Preparation of hybrid silicon materials microcapsulated ammonium polyphosphate and its application in thermoplastic polyurethane

ABSTRACT Silica‐gel microencapsulated ammonium polyphosphate (SiOAPP), prepared by traditional sol–gel method, is still incompatible with polymer and easily attacked by moisture due to the presence of lots of hydroxyl group, so the traditional sol–gel method was optimized with polydimethyl siloxane (PDMS) to improve the related properties of microcapsules in this study. The results showed that the SiOAPP process and shell shape had changed significantly, and the APP microcapsules with silica/silicone carbon composite shell (SiOCAPP) was successfully prepared. The hydrophobicity of SiOCAPP was much better than that of the SiOAPP, the water contact angle of SiOAPP was 54°, while the water contact angle of SiOCAPP could reach 111°. The property reinforcements of the SiOCAPP in thermoplastic polyurethane (TPU) were studied and compared with the TPU/SiOAPP composites. The time to ignition reduced by 2 s and the maximal peak of heat release rate (pk‐HRR) increased by 4.4%, but the average heat release rate and total heat release, respectively, reduced by 15.5% and 31.4%, which was a great improvement on the flame retardancy of TPU, and the char residue rate, which is related to the condensed flame retardant effect, increased by 10%. Besides, the tensile strength and elongation at break increased by 11.8% and 5.84%, respectively. Generally, the sol–gel method modified by PDMS provided an novel method to improve the comprehensive properties of APP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45742.