Preparation and properties of cellulose isocyanate based lubricating grease
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摘要: 随着石化资源的日益枯竭以及人们环保意识的提高,润滑脂的绿色可持续发展迫在眉睫。本文以天然可再生的微晶纤维素为原料,对其进行表面异氰酸酯化改性进而制备了环保型纤维素基润滑脂。采用FTIR、SEM、XRD以及TG等手段分析了纤维素表面的接枝效果。利用流变仪和四球摩擦试验机系统研究了纤维素基润滑脂的流变特性和摩擦学性能。研究结果表明:纤维素经过异氰酸酯改性后,极大地提高了其对基础油的增稠能力。相较于纯纤维素基润滑脂,改性纤维素基润滑脂的抗剪切能力得到了提升,临界点和流动点显著增加。并且,两种润滑脂表现出相似的粘弹性规律,在0~50 ℃范围内,线性粘弹性函数随温度升高而下降;在50~100 ℃范围内,线性粘弹性函数则随温度升高而升高。改性纤维素基润滑脂的抗磨性有所提高,磨斑直径从0.873 mm下降到0.820 mm。该工作为环保型润滑脂的制备提供了创新思路。Abstract: With the increasing depletion of petrochemical resources and the improvement of people's awareness of environmental protection, the green and sustainable development of grease is extremely urgent. In this study, environmental-friendly cellulose-based lubricating grease was prepared by surface isocyanate modification using natural and renewable microcrystalline cellulose as raw material. The grafting effect on the surface of cellulose was analyzed using FTIR, SEM, XRD, and TG methods. The rheological and tribological properties of cellulose based lubricating grease were studied using a rheometer and a four ball tribotester. The research results indicate that after modification with isocyanate, cellulose greatly improves its thickening ability on base oil. Compared to pure cellulose-based grease, the shear resistance of modified cellulose-based grease has been improved, and the critical point and flow point are significantly increased. Moreover, the two types of lubricating greases exhibit similar viscoelastic laws, with a linear viscoelastic function decreasing with increasing temperature in the range of 0-50 ℃; In the range of 50-100 ℃, the linear viscoelastic function increases with increasing temperature. The wear resistance of modified cellulose-based grease has been improved, and the wear spot diameter has decreased from 0.873 mm to 0.820 mm.
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Key words:
- lubricating greases /
- cellulose /
- isocyanation /
- rheological properties /
- tribology
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表 1 MDI、MCC、MCC-MDI以及润滑脂的TGA数据
Table 1. TGA characteristic parameters for the MDI、MCC、MCC-MDI and lubricating grease
Samples T5% /℃ Tmax /℃ Yc /% MDI 169.0 262.5 1.8 MCC 271.2 350.7 4.3 MCC-MDI 290.1 347.7/373.0 14.3 MCC/O 296.1 352.8/424.8 2.3 MCC-MD/O 298.7 369.5/424.5 3.3 Notes: T5%-Onset degradation temperature; Tmax-Maximum decomposition; Yc-Char yield at 800 oC 表 2 MCC/O、MCC-MDI/O以及MCC-MDI-ODA/O的摩擦学性能表
Table 2. Friction performance of MCC/O, MCC-MDI/O and MCC-MDI-ODA/O
Samples Friction coefficient Friction force/N Wear scar diameter/mm MCC/O 0.077 3.783 0.873±0.075 MCC-MDI/O 0.113 5.542 0.820±0.062 MCC-MDI-ODA/O 0.085 4.169 0.455±0.037 表 3 与其他生物质基润滑脂的摩擦学性能对比
Table 3. Comparison of friction performance with other bio-based lubricants
Thickener type Friction coefficient Ref. Montmorillonite/cellulose 0.095 [21] Cellulose pulp 0.086 [22] Ethylcellulose nanofibrous 0.075 [23] Barley straws 0.092 [24] Wheat straws 0.095 [24] Epoxidized lignocellulosic 0.12 [25] Eucalyptus lignin/cellulose acetate 0.092 [26] Poplar lignin/cellulose acetate 0.076 [26] Olive lignin/cellulose acetate 0.070 [26] Kraft lignin/cellulose acetate 0.067 [27] Kraft lignin/ethylcellulose 0.088 [28] Alkylated lignin 0.097 [29] NCO-functionalized lignin 0.083~0.089 [30] Acylated chitosan 0.12 [31] MCC-MDI 0.085 This work -
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