Catalytic Effects of Nickel (Cobalt or Zinc) Acetates on Thermal and Flammability Properties of Polypropylene-Modified Lignin Composites

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• 作者：Youming Yu ; Ping鈥檃n Song ; Chunde Jin ; Shenyuan Fu ; Liping Zhao ; Qiang Wu ; Jiewang Ye
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2012
• 出版时间：September 26, 2012
• 年：2012
• 卷：51
• 期：38
• 页码：12367-12374
• 全文大小：606K
• 年卷期：v.51,no.38(September 26, 2012)
• ISSN：1520-5045

文摘

Previous work has demonstrated that functionalized lignin (PN-lignin) was shown to enhance thermal stability and flame retardancy of polypropylene (PP). To further strength these effects, nickel (cobalt or zinc) acetates were introduced into PP/PN-lignin systems in the present work. Thermogravimetric analysis demonstrates that adding 2 wt % nickel acetate (Ni(Ac)₂) catalytically degrades PP/PN-lignin but significantly increases the char residues in both N₂ and air conditions. For instance, the presence of Ni²⁺ reduced the initial degradation temperature (T_i) by 13 掳C but doubled the char residue in the N₂ condition relative to those of PP/PN-lignin. In comparison, the addition of cobalt or zinc acetate has little effect on thermal properties and char residues of PP/PN-lignin. Cone calorimeter results indicate that although the presence of Ni(Ac)₂ shortens slightly the time to ignition (t_ign) from 38 s to 31 s, it reduces the peak heat release rate (PHRR) from 380 kW/m² to 330 kW/m², suggesting a further improved flame retardancy of PP/PN-lignin. Moreover, the addition of Ni(Ac)₂ significantly increases char residue by 44%. Limited oxygen index (LOI) measurements show that adding Ni(Ac)₂ increases the LOI value from 22 for PP/PN-lignin (17.5 for pure PP) up to 26, also indicating a better flame retardancy. Unlike Ni(Ac)₂, cobalt or zinc acetate still has no obvious effect on flame retardancy. Char residue analysis shows that not only does Ni(Ac)₂ participate in the char-forming process of PN-lignin by itself but its degradation products, NiO and Ni(0), also promote the carbonization through the catalytic action of the PP matrix, both of which are primarily responsible for the enhanced flame retardancy of the PP/PN-lignin system.