纳米微晶纤维素-玉米淀粉复合氧化过程参数对其复合成膜液流变特性的影响

用纳米微晶纤维素(cellulose nanocrystals,CNC)与吸水润胀的玉米淀粉进行插层复配形成"CNC-淀粉"复合材料,采用NaClO对复合材料进行了氧化,并利用氧化玉米淀粉与聚乙烯醇(polyvinyl alcohol,PVA)/甘油(glycerol,GL)组合制备复合成膜液,探究了玉米淀粉浓度(3.0%、5.0%、8.0%和10.0%)、氧化及成膜液组分( PVA浓度为30.0%、40.0%、50.0% 、60.0%、70.0%和80.0%)对复合成膜液流变特性的影响。结果表明:氧化可导致玉米淀粉糊的黏度降低,且最低值为0.08 Pa·s;增加氧化玉米淀粉浓度可提高氧化玉米淀粉糊和复合成膜液的黏度、剪切应力、触变性和黏弹性,但稳定性降低,其中浓度为5.0%时,黏度较高,稳定性最好;增加PVA用量可提高成膜液黏度、剪切应力和黏弹性,PVA浓度为60.0%时,成膜液的黏度达最大值为9.9 Pa·s,黏弹性最高。玉米淀粉糊和复合成膜液均属于剪切稀释型非牛顿流体,表现出正触变性,流变特性符合Ostwald-de-Waele流体模型。

Effect of the Process Parameters of CNC-Corn Starch Composite Oxidation on the Rheological Properties of Its Composite Film-Forming Solution

In this paper, corn starch was oxidized by NaClO with the assistance of cellulose nanocrystals, and then mixed with polyvinyl alcohol and glycerol to prepare film-forming solution. The effect of corn starch concentration (3.0%, 5.0%, 8.0% and 10.0%), oxidation and film-forming liquid components (PVA 30.0%, 40.0%, 50.0%, 60.0%, 70.0% and 80.0%) on the rheological properties of the composite forming solution were investigated. The results indicated that oxidation could lead the reduction of viscosity, and the lowest was 0.08 Pa·s.The increase of oxidized starch concentration could improve viscosity, shear stress, thixotropy and viscoelasticity of the oxidized starch paste and the film-forming solution, however, its stability was lowered. The viscosity and stability of the oxidized starch paste and the film forming solution were good at 5.0% of the oxidized starch concentration. The increase of PVA dosage could improve viscosity, shear stress and viscoelasticity of the film-forming solution. the viscosity and viscoelasticity of film-forming solution reached maximum at 60.0% of PVA dosage, and the maximum viscosity was 9.9 Pa·s.Starch paste and film-forming solution showed shear-thinning property and positive thixotropy, and their rheological features could be fitted by Ostwald-de-Waele model.