Effect of CTBN and Nano-SiO2 modified epoxy resin powder on the mechanical properties of cement-based composites

The high brittleness of oil well cement seriously affects the cementing quality. In order to maintain the safe and effective production of oil and gas wells, it is crucial to employ solid flexible fillers to reduce the brittleness of cement. In this study, a new type of flexible resin material (C-ER) was prepared by modifying epoxy resin with liquid nitrile butadiene rubber (CTBN) and nano-SiO2. The chemical composition, hydrophilicity, dispersibility, microstructure, and mechanical properties of C-ER were studied by FT-IR, XPS, contact angle, UV spectroscopy, SEM, DMA, and uniaxial compression. The results show that CTBN reacted with the epoxy group successfully. Due to the presence of SiO2, C-ER has good hydrophilicity and dispersion properties. The introduction of flexible segments makes C-ER have a lower modulus and crosslinking density, and its compressive elastic modulus is reduced by 47.4 % compared with pure resin. In addition, the effect of C-ER on the performance of oil well cement was tested. The results show that the addition of C-ER does not affect the fluidity of cement slurry and can improve the strain capacity of cement stone under load. Compared with blank cement and unmodified resin cement, the flexural strength of cement sample containing 4 % C-ER particles increased by 9.0 % and 25.1 %, respectively, and the elastic modulus of cement stone decreased by 31.2 % and 25.0 %, respectively. SEM images show that C-ER maintains good dispersion and bonding properties in cement matrix. C-ER can reduce the brittleness of cement effectively through its own elastic deformation and debonding to the cement matrix.