Unleashing the power of SAN: Innovative in situ fibrillation and moisture-crosslinking techniques yield stronger, tougher, and Greener material than ABS

Abstract

Styrene-acrylonitrile (SAN) is widely used in various applications due to its excellent properties, including thermal stability, dimensional stability, and chemical resistance. However, poor toughness has limited its applications. In this study, an innovative in-situ fibrillation technique was employed to create nanofibers of thermoplastic polyurethane (TPU) in the SAN matrix. Silane was initially grafted onto TPU, followed by the development of nanofibril TPU, and lastly, post-crosslinking was conducted to retain the nanofibril structure. The grafting reaction was analyzed using Fourier Transform Infrared Spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance Spectroscopy (1H NMR). FTIR and NMR data were used in conjunction with the gel content test to confirm the involved grafting, hydrolysis, and crosslinking reactions. Observations with a Scanning Electron Microscope (SEM) revealed the formation of nanoscale TPU fibers ranging from 90 to 360 nm for various TPU contents. Because of nanofibril TPU's high aspect ratio and the effective SAN-TPU interaction, the required TPU decreased to 1 wt%. Due to the minimal use of rubber, SAN's stiffness was not compromised and compared to pure SAN and a spherical structure with the same concentration, tensile toughness increased by 350% and 200%, respectively. The fracture mechanism was investigated for both the short and long timeframes of deformation, and several potential hypotheses were proposed. Finally, this novel toughened SAN was compared with one of the most effective toughened acrylonitrile butadiene styrene (ABS) materials that contain 40 wt% spherical butadiene rubber (BR) domains.