Design For Esterification Of Hydrogenated Hydroxyl-terminated Polybutadiene As A Lubrication Oil And Performance Study

Liquid lubricant is one kind of the most important materials that decreased friction and wear of the tribo-pairs,and prolonged the life of the mechanical equipment.As the industry technology rapidly developed in recent years,the mechanical components need longer operating life and more demanding operating conditions.Higher performance liquid lubricants should be developed to meet the requirement of the mechanical equipment that worked in severe conditions,and to reduce the costs of the equipment maintenance.Poly-α-olefins(PAOs)and synthetic esters are the most widely used base oil.PAOs have the advantages of good chemical stability,high viscosity index,and excellent low-temperature performance.Both of them are widely used in the automobile industry and machinery industry.But the polarity of PAOs molecule is weak,which leads to its poor compatibility with polar additives.Synthetic esters have excellent compatibility with most additives.Addeitionally,they also possess the advantages of excellent lubricating property,load capacity and good low-temperature performance.But several properties such as the hydrolytic stability,thermal stability and corrosion resistance are unsatisfactory.Otherwise,some of the synthetic esters also have high volatilization loss.Hydrogenated hydroxyl-terminated polybutadiene(HHTPB)is a kind of telechelic low molecular weight liquid perpolymer developed in the 1960s.Part of the HHTPB molecular chain structure is same as the PAOs molecular chain.HHTPB could be functional by the reaction of hydroxyl of the HHTPB with carboxyl,Si-O-R et al,so as to perparing liquid lubricant with excellent performance.In this thesis,a series of esterification of HHTPB(EHHTPB)were designed and prepared.The modified methods of additives using in EHHTPB were investigated.The rheological and tribological properties were measured.Additionally,the lubrication mechanisms of the additives using in EHHTPB were also explored.The main results are shown as follows:(1)A series of EHHTPB with different molecule structures were prepared by the condensation reaction of HHTPB with linear C2-C12 alkyl-chain fatty acids and fatty acids with side groups.The viscosity of the series of EHHTPB were lower than the viscosity of HHTPB,except the HHTPB based neodecanoate(ND-HHTPB-ND).In addition,the viscosity increased with the increasing chain length and number of side groups.EHHTPB showed excellent lubricating property benefiting from the lower viscostity and the higher wetting rate on rubbing surface than HHTPB at high speed.EHHTPB with side groups were more effective in reducing worn at high load conditions owing to higher oil film thickness.The EHHTPB had high molecule weight and eater groups,so it displayed low volatilization loss,high viscosity index and excellent thermal stability.Compared with two kinds of PAOs base oil with similar viscosity,the diameter of the ball lubricanted with HHTPB based octanoate was reduced by 71%at heavy load conditions.It is expected to solve the lubrication problem of machinery worked at high load.(2)Large size graphene oxide sheets modified with dodecylamine(DA-GO_L)and small size graphene oxide sheets modified with dodecylamine(DA-GO_S)as additives showed excellent dispersion in O-HHTPB-O.But the dispersion of chemical reduced large size graphene oxide sheets modified with dodecylamine(DA-r GO_L)was a little worse.The viscosity of the oil increased with the content of DA-GO_Land DA-r GO_Lincreasing.DA-GO_Senhanced the lubricating and wear resistance performance of the O-HHTPB-O most significantly among the three additives,however,DA-r GO_Limproved the poorest.DA-GO_S/O-HHTPB-O became thinner as the DA-GO_Scontent increased because of the small size of DA-GO_S.So that the DA-GO_S/O-HHTPB-O oil could wet the rubbing surface more quickly.At light load and high speed conditions,the diameter of the worn scar decreased by 37%,when the content of DA-GO_Sreaches more than 0.10wt%.Under heavy load,the lubricating and anti-wear properties of DA-GO_Swere excellent even at low content.DA-GO_Swere easy to embedding into the rubbing surface and formed friction films to reduced friction and wear.DA-GO_Land DA-r GO_Lreduced wear just under high load conditions.When the DA-GO_Lcontent is 0.03wt%,the diameter of the wear scar can be reduced by 31%.The size of the DA-GO_Lsheets in O-HHTPB-O after the tribological test decreased significantly.A large number of the C-N bonds andΠ-Πstructures in DA-GO_Lsheets were destroyed and oxidized during friction.(3)Large size GO(O-HHTPB-GO_L)/O-HHTPB-O and small size GO(O-HHTPB-GO_S)/O-HHTPB-O were prepared via the different sizes of GO sheets condensing with octanic acid and HHTPB in-situ.The viscosity of O-HHTPB-GO_L/O-HHTPB-O and O-HHTPB-GO_S/O-HHTPB-O increased with the content of GO increased.But the viscosity of O-HHTPB-GO_S/O-HHTPB-O was lower than the viscosity of O-HHTPB-O.O-HHTPB-GO_Lenhanced anti-wear significantly under high load condition.O-HHTPB-GO_Sshowed good lubricating and anti-wear effects under both light load and heavy load.At light load and high speed conditions,the diameter was reduced by66%when the content of O-HHTPB-GO_Sis 0.03wt%.Under heavy load and high speed,the friction coefficient was reduced by 13%,and the diameter was reduced by20%when the content was 0.06wt%.O-HHTPB-GO_Sinduced wear is more significant than O-HHTPB-GO_Land DA-GO_S,owing to the excellent thermal stability,mending effect and the favorable flowability.(4)Carbonquantumdotsmodifiedwithdodecylamine(DA-CQDs)/O-HHTPB-O were successfully prepared.And CQDs were condensed with octanic acid and HHTPB in-situ to prepare O-HHTPB-CQDs/O-HHTPB-O.The viscosity of DA-CQDs/O-HHTPB-O decreased with the content of DA-CQDs increased.However,the viscosity of O-HHTPB-CQDs/O-HHTPB-O increased as the content of O-HHTPB-CQDs increased.Under heavy load and low speed,the lubricating and wear resistance properties of DA-CQDs were better than O-HHTPB-CQDs.When the amount of DA-CQDs was0.03wt%,the friction coefficient and the diameter of worn scar could be reduced by23%.The friction and wear reduction effects of O-HHTPB-CQDs at high speed were more excellent than that of DA-CQDs and O-HHTPB-GO_S.Under light load and high speed,O-HHTPB-CQDs played a rolling effect owting to the suitable size and viscosity.Under heavy load and high speed,when the amount of O-HHTPB-CQDs is0.10wt%,the friction coefficient decreased by 31%and the diameter decreased by23%.DA-CQDs and O-HHTPB-CQDs both showed a mending effect,rolling effect,and forming friction films on the rubbing surface under specific conditions.