Preparation Of Novel Green Charring Agent And Study Of Its Charring Mechanism

Intumescent flame retardant (IFR) is one of the most important research area because of itshalogen-free, low-toxic, and low emission of smoke. However, it has some weakness, such ashigh content, limted efficiency, and easy to moisture, which reduced its application area.Therefore, these problems are wating for researchers to solve. The efficiency of IFR depends onthe amounts and quality of char formation. In order to solve these problems, this thesis usehydroxyapatite (HAP), poly[cyclotriphosphazene-co-(4,4-sulfonyldiphenol)](PZS), andPhosphomolybdic acid hydrate grafted PZS(PZS-g-PMo) as the synergist, IFR(APP/PER=3/1)as the main flame retardant to achieve an flame retardancy of polypropylene(PP). Limit oxygenindex (LOI) test, UL-94test, and thermogravimetic analysis (TGA) were used to investigatetheir flame retardancy and thermal stability. The Scanned Electron Microscope SEM and X-rayphotoelectric spectroscopy (XPS) were used to evaluate the chemical structure and charmorphology of their char. Then the mechanism of flame retardant was speculated, the mainresearch contents are as follows:1) Considering its hydroxyl group in HAP, it may have a good effect on char’s formation.Then HAP/IFR was used to enhance the flame retardancy of PP. It turns out that PP compositesobtain the best flame retardancy when the mass content of HAP and IFR are0.5%and19.5%,respectively. And its LOI value is29.9%and it can pass UL-94V-0grade. In addition, the charhas a good thermal stability. Nevertheless, as the content of HAP increases, the flameretardancy of PP composites starts to decrease, which may due to the alkalinity of HAP. Thischaracter has a bad effect on the char formation of IFR, which lower the efficiency of IFR.Futhermore, TG data indicate that HAP improved the thermal stability of PP/IFR composites;2) PZS was prepared and its chemical structure and morphology was measured by FTIR,fluorescence spectrum, and SEM. Then IFR was incorporated in it and used to ehance the flameretadancy of PP. Turns out that char’s ability to isolating heat and char’s compactness wereimproved by PZS, respectively. When PP was added with0.5wt%HAP and24.5wt%IFR, theLOI value of PP composites is31.1%and the composite can pass UL-94V-0grade. However, when the content of PZS increases, the flame retardancy of PP decreases, which means thatthere is little synergism between PZS and IFR.3) Based on the result of PP/IFR/PZS composites, PZS-g-PMo was synthesized and itschemical structure and morphology was measured by FTIR, fluorescence spectrum, and SEM.Then it was used to improve the flame retardancy of PP by combined with IFR. The resultshows that PP composites obtained the best flame retardancy when the mass content of PZS-g-PMo and IFR are0.5%and19.5%, respectively. The composite has the highest LOI value(31.5%), achieve UL-94V-1grade and has the best thermal stability, which is proved by TGdata. The flame retardancy of PP composites step down when the content of PZS-g-PMoincreases. However, the residue char increases as the content of PZS-g-PMo increase, whichindicates that the heat resisting property of its char is better. All results show that a goodsynergism between PZS-g-PMo and IFR exist and PZS-g-PMo is a promising synergisticcharing catalyst for IFR.