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. 2019 Dec 16;9(71):41603-41615.
doi: 10.1039/c9ra08098h. eCollection 2019 Dec 13.

High residue bio-based structural-functional integration epoxy and intrinsic flame retardant mechanism study

Ji Zhou  1 , Zhengguang Heng  1 , Haoruo Zhang  1 , Yang Chen  1 , Huawei Zou  1 , Mei Liang  1
Affiliations

High residue bio-based structural-functional integration epoxy and intrinsic flame retardant mechanism study

Ji Zhou et al. RSC Adv. .

Abstract

Research on structural-functional integration of polymers has become an inevitable trend and development orientation in modern materials science. An intrinsic flame-retardant epoxy with superior mechanical properties and reusability is of great application value as a composite matrix and structural material. We newly synthesized two bio-based epoxy resins, VSE and VDE, the Young's modulus of product cured by DDM (4,4-diaminodiphenyl methane) achieve 5013 MPa and 4869 MPa, respectively. The LOI values of VSE and VDE were 38.7% and 34.5% respectively and both meet UL-94 V-0 rating. High char residue at 800 °C (34.5% and 28.0%, respectively) means a superior thermal stability which conventional epoxies are unreachable. Besides, cured VDE have convenient processability which can be re-shape as heating up and retain complete structural performance after cooling to room temperature. Furthermore, thermogravimetric analysis coupled with infrared spectroscopy (TGA-IR) and energy dispersive X-ray spectroscopy (EDS) were used to assist scanning electron microscopy (SEM) to investigate the intrinsic flame-retardant mechanism. In this work, the effect and process of nitrogen-phosphorus synergy on flame retardant is revealed finally. These results indicate the newly prepared epoxy has excellent flame retardancy, mechanical properties and recyclability which opens new possibilities in practical applications of epoxy such as coatings, potting or composite matrix in the near future.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Scheme 1
Scheme 1. The synthesis of Vscb and VDP.
Scheme 2
Scheme 2. The synthesis of VSE and VDE.
Fig. 1
Fig. 1. FTIR spectra of Vscb, VSE, VDP and VDE scanned from 500–4000 cm−1.
Fig. 2
Fig. 2. 1H NMR spectra of (a)Vscb (b)VDP after purification, DMSO-d6 as solvent.
Fig. 3
Fig. 3. ESI-MS spectra of (a) Vscb (b) VDP, data from LC-MS, the separating resolution for chromatographic peak is good.
Fig. 4
Fig. 4. TG and DTG curves for cured DGEBA, VSE and VDE from 40 °C to 200 °C under N2, purge gas velocity is 100 ml min−1.
Fig. 5
Fig. 5. Time dependent FTIR waterfall curves of cured (a) E51, (b) VSE and (c) VDE combined with (d) TGA curves. The sampling interval is 40.84 s, the IR scanning range is from 400 to 4000 cm−1 and the temperature range for TGA is from 40 to 800 °C.
Fig. 6
Fig. 6. Column chart of (a) LOI values and UL94 rating (b) Young's modulus for cured E51, VSE and VDE.
Fig. 7
Fig. 7. SEM photographs of the frontmost char layer.
Fig. 8
Fig. 8. SEM photographs of the backside of frontmost char layer.
Fig. 9
Fig. 9. SEM photographs of adjacent surface below the frontmost layer.
Fig. 10
Fig. 10. EDS spectrum of char layer from the residue and the adjacent surface below the frontmost char layer.
Fig. 11
Fig. 11. A photo of the epoxy resin cured spline reshaped after heating.
Fig. 12
Fig. 12. DGEBA/DDM and VDE/DDM amorphous cell model by molecular dynamics (MD) simulation.
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