Modification of Cellulose Nanocrystals by Alkyl Acids with Different Chain Lengths
The study is aimed to investigate the effects of alkyl acids with different chain length on the hydrophobicity and thermal properties of cellulose nanocrystals(CNCs).Two alkyl acids with different chain length,acetic acid and stearic acid,were used to modify CNCs by esterification,with two modified products,acetylated cellulose nanocrystals(ANC)and stearic acid modified cellulose nanocrystals(MNC)obtained.Their hydrophobicity and thermal properties were tested and characterized.The results are as follows.The water contact angle was increased from 28.702°(CNC)to 62.606°(ANC)and 64.918°(MNC),respectively and the hydrophobicity of the modified products was all improved.However,due to the presence of acetyl groups,the thermal stability of ANC was increased by 47 ℃.Because long-chain alkyl molecules tend to break at high temperatures,the maximum thermal decomposition temperature of MNC was 34 ℃ lower than that of CNC,and its thermal stability was reduced.It is concluded that acetic acid,as a short-chain alkyl acid,can improve the hydrophobicity and thermal stability of cellulose nanocrystals to a certain extent.These results can provide a theoretical basis for the preparation of reinforced nanocomposites with hydrophobic polymers such as poly(lactic acid)in terms of properties.
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