively improves the flame retardance properties of UPR, and the effect of DMPPD was better. The limiting oxygen index (LOI) of UPR/DMPPD-3 increased by 11.6% when compared with that of UPR, and the sample achieved V-0 rating. Moreover, the peak heat release rate (pHRR) and the total heat release (THR) rate of UPR/DMPPD-3 were reduced by 67% and 26%, respectively. Under nitrogen condition and air condition, UPR/DMPPD showed better thermal stability and char-forming ability from the thermogravimetric (TG) results. Residual char of the UPR composites was systematically analyzed with SEM and XPS. Finally, the flame retardant mechanism of DMPPD was proposed. K E Y W O R D S diatomite, flame retardancy, microencapsulation, unsaturated polyester resin 1 | INTRODUCTION Unsaturated polyester resin (UPR) is widely used in transportation,chemical production, construction, sports, clothing, and other fields because of its convenient processing, low raw material cost, good water and chemical resistance, etc. 1-3 However, wider application of UPR is limited due to its extremely flammable properties during combustion. Therefore, improving the flame retardancy of UPR can further expand its application. In the last decades, halogen-based flame retardants have been widely applied but their pollution and toxicity limit their large-scale application. 4 Presently, environmentally halogen-free flame retardants have attracted widespread attention. In particular, the phosphorus and phosphorus-nitrogen containing flame retardants are mainly used as intumescent flame retardants (IFRs), which produce fewer toxic gases and smoke than halogen-based flame retardants. 5,6 Melamine (Mel) and its derivatives are promising candidates, for they are effective, economical, and environmentally friendly. Mel cyanurate (MCA) is a popular Mel-based flame retardant, which has significant advantages for its low cost, high nitrogen content, noncorrosiveness, and nontoxicity. 7 The nitrogen-containing inert gas generated by MCA during combustion can effectively dilute

Enhancement of fire safety in epoxy resin composites through incorporation of microencapsulated diatomite

“…Chen et al utilized DIA coated with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and melamine cyanurate or melamine polyphosphate to enhance flame retardancy in unsaturated polyester. Chen et al 44 achieved a modest 26.4% reduction in THR for unsaturated polyester at 20 wt %, while our work demonstrated a notable 47.8% reduction in THR for EP. These results emphasize the efficacy of DIA@PEGP as a flame retardant, significantly reducing the combustion hazard in EP.…”

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

“…To further investigate the state of different elements in residues, the peaks of each element of L7 were resolved, shown in Figure 7B–D. Five peaks at 288.3, 286.5, 285.4, 285.1, and 284.5 eV can be observed in Figure 7B, which are attributed to CO, CN, CO, CC, and CH, respectively, corresponding to the data in the existing literature 29 . In Figure 7C, the N 1s spectrum is split into three peaks, with the peaks at 401.8, 400.5, and 399.1 eV attributed to NH, CN and CN separately.…”

Fire-retardant unsaturated polyester thermosets: The state-of-the-art, challenges and opportunities

“…The cone calorimetry results revealed 67.1 % and 26.4% reduction of PHRR and THR for UP with 25% of DMPPD while UP/25 DMCAD produced a lower reduction of PHRR and THR of 45.4% and 14.5%, respectively [107] (Fig. 9d).…”

“…By incorporating 25 wt% of DMPPD (diatomite (DIA) as a core, melamine pyrophosphate (MPP) as the first shell and DOPO as second shell layer as shown in Fig. 9b) the LOI increased to 29.5% and achieved V-0 rating using the UL-94 test [107]. While incorporating 25 wt% of DMCAD (diatomite (DIA) as a core, melamine cyanurate (MCA) as the first shell and DOPO as second shell layer as shown in Fig.…”