用ATR分析工业润滑脂的变质

润滑油，如油和油脂，用于减少轴承和齿轮等机械元件之间的摩擦。随着时间的推移，润滑剂的效率会因氧化、蒸发或磨损碎屑而降低。建议定期对润滑剂进行质量检查，以安排预防性维护。此策略实现了高性能，最大限度地减少了停机时间和收入损失。ASTM方法包括在传输模式下使用FTIR来监测机械中的润滑剂。然而，这种方法有一些缺点，包括：（1）正确的样品体积和（2）难以测量高粘性样品，如油脂。为了解决这些问题，JASCO提供了一种使用衰减全反射红外光谱（ATR）的润滑剂评估方法；这是一种用于测量与高折射率棱镜接触的样品的技术。因此，该方法可以在最少的样品制备或预处理的情况下提供微体积测量。此外，表面测量的穿透深度取决于两个条件：（1）红外光的入射角和（2）棱镜和样品的折射率。ATR提供定性和定量信息。本应用说明显示了各种润滑脂样品（使用前后）的ATR测量结果，评估了水分、氧化和油分离。使用含有尿素基增稠剂的工业润滑脂作为样品。根据本应用中实验得出结论：该报告表明，ATR采样可用于快速有效地评估润滑剂性能，监测使用前后的水分进入、氧化影响和油分离。Application Note050AT0246 2/3Analysis of the Deterioration ofIndustrial Grease using ATRApplication Note Analysis of the Deterioration of Industria l Grease using ATR I ntro d uction Lubricants， such as o i l and grease are used to reduce f r ictio n between mechanical e l ements like bear in g and gears. Over t ime ， t h e e ffi c i ency of l u br i ca n t degrades d u e to oxidat i on，evaporatio n o r wear debr i s . Periodical qual i ty inspection of l ubr i cant i s recommended to schedu l e prevent i ve maintenance. This strategy enables hi gh pe r fo r mance， m i n i m izing down time an d los s of r ev e nue. Th e AS T M me th ods i nclu d e t h e use of FTIR i n tr a nsmis s ion mode t o mo n itor lu b r i c a nts i n mac h ine r y. However， t hi s method has some disadvantages including ： (1) correct sample volume and (2) di f f i cu l ty measur i ng highly viscous samp l es such as grease. Figure 1. ATR PRO ONE In order to address t h ese issues， J ASCO offe r s a lubr i cant evaluat i on method using FTIR wi t h attenua t ed total r eflectance (ATR)； which i s a tec h niq u e for measur in g samples in contact wit h a high ref r active index p rism . Therefore， th i s m ethod can offer micro-volume m e as ur ement with minimal sample pre p aration o r pretreatmen t. In addi t ion， t h e penetration depth of su r face meas u remen t depends on two condi t ions： (1) i ncident angle of i n fra r ed l i ght and (2) refractive indic e s of prism a n d sample. ATR provi d es b ot h q u a lit a t i v e a n d q u an t i tat i v e informat i on. Measurement I n st r um ents F T/I R -4600R e so l u ti o n 4c m ²M et h od AT R D e te cto r DLA TGS A cc umu l at i on This application note shows result of ATR measu r ements o f various grease samp l es (before a n d after use)， evaluating moisture ， oxidat i on and oil -separa ti on .Industrial grease contai ni ng urea -b a s ed thickene r was u sed as a s a mple. 16 ti m e s (A p p rox. 20 s e c) A cc es sor y A T R P R O O N E (Fi g. 1) P r is m Di amond K eywords ATR， g r ease， oxidat i on， moisture， oil-sepa r at i on ，lubricant Resu l t Moisture Evaluation F i gure 2 Spectra of t h e O-H reg i on， showing a d i f f erence in t he spect r a of the grease b efore and after u se . The broad absorption peak att rib uted to O-H stretch i ng vi b rat i on (3500-3000 cm-1) indicates water p enetratio n in the lu b r i cant. One can also evaluate t h e t endency of moisture absorpt i on i n the g r ease samp l e qua n titative l y. This requires the creat i on of a calibratio n curve using standards wit h k nown concentra ti ons. JASCO's Spectra Manage r" software can be used with c l ass i cal l e ast squares (CLS) cali b rat i ons as well as ot h er c h emome t ric techniques. Figure 2. Spectra of grease (O-H reg i o n ) Oxidation Evaluation Grease generally consists of a base oi l， thickener， and additives. I f t h e base oil oxidizes， carbonyl and alde h yde are g e n e rated. An i n crease and/or decrease of t h e absorption p eak att ri bu t ed to the C =0 st r etc h i n g vibratio n (n ear 1720 cm-1) can be i n terpreted as ox i dation of t h e b ase oil . Figure 3 shows a distinct di f fere n ce in th e C=O regio n of grease b efore and afte r use. I n addit i on ， plotting the peak height o r area al l ows the oxidat i o n to be estimated quantitat i vely. Figure 3. Spec t ra of gre a se (C-O regi on ) Figure 4. S p ectra of greas e (C-H r egio n ) Oil-Separation Evaluation With the moveme n t of mechanic a l parts， t h e base oi l is separated from t he grease. T his decreases the perform a nce of the lubricant. FTIR spectroscopy can be used to evaluate this separatio n u si n g the following formu l a： A mi de C = 0 p eak (1630 cm1) of the ure a-b a s e d thi c k e n e r A r ea Rat i o =C -H p e ak (ar ou n d 2900 cm1) of b a se oil a n d t h icke n er The calculated result of the grease before use was 28.9， and the result after use was 16.3. These show that t he base oil was sign ifi can tl y sepa r ated from t h e greas e . JASCO prov i d e s FTIR measur e men t usi n g S p ect r a Manager t o simpl i fy the above e valuation met h od s and offers a 'tu r n-key' so l utio n to t h e analyst . Conc l u s ion Thi s r e por t demonst r at e s that ATR sam p ling can b e u s ed to e valuate l u b r i cant per f ormance q u ickly a n d eff e c ti v el y，monitoring the i n g r ess of moisture， effects of ox i dation， and oil separatio n before and after use.