氮化硼/超支化聚硅氧烷-聚酰亚胺粘结固体润滑涂层的性能

Properties of Boron Nitride/Hyperbranched Polysiloxane-Polyimide Bonded Solid Lubricant Coating

通过“一步法”设计制备了端氨基超支化聚硅氧烷(HBPSi-NH2)-聚酰胺酸(PAA)粘结剂(HBPSi-PAA),然后利用喷涂法将其与固体润滑剂聚多巴胺包覆的球磨剥离六方氮化硼(PDA@exf-h-BN)纳米片喷涂在马口铁表面,经固化后制备出PDA@exf-h-BN/HBPSi-PI粘结固体润滑涂层.采用MMUD-1B型摩擦磨损试验机和SDTA 85热失重分析仪分别对涂层的摩擦学性能和热性能进行了研究,并对其摩擦机理进行了初步探讨.结果表明:当HBPSiNH2和PDA@exf-h-BN的引入量分别为10.0%(质量分数)和12.0%(质量分数)时,粘结固体润滑涂层的摩擦系数稳定在0.12,相比纯PI涂层降低了约65.7%,耐磨寿命可达60 min,并且初始分解温度从319.8℃提升至545.6℃,残余质量达到74.6%,其优异的摩擦学性能和热稳定性主要归因于HBPSi-NH2和PDA@exf-h-BN的“软-硬”粒子协同减摩抗磨效应以及二者所赋予涂层优异的热稳定性.

Polyimide(PI),as one of most promising high-performance and multi-functional polymeric materials,has been widely applied in the field of aerospace and aviation.However,as the lubricating materials,PI has been greatly limited by high wear and high friction coefficient,especially in some extreme working conditions.In this work,the amino-terminated hyperbranched polysiloxane(HBPSi-NH),which had the characteristics of flexible segment and low surface energy,was incorporated into the main chain of polyamic acid(PAA) molecular through the one-step approach to obtain coating binder material(HBPSi-PAA).Then,hexagonal boron nitride nanosheets coated with polydopamine(PDA@exf-h-BN),of excellent lubricity,wear resistance and heat resistance were used as a solid lubricant.HBPSi-PAA was sprayed on the surface of tinplate by spraying method.After curing,PDA@exf-h-BN/HBPSi-PI bonded solid lubricating coating was obtained.And then,the MMUD-1B friction tester and the SDTA 85 thermal weight loss analyzer were used to study the tribological and thermal properties of the coating,and the friction and wear mechanism was discussed.The results showed that the friction coefficient of the PI coating showed a trend of first decreasing and then increasing with the HBPSi-NHloading,while the wear resistance life showed a trend of first increasing and then decreasing.When 10.0%(mass fraction) HBPSi-NHwas introduced into the PI coating(the coating was noted as10.0% HBPSi-PI),the friction coefficient of 10.0% HBPSi-PI coating was as low as 0.24 and the wear resistance life reached 60 min.When a certain amount of PDA@exf-h-BN was introduced into the 10.0% HBPSi-PI coating,the friction coefficient and wear life of the PDA@exf-h-BN/HBPSi-PI bonded solid lubricating coating were greatly improved compared to the HBPSi-PI coating.As the increase of PDA@exf-h-BN,the friction coefficient of the PDA@exf-h-BN/HBPSi-PI bonded solid lubricating coating gradually decreased,and the wear resistance life also showed a trend of first decreasing and then increasing.Among them,when the addition of PDA@exf-h-BN was 12%(mass fraction),the friction coefficient of 12% PDA@exf-h-BN/10.0% HBPSi-PI bonded solid lubricating coating was stabilized at 0.12,the wear life reached 60 min.Meanwhile,the initial decomposition temperature increased from 319.8 ℃ to 545.6 ℃,the residual mass reached 74.6%.It not only showed excellent tribological properties,but also showed excellent thermal stability.This was mainly attributed to the synergistic friction reduction and wear resistance of the “soft-hard” particles between HBPSi-NHand PDA@exf-h-BN,and the good thermal stability they provide to the coating.This research provided the possibility to develop high-performance,multi-functional bonded solid lubricating coatings in aerospace,chemical industry,microelectronics and other high-tech fields.It also laid a corresponding theoretical foundation for the research of the novel hyperbranched polysiloxane containing Si-O-C structure in the field of friction.