The effect of preparation and characterisation

The effect of preparation and characterisation of polyurea grease

X.Z.Dai1,P.Guo1,D.M.Hong1,J.D.Hui2,Z.M.Hui2and F.Geng*1,2,3

There are many factors that affect the performance of polyurea grease,such as gelatiniser,base oil, additives,material production process and the formulations.In this study,the preparation of polyurea grease is mainly investigated by changing the production process,which include the refining temperature,the mode of adding of cooling oil,the cooling methods and the frequency of grinding.Meanwhile,the kinds of base oil are also studied.The characteristics of cone penetration,steel net oil,extreme pressure and antiwear properties,water resistance,etc.were studied.The prepared polyurea grease shows a high dropping point,good water resistance, corrosion resistance and very high extreme pressure and antiwear properties.

Keywords:Polyurea grease,Production,Refining temperature,Grinding,Lubricating additives,Tribological properties

Introduction

Polyurea grease has attracted a lot of attention thanks to its ideal comprehensive performance,such as high drop-ping point,mechanical shear stability,rust resistance, anti-settling,water resistance,etc.Especially for its own outstanding oxidation stability,thermal stability and long lifetime,it can be widely applied in areas of steel industry,automobile industry,electrical equipment, defense industry,etc.Nowadays,it has become a develop-ment direction of high-performance grease species in the world.With the rapid development of the bearing indus-try,a good antiwear property as an imperative role was required to reduce the power of the device driver,save energy and improve lifetime.1

Polyurea grease is prepared by reacting isocyanate and organic amine to give a gelatiniser,then thickened using mineral oil or synthetic oil.Nowadays,there are many research reports on the development,preparation,charac-terisation and application of polyurea grease.Had et al.2,3 reported the factors affecting the development and per-formance of polyurea grease.Xu et al.4researched the effect of post-treatment process on the performance of polyurea grease.Sun et al.researched the industrial appli-cations and the basic theory including the development of polyurea grease,performance of the additives,their struc-ture and reaction mechanisms.5–8Zong9and Deng et al.10 also researched the composition of polyurea grease.Bao et al.11researched the magnetic urea grease.There are a lot of research reports on polyurea grease.However, there is a wide variety of isocyanates and organic amines to choose from.Different types of isocyanates reacting with different organic amines could show different gelati-niser structures and different performances.To obtain the excellent performance of the polyurea grease,optimum model of isocyanates and organic amines must be selected. Moreover,it is necessary to optimise the types of base oil and additives.In addition,the preparation technology also has a significant impact on the performance of urea-based grease,such as elevated temperature,keeping temperature,cooling and change in maximum refining temperature,cooling mode,grinding manner and fre-quency,etc.Therefore,the production process conditions have an important significance for the study of polyurea grease,commercialisation and industry applications.

In this study,the effect of base oil and preparation con-ditions including grinding mode,refining time,cooling types,etc.on the polyurea grease performance are dis-cussed in more detail.The prepared polyurea grease shows excellent performance by optimising the compo-sition and process conditions.

Experimental

Materials

Petroleum ether with AR colourless liquid and polyurea gelatinise powder are produced by Jiangsu Qiangsheng Chemical Co.,Ltd.The500SN mineral oil,150BS oil, PAO40,silicone oil and ester oil were purchased from SK chemical Co.,Ltd(Tianjin,China).

Instruments

Electronic precision balance(LAC214)and grease wide temperature drop point tester(SPH3498)produced by Changzhou Wantai Precision Balance Co.,Ltd,were used.Powerful electric mixer(JB90-D)produced by Shanghai Hengqin Instrument Co.,Ltd,was used. Grease cone penetration tester(TDGC2)produced by JinShanmen Instrument Co.,Ltd,was used.

1Department of Chemistry and Materials Engineering,Changshu Institute

of Technology,Changshu,Jiangsu215500,China

2Suzhou Huifeng Lubricant Co.,Ltd,Heshi Industrial Park,Zhitang Town,

Changshu,Jiangsu215538,China

3School of Materials Science&Engineering,Jiangsu University,Zhenjiang,

Jiangsu212013,China

*Corresponding author,email gengfei8287@https://www.wendangku.net/doc/f72482058.html,

?W.S.Maney&Son Ltd2015

Received20October2014;accepted18December2014

DOI10.1179/1432891714Z.0000000001158Materials Research Innovations2015VOL19SUPPL5 S5-588

Thermostatic drum wind drying oven(DDF-1·5KW) produced by Kunshan Xinjiulong Instrument Co.,Ltd, was used.Grease water resistance tester(SPH269)and grease four-ball tester produced by Shanghai Puhang Petrol Instrument Co.,Ltd,were used.

