A facile and novel modification method of β-cyclodextrin and its application in intumescent flame-retarding polypropylene with melamine phosphate and expandable graphite

In this paper, a facile and novel method was adopted in tailoring beta-cyclodextrin (CD), which can drastically improve its surface hydrophobicity and decrease its water solubility. By this way, the interfacial compatibility between CD and polypropylene (PP) is distinctly strengthened after modification that is well certified by scanning electron microscope (SEM) and molecular dynamics simulation, respectively. Surprisingly, the flame retardant properties of PP compositing with modified CD (CM) are slightly higher than that of PP/CD. Moreover, the flame retardancy of PP/CM system can be maintained after water treatment. Except that, the synergistic effect of expandable graphite (EG) on the flame retardant properties of PP/melamine phosphate (MP)/CM system were systematically investigated. It can be observed that when the content of EG is 10 wt.%, the flame retardant properties of PP system achieve 31.2 % in limiting oxygen index tests and pass UL-94 V-0 rating in vertical burning tests. And a potential condensed flame retardant mechanism was proposed in detail.