Preparation and Application of Lignin Grafted Natural Rubber Initiated by CaCl2/H2O2
Adding compatibilizers is one of the effective ways to improve the poor compatibility between polar lignin(LN)and non-polar rubber,which helps to improve the reinforcing effect of LN.Herein,LN grafted natural rubber(LGN)was prepared using CaCl2/H2O2 as the radical initiating system,which acted as the compatibilizer for the natural rubber(NR)/LN composites.Detailed researches show that CaCl2/H2O2 can not only initiate LN to produce macromolecular free radicals,but also oxidize the double bonds of NR into unsaturated ketones which reduces the molecular weight of NR.Adjusting the feeding order in the grafting process and using CaCl2/H2O2 to treat LN first are helpful to reduce the oxidative degradation of NR and produce more LN macromolecular free radicals.The mechanism of LN grafted NR was explored by the Fourier transform infrared spectroscopy(FTIR)characterization of LN,NR and LGN,that is,the phenol hydroxyl radicals of LN reacted with the methyl groups of NR to form C—O—C bond.Benefiting from the excellent interfacial compatibilization of LGN,the tensile strength and tear strength of NR/LN composite after compatibilization increased by 14.3％and 7.5％,respectively,compared to those before compatibilization.This work provides a new way for preparing the compatibilizer of NR/LN composite,which is of great significance to promote the application of LN in the rubber industry.
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