Tribological Properties And Corrosion Resistance Of Polymer Composites Modified By Micro/Nanocapsules

Friction and wear have brought huge losses to human’s life.At present,more than 50%of the mechanical equipment accidents originated from lubrication failure and excessive wear.The development of self-lubricating materials is one of effective way to reduce friction and wear.Polymer composites are widely applied in friction-resistance materials due to their light weight,high mechanical properties,excellent environmental adaptability and workability,good chemical stability and anti-corrosion properties.The rapid development of high-tech equipment has put forward higher requirements for self-lubricating polymer composites.It is of great significance to study self-lubricating polymer composites with low friction,high load and long life to meet the application requirement under extreme working conditions.Microcapsules are one of the effective methods to improve the tribological properties of polymer composites.However,the main problem at present is that microcapsules are difficult to meet the application requirements of polymers requiring high temperature molding,which limits the application of microcapsules in friction materials requiring high temperature molding,such as PA,PEEK and PI et al.Therefore,this paper proposed to prepare the high-temperature resistance micro/nanocapsules and their PA6 self-lubricating composites.The tribological properties of PA6 self-lubricating composites were studies.In order to expand the application range of microcapsules,a kind of double functional epoxy coating with self-healing and self-lubricating functions was proposed,and its tribological properties and corrosion resistance were studied.（1）High-temperature resistance IL@SiO₂ nanocapsules were prepared by using ionic liquid as core materials and SiO₂ as wall materials.The effect of surfactant type on the properties of nanocapsules was discussed in one-step method（sol-gel method）.The experimental results showed that due to the high viscosity and bipolar properties of ionic liquid,neither CTAB nor F127 surfactant could be used to prepare the IL@SiO₂ nanocapsules successfully.When the SiO₂ Pickering dispersant was used as the surfactant,the average particle size of prepared IL@SiO₂ capsules was about 10μm and the core content was 22.8wt.%.It was difficult to control the size of the capsules to the nanometer scale.In the two-step method（sol-gel plus vacuum impregnation method）,PAO@SiO₂ nanocapsules were prepared by using polyalphaolefin（PAO）and CTAB as soft template.The influences of CTAB dosage and core wall ratio on the properties and core content of PAO@SiO₂nanocapsules were investigated.The template was removed by high-temperature roasting,and hollow mesoporous SiO₂ was prepared.Then,IL was loaded into SiO₂ by vacuum impregnation.High thermal stability IL@SiO₂ nanocapsules with core content of 47.7 wt.%and average particles size of410 nm were prepared successfully.（2）PA6 self-lubricating composites modified by IL@SiO₂ nanocapsules were prepared.The mechanical,dynamic thermomechanical and thermal properties of PA6 composites with different nanocapsules content were discussed.The addition of nanocapsules had little effect on the tensile strength and bending strength of the PA6 composites,but can reduce the break elongation and increase the elastic modulus.The nanocapsules had no obvious effect on the glass transition temperature of the PA6 composites.The crystallization temperature was increased and crystallinity was decreased when nanocapsules were introduced into PA6.The tribological properties of PA6 self-lubricating composites under different friction conditions（sliding speed,load and temperature）were investigated.At room temperature,friction coefficient and wear rate of the PA6 composites with 3 wt.%nanocapsules were reduced by38.9%and 60.5%,respectively,compared with pure PA6.SiO₂ and ionic liquid synergistically contributed to the improvement of tribological properties of PA6 composites.The sliding speed（200,300 and 400 rpm）had little effect on the frication coefficient and wear rate of PA6composited.As the friction load increase（from 30 to 70 N）,the friction coefficient decreased and the wear rate increased.When the friction temperature was 20-100℃,the friction coefficient and wear rate of composites had little change.When the friction temperature increased to 140℃,mechanical relaxation and plastic deformation increased the friction coefficient and wear rate of the PA6 composites.（3）Porous hollow glass was prepared by subcritical water treatment method.The effect of temperature and time of subcritical water treatment on pore morphology and structure of hollow glass were discussed,and the formation mechanism of pore structure was studied.High-temperature resistance IL@hollow glass microcapsules with core content of 63.0 wt.%and average particles size of 20μm were prepared by using porous hollow glass as microcontainers to load IL.Microcapsules had high thermal stability,and the initial thermal decomposition temperature could reach 340℃.PA6 self-lubricating composites containing IL@hollow glass microcapsules showed excellent friction and wear properties.At room temperature,when the microcapsules content was 15 wt.%,compared with pure PA6,the friction coefficient and wear rate of the PA6 composites were reduced by 73.3%and 92.8%,respectively.At high temperature,the friction coefficient and wear rate increased slightly with the increase of friction temperature.The microstructure analysis of friction surface revealed that the formation of uniform self-lubricating transfer film and the effect capture of debris by the cavity left by ruptured microcapsules during friction process synergistically contributed to the effective improvement of tribological properties of PA6 composites.（4）Linseed oil@glass/wax double-wall microcapsules with 50 wt.%core content and 20μm average diameter were prepared by using porous hollow glass to load linseed oil self-healing agent,and solid wax as the encapsulation materials.A self-healing and self-lubricating dual-functional epoxy coatings containing Linseed oil@glass/wax microcapsules were prepared on Q235 steel plate.The results of saltwater immersion and EIS tests showed that the epoxy coating containing 10 wt.%microcapsules had excellent corrosion resistant.Compared with pure epoxy,the impedance modulus increased by 4-5 orders of magnitude during the experimental period.The friction experiments showed that the epoxy coating containing 10 wt.%microcapsules had the best tribological properties.The friction coefficient and wear rate were reduced by 87.8%and 96.3%,respectively,compared with the pure epoxy coating.The microstructure analysis showed that the linseed oil released from ruptured microcapsules could form cross-linked polymer film on the damaged area of the coating,which made the coating have self-healing function and anti-corrosion properties.The synergistic action of linseed oil in the core material and wax in the wall material of microcapsules formed a self-lubricating transfer film on the friction surface,giving the functional coating excellent self-lubrication and friction and wear properties.