低温下生物柴油的胶凝特性研究

利用流变仪在小振幅振荡剪切模式下对地沟油、花生油和大豆油生物柴油的胶凝特性进行了研究。结果表明,低温下生物柴油不仅具有冷却胶凝特性,还表现出明显的等温胶凝特性。分析了冷却速率和剪应力对地沟油生物柴油胶凝特性的影响。结果表明,静态降温时降温速率越大,生物柴油的胶凝温度越低,降温及恒温静置过程中同一温度下的胶凝结构越弱。相同降温速率下,生物柴油的胶凝结构和胶凝温度随剪应力的增加而降低,但经受不同剪应力作用的生物柴油恒温静置后胶凝结构相差不大。降温过程中施加的剪应力较小时,冷却胶凝结构随降温速率的增大而降低;剪应力较大时,冷却胶凝结构随降温速率的增大而加强。不管施加的剪应力多大,等温胶凝结构随降温速率的增大而加强。

Gelling properties of biodiesel at low temperatures

The gelling properties of biodiesels were studied with rheometer in the modes of small amplitude oscillatory shearing. The results show that in addition to the cooling gelling properties, biodiesels also show obvious isothermal gelling properties at low temperatures. The effects of cooling rate and shear stress on the gelling properties of biodiesels were studied. The gel point of biodiesel decreases and the strengths of gel structure at the same temperature during cooling and isothermal gelling process weaken with the increase of cooling rate under quiescent conditions. At the same cooling rate, the gel strength during cooling and isothermal gelling process is much weaker with increasing shearing stress. However, the gel strength of biodiesel has little difference after isothermal gelling process although the shear stress applied during cooling process is different. During cooling the gel strength decreases with the increase of cooling rate when the applied shear stress is smaller; but the gel strength increases with the increase of cooling rate when the applied shear stress is larger. No matter the shear stress' values applied in cooling process, the gel structure is enhanced with the increase of cooling rate during the isothermal gelling process.