Preparation of High Hydrophilic Epoxy Resin and Its Treatment on Carbon Fiber Surface†

doi:10.7503/cjcu20160459

Abstract

Abstract:

Adipic acid modified epoxy resin(AAEP) was elaborated with adipic acid and epoxy resin using triethylamine as the catalyst. To optimize the reaction conditions, the effects of synthetic parameters were investigated on the conversion rate of adipic acid and the epoxy value of AAEP. Fourier transform infrared(FTIR) and nuclear magnetic resonance(¹H NMR) were used to characterize the chemical structures of AAEP. Then, the AAEP was neutralized with KOH to obtain the hydrophilic potassium adipic acid modified epoxy resin(AAEPK), which can be employed as a treating agent for carbon fiber(CF) in order to improve the dispersion and adhesive effect of CFs in the resin matrix. The selected concentration and adsorption amount were 1.0% and 3.0 mg/g according to the evaluation of the AAEPK emulsion properties and the CFs dispersion. In addition, the surface morphology and groups of treated CFs were assessed by Field emission scanning electron microscope(FE-SEM) and X-ray photoelectron spectroscopy(XPS). The results indicate that AAEPK is evenly distributed on the CF surface, and the dispersion of CFs in the resin matrix is improved dramatically. Furthermore, the flexural strength of treated chopped CF composite and interlaminar shear strength(ILSS) of treated CF cloth composite were proved to increase by 168% and 113%, which evaluates that the primary actions of AAEPK improving the mechanical properties of CF/epoxy resin composite was the improvement of dispersion and interface adhesive effect between CFs and the matrix.

Key words: Adipic acid, Epoxy resin, Hydrophilicity, Carbon fiber, Treating agent

CLC Number:

O631
TQ342

TrendMD:

WU Bo, ZHENG Guo, LIU Xuzhao, SUN Yu, LIU Huibing, ZHU Jiawen. Preparation of High Hydrophilic Epoxy Resin and Its Treatment on Carbon Fiber Surface^†[J]. Chem. J. Chinese Universities, 2016, 37(10): 1891.

Figures/Tables 13

Scheme 1 Preparation of AAEPK

Fig.1 Effect of molar ratio(A), reaction temperature(B), reaction time(C) and content of catalyst(D) on conversion of adipic acid and epoxy value of AAEP

Fig.2 FTIR spectra of E44 epoxy resin(a) and AAEPK(b)

Fig.3 1H NMR spectra of E44 epoxy resin(A) and AAEPK(B)The peaks are corresponding to the positions of chemical structures in Scheme 1.

Table 1 Influence of epoxy value of AAEPK on the emulsion centrifugal stability

Epoxy value/(mmol·g^-1)	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1.0
Precipitation mass/g	0	0	0	0.001	0.002	0.056	0.093	0.125	0.180

Fig.4 Influence of concentration and epoxy value of AAEPK on the emulsion surface properties(A) Surface tension; (B) contact angle.

Fig.5 Influence of epoxy value of AAEPK on the emulsion size distributionEpoxy value/(mmol·g-1): (A) 0.4; (B) 0.6; (C) 0.8; (D) 1.0. The peak values are corresponding to the peak areas.

Fig.6 Influence of adsorption amount of AAEPK on the CFs dispersion

Table 2 Element compositions of the surfaces of CF and CF-AAEPK

Sample	Element content(%)
Sample	C	O	N
CF	82.95	10.99	1.92
CF-AAEPK	72.73	22.74	1.35

Fig.7 FE-SEM images of CFs treated by AAEPKAdsorption amount of AAEPK/(mg·g-1): (A) 0; (B) 1.0; (C) 2.0; (D) 3.0; (E) 4.0; (F) 5.0.

Fig.8 C1s XPS spectra of untreated CF(A) and CF-AAEPK(B)

Fig.9 Mechanical property of CF/epoxy resin composites(A) Flexural strength of chopped CF/epoxy resin composites; (B) ILSS of CF cloth/epoxy resin composites. ILSS: interlaminar shear strength.

Fig.10 FE-SEM images of the fractured surfaces of the CF cloth/epoxy resin composites(A) CF composite; (B) AAEPK-CF composite. Insets are the partial enlangement to the FE-SM images.

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