General procedure

A measure of88·2g500solvent neutral(SN)mineral oil, 37·8g150Bright Stock(BS)oil and24g polyurea soap powder were added into the container,stirred and heated to70°C,maintained for30minutes,and then heated to150°C,maintained for2hours,and then heated to 170°C,maintained for1·5hours,and then heated to 190°C,maintained for15minutes.The system was cooled when the reaction is complete,and then grounded. Base oil was all added at once;no base oil was added in the process.Three cooling modes were chosen,including rapid cooling,standing cooling and stirring cooling. Results and discussion

The appearance of polyurea grease by different process conditions

The polyurea grease that is made by stirring,cooling and grinding twice is dark brown and semi-hard.The poly-urea grease that is made after a maximum temperature of170°for1hour with the same base oil is shallow brown,bright coloured,with some partially pointed. From Fig.1,we can see that the different base oil and different process reaction conditions,both make a big difference to the appearance of polyurea grease and cone penetration.

The influence of base oil on the performance of polyurea grease

Different base oils have different viscosities,so different polyurea greases were made.This experiment tests every performance by adding synthetic hydrocarbon oil, mixing mineral oil,silicone oil and mixing oil containing synthetic hydrocarbon oil and ester oil.The test data are shown in Table1.

The viscosity of synthetic hydrocarbon oils was higher. The polyurea grease made by synthetic hydrocarbon oils could not become greasy.Silicone oil does not react with thickener,and the result was bad.

The performance of polyurea grease that was made by PAO40mixed with ester oil and mixing mineral oil was great,so they were the good choice for base oil.Maximum processing time impact on the performance of polyurea grease

During the production of polyurea grease,refining temp-erature made a big difference to the structure of polyurea grease.The refining temperature of this experiment was 190°C.The refining times were15minutes and60 minutes,and the result is shown in Table2.

Maximum response time made some difference to the performance of polyurea grease.When the maximum response time becomes longer the polyurea grease and anti-water drenching becomes softer and worse,and the weld point(PD)and the maximum non-seizure load(PB) become smaller;steel oil became bigger than before.So, 190°C/15minutes should be chosen.

The influence of cooling oil on the performance of polyurea grease

There are two ways for adding cooling oil.The first way is adding all the oil in the beginning.The second way is adding the cooling oil while the temperature is going up.Those two ways made some difference to the perform-ance of polyurea grease.Table3gives the testing

data.

1The appearance of polyurea grease with different

production

Table2Test data of performance with different maximum

response times

Project

Reaction time

190°C/15

minutes

190°C/60

minutes

Cone

penetration/

0·1mm

Before34·4934·91

After40·8342·12

Cone

penetration

63·472·1

Anti-water drenching(38°C)(%)1·23·6

Steel oil(30hours)(%)0·0961·72

Drop point(°C)305305

Four-ball friction PB/N610520

PB/N16001260

Grinding spot/

mm

0·551·53

Wear lost0·0570·053

Average friction

coefficient

0·0960·091

190°C/15minutes means react15minutes in190°C.

Table1Test data of different base oils

Project

Species of base oil

Mixing

mineral oil

PAO

40+10%

ester oil

Cone

penetration/

0·1mm

Before34·4940·39

After40·8342·12

Cone

penetration

63·472·1

Anti-water drenching(38°C)(%)1·282·1

Steel oil(30hours)(%)0·0960·28

Drop point(°C)305304

Four-ball

friction

PB/N610710

PB/N16002000

Grinding spot/

mm

0·550·46

Wear lost0·0570·048

Average

friction

coefficient

0·0960·093

Mixing mineral oil consists of500SN and150BS by7:3.PAO:

ester oil is9:1.

Dai et al.The effect of preparation and characterisation of polyurea grease

Materials Research Innovations2015VOL19SUPPL5S5-589

So we can see that the way of adding cooling oil almost make no difference to the performance of polyurea grease.In addition to grinding spot,the others have no change.

The ways of cooling impact on the performance of polyurea grease

From Table 4,we can see the data of performance of using stirring cooling which is better than any other.Taking cost into account,too much time will be spend if we choose stirring cooling.So,we can choose static cool down for the common polyurea grease.But if there

are strict requirements to every performance,we found stirring cooling to be better.

