机械活化干法制备新型淀粉基水泥砂浆保水增稠剂

Preparation for Novel Starch-Based Water-retention and Thickening Admixture of Cement Mortar by Mechanical Activation-strengthened Dry Method

以木薯淀粉为原料,氯乙酸钠为醚化剂,三偏磷酸钠为交联剂,采用机械活化干法制备交联羧甲基淀粉保水剂。以取代度(the degree of substitution,DS)和黏度为评价指标,通过单因素和正交试验设计优化确定最佳制备工艺,采用红外光谱(fourier transform infrared spectroscopy,FTIR)、X-射线衍射(x-ray diffraction,XRD)、扫描电镜(scanning electron microscope,SEM)对交联羧甲基淀粉的结构进行表征,并考察不同添加量的交联羧甲基淀粉对水泥砂浆性能的影响。结果表明,交联羧甲基淀粉保水剂的最佳工艺参数为:淀粉与氯乙酸钠摩尔比为1∶0. 85、淀粉与氢氧化钠摩尔比为1∶1、淀粉质量1%的三偏磷酸钠、球磨温度50℃、球磨时间60 min,在此条件下制备的交联羧甲基淀粉取代度为0. 8373,黏度为3493 mPa·s。FTIR、XRD、SEM进一步证实木薯淀粉发生了交联羧甲基化反应。将0. 5%的交联羧甲基木薯淀粉添加到水泥砂浆中,砂浆的保水率从77. 1%提高到98. 2%,凝结时间由246 min延长至282 min,稠度值由57 mm减小至36 mm。微观测试表明,添加淀粉基保水剂的砂浆硬化体中方解石晶体减少,砂浆结构更加紧密。

By using cassava starch as raw materials, monochloroacetate as etherifying agent and sodium trimetaphosphate as cross-linking catalyst, the cross-linked carboxymethyl cassava starch was synthesized by mechanical activation-strengthened dry method. Single factor experiments and orthogonal array design methods were used to optimize the preparation conditions based on the degree of substitution (DS) and the viscosity. The structure of the cross-linked carboxymethyl cassava starch were characterized by using fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM). The cross-linked carboxymethyl cassava starch was then applied to cement mortar. The optimal process parameters were obtained as follows: the mole ratio of starch and sodium chloracetate was 1∶ 0.85. The mole ratio of starch and sodium hydroxide was 1∶ 1. The sodium trimetaphosphate of the starch weight was 1%, ball-milling temperature was 50 ℃. Ball-milling time was 60 min. The degree of substitution of products was 0.8373. And the viscosity of products was 3493 mPa·s. The cross-linking and etherification reaction of cassava starch have been further confirmed by FTIR, XRD, SEM. By adding the 0.5% of cross-linked carboxymethyl cassava starch to the cement mortar, the water-retention rate of the cement mortar increased from 77.1% to 98.2%, the setting time prolonged from 246 min to 282 min, and the consistency decreased from 57 mm to 36 mm. Microscopic test showed that the calcite crystal of cement mortar mixed with appropriate cross-linked carboxymethyl cassava starch was decreased, and the cementitious materials exhibited more intensive structure.