Preparation and research of epoxy modified by carboxyl-terminated polybutylene adipate at room temperature

Abstract

In this study, carboxyl-terminated polybutylene adipate (CTPBA) was used to modify epoxy resin, and the modified epoxy resin was cured by a room temperature rapid curing agent (T-31). The effects of CTPBA modification on bonding properties and mechanical properties of epoxy resin adhesive at room temperature were carefully studied. Epoxy-terminated prepolymer was synthesized by pre-polymerization and its structure was characterized. Compared with the addition method of direct blending, the bonding properties and mechanical properties of pre-polymerized epoxy resin adhesive were significantly better. Compared with unmodified epoxy resin, CTPBA modification significantly improved the bonding strength. Furthermore, with the increase of CTPBA content, the shear strength of the material increased first and then decreased, and reached the maximum when the addition amount was 40 phr. This shows that the tensile strength of the material decreased with the increase of CTPBA content, and the elongation at break increased with the increase of CTPBA content. Dynamic mechanical analyzer (DMA) test results showed that the addition of CTPBA reduced the glass transition temperature, but broadened the damping temperature range. TG analysis showed that the thermal stability of the modified epoxy resin was good, and compared with pure epoxy resin, the initial temperature of thermal weight loss and the maximum thermal decomposition rate decreased, but the overall thermal stability was not significantly different. In summary, CTPBA modification of epoxy resin is expected to improve the comprehensive mechanical properties at room temperature.

Fig. 1. Synthesis schematic diagram of CTPBA and E-CTPBA.

Fig. 2. (a) FTIR spectra of E-51, CTPBA and E-CTPBA; (b) synthetic infrared spectra of E-CTPBA varying with time.

Fig. 3. ¹H-NMR spectra of (a) CTPBA1000 and (b) E-CTPBA1000.

Fig. 4. MALDI-TOF MS of (a) CTPBA1000 and (b) E-CTPBA1000.

Fig. 5. The curves of (a) impact strength (b) tensile shear strength (c) tensile strength and (d) elongation at break under different modification methods.

Fig. 6. Effect curve of E-CTPBA1000 addition on (a) tensile shear strength and (b) gel time.

Fig. 7. Effect curves of the E-CTPBA1000 addition on (a) tensile strength and elongation at break; (b) impact strength.

Fig. 8. SEM images of impact fracture of epoxy resin cured with different additions of E-CTPBA1000. (a) 0 phr, (b) 20 phr, (c) 40 phr, (d) 60 phr, (e) 80 phr, (f) 100 phr.

Fig. 9. Curve of E-CTPBA1000 addition to modified epoxy resin (a) tan δ–T curve, (b) storage modulus E′.

Fig. 10. Curve of E-CTPBA1000 addition to modified epoxy resin (a) TG and (b) DTG.