1 Introduction
The
color
darkening process of lubrication oils has been making sense of consumers
and researchers out of confusion when makes decisions that the
deteriorated oils should be replaced. Especially in the application of
aviation lubrication oils, there is very limited room for the inaccurate
assessment of the oil quality due to the strict flying safety standards.
Many researches of the oils color number have established many
interesting assessment standards about our
daily
life1-4. In industrial field, the color index of
transformer insulating oil has been considering the very critical in
ensuring the safety as well as optimal performance of the
equipment5. The color of oils could also lead to some
important application6 which is vital towards our
living environment.
To be the important component of effective lubrication system, the
aviation lubrication oil is facing the challenge of color change which
is usually related to the quality deterioration of the oils.
Colorimeter
has a long history for measuring the quality of the refined petroleum
products since 19337-9, which also suggests the color
is an important parameter of aviation lubrication oils. As reported by
the previous study10-12, the molecular structure
change and the properties deterioration of the oxidized oil samples are
confirmed, which also result in gradually changing of the oxidized oil
samples color. However, the intrinsic relationship between the oil
molecules (oxidizing products and antioxidants) and the resulting color
variation needs to be established which could develop a fast and
low-cost strategy to rapidly estimate the oil quality.
On the other hand, the gas chromatography mass spectroscopy (GCMS) is
powerful method to be widely applied to determine from the molecular
structures13 and degradation
reactions14, 15 to oil quality16 of
the lubrication oils. Based on the conjoint analysis of GCMS and color
number, the key performances of the oxidized oil samples including fully
formulated aviation lubrication oils and base oils are measured to study
the relationship between the color, molecular structure and performances
of the oxidized oil samples. Towards a fully formulated aviation
lubrication oil, the color number could be an easy-acquired oil quality
signal to fast evaluate the residual life of the in-service oil after
the relationship between the color, molecular structure and performances
of the oxidized oil has been established.