Pickering Emulsions And Polymeric Foams Based On Benzoxazine Resin

Benzoxazine resin is a newly developed phenolic resin, having a wide range of advanced features than classic phenolic resin. Among these features, its wide molecule design flexibility recently attracted significant attention, as it provided a facile method to prepare various benozxazine-based composites. As a result, functional groups which could improve the polymer’s toughness and thermal properties as well as functional groups with color changing, magnetic and conduct properties were introduced into benzoxazine molecule. Therefore, functional materials which are based on benzoxazine exhibit great application potential in different areas. By employing benzoxazine chemical synthesis, we successfully prepared the benzoxazine-based Pickering emulsions and polymeric foams, and discovered their properties. The aim of this study is to explore the functionalization of benzoxazine and broaden the application of benzoxazine resin. The primary content of the study and the results are shown as follows:1 The benzoxazine monomer bearing phenolphthalein and alkoxysilane groups was synthesized using phenolphthalein,3-aminopropyltriethoxysilane, and formaldehyde as raw materials via Mannich reaction. After hydrolysis and condensation of alkoxysilane group, the novel polysiloxane microsphere bearing phenolphthalein group (PMP) was synthesized. Furthermore, toluene-in-water Pickering emulsion using PMP as particulate emulsifier was prepared. Fourier transform infrared (FTIR) spectroscopy confirmed the existence of phenolphthalein and oxazine structures in PMP. Dynamic light scattering (DLS) indicated the average diameter of PMP was 208 nm and transmission electron microscopy (TEM) revealed the PMP shape was spherical. Due to introducing phenolphthalein structure, stable toluene-in-water Pickering emulsion presented the color changing behavior in the pH range of 9-12. It also exhibited doubly pH-responsive property:two emulsification/demulsification transitions occurred at pH 9 and 12, respectively. In addition, the emulsion achieved five and three emulsification/demulsification cycles at pH 9 and 12, respectively.2 The di-amine benzoxazine monomer was synthesized using phenol, 4,4-Diaminodiphenyl methane and formaldehyde as raw materials via Mannich reaction. Futhermore, by applying different content of azodicarbonamide as the blowing agent. As a result, benzoxazine foams with various densities were prepared. Differential scanning calorimetry (DSC) was used to monitor the foaming process. Dynamic mechanical analysis (DMA) and thermogravimetric Analysis (TGA) was carried out to testify the thermal properties of benzoxazine foam. Results showed that foam density decreased with the increasing blowing agent content. The glass transition temperature (Tg) was 220℃, char yield of the foam was 48%. Benzoxazine foam exhibited good mechanical property, the highest compress strength was 28MPa.3 Benzoxazine monomer modified by PDMS was synthesized using biphenol-A, formaldehyde and codiamine containing bis(aminopropyl)polydimethylsiloxane (PDMS) and methylenedianiline (MDA). The elongation at break and viscosity of this resin was measured, results show that the introduction of PDMS increased the toughness and process ability of benzoxazine resin. After foaming, dynamic mechanical analysis (DMA) and thermogravimetric Analysis (TGA) was carried out to testify the thermal properties of benzoxazine foam. When PDMS:MDA=7:3, the benzoxazine foam got the highest Tg of 242℃ with the char yield of 52%. Mechanical properties test proved that the toughness of these benzoxazine greatly improved.