The ways of grinding impact on the performance of polyurea grease

The duration of grinding make some difference to the per-formance of polyurea grease,if the time is too much,the polyurea grease will become softer,the bond could be blocked and the performance will get worse.However if the time is too little,polyurea grease will become hard and the cone penetration will not be up to the standard.So,a right grinding time will improve the performance of polyurea grease.The test data are shown in Table https://www.wendangku.net/doc/f72482058.html,pare with test after 1day,let polyurea grease stand 7days,it became harder,the cone penetration became bigger,the other performances all became worse.

Compare with test after 5days,grind once after 3days,the performance include anti-water drench and drop point became better,and performance was very stable.

Conclusion

If the viscosity of PAO40is very high,the performance of the polyurea grease that was made by PAO40is not good,so is silicone oil.The performance achieved the standard when made by mixing mineral oil.The polyurea grease was better when made by 90%synthetic hydrocarbon oil and 10%ester oil than mixing mineral oil.

The best maximum processing time was 15minutes.Extend the time the PD and PB will get smaller,anti-

Table 4Test data of different cooling modes Project

Cooling mode

Rapid cooling Static cool down Stirring cooling Cone penetration /0·1mm Before 36·3541·3934·49After

43·3248·240·83Cone penetration

69·768·163·4Anti-water drenching (38°C)(%)4·634·11·2Steel oil (30hours)(%)1·770·50·096Drop point (°C)292300305Four-ball friction

PB /N 560560610PB /N

126016001600Grinding spot /mm 0·61·560·55Wear lost

0·0620·0590·057Average friction coefficient

0·083

0·088

0·096

Table 3

Test data of the performance with two different ways of adding cooling oil

Project

Adding mode +?Cone penetration /0·1mm

Before 34·4925·51After

40·8331·77Cone penetration

63·463·4Anti-water drenching (38°C)(%)1·21·2Steel oil (30hours)(%)0·0961·21Drop point (°C)305302Four-ball friction PB /N

610610PB /N

16001660Grinding spot /mm 0·550·46Wear lost

0·0570·024Average friction coefficient

0·096

0·089

‘+’means add all oil at beginning,‘?’means add last 1/3base oil after 170°C.

Table 5Test data of different grinding ways Project

Cooling mode

2t*1d 2t*7d 2t*3d*1t 2t*3d 1t*1d 1t*3d*1t 1t*3d Cone penetration /0·1mm

Before 37·6436·8932·9341·440·7234·5338·68After

53·9642·6939·148·1747·0240·8345·64Cone penetration

63·25862·767·763·36369·6Anti-water drenching (38°C)(%)3·1422·942·913·053·013Steel oil (30hours)(%)0·390·010·30·370·390·310·3Drop point (°C)308304310304302305304Four-ball friction PB /N

560560610610560610610PB /N

160016001600160016001600600Grinding spot /mm 0·480·520·530·580·490·570·6Wear lost

0·050·0540·0550·060·520·0590·062Average friction coefficient

0·09

0·095

0·09

0·091

0·092

0·069

0·094

2t*1d means grind twice and test 1day later;2t*3d*1t means grind twice and test 3days later,and test again 7days later.

Dai et al.The effect of preparation and characterisation of polyurea grease

Materials Research Innovations 2015

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water drenching a steel oil will be more,but made no difference to the cone penetration and drop point. Changing the mode of addition of cooling oil has little influence on the performance of the polyurea grease.So, for convenience,base oil could be added in the beginning to save time.

Stirring cooling is the best way among the three cooling modes;maybe molecular structure will be distributed more evenly when stirring the polyurea grease.

The biggest problem of polyurea grease is that polyurea grease becomes hard after standing for a certain time,it will affect its use.It could improve the performance of the polyurea grease through changing grinding way and frequency.Grinding way have much influence on the per-formance of the polyurea grease,grinding three times is better than once and twice,especially grind the polyurea grease after3days and7days. Acknowledgements

The authors thank the financial support from the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(13KJB430002),National Natural Science Foundation of China(grant no.11405014),the Project Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry(SZ2013201)and China Postdoctoral Science Foundation(2013M541610).They also thank the Suzhou Huifeng Lubricant Co.,Ltd,for

the help with measurements.

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Dai et al.The effect of preparation and characterisation of polyurea grease Materials Research Innovations2015VOL19SUPPL5S5-591