| Polyimide(PI),which is known as "the gold of plastics" in the field of special engineering plastics,owing to its excellent heat resistance,mechanical properties,chemical stability and wear resistance.Therefore,PI plays an important role in the field of microelectronics,semiconductor assembly,aerospace,weapons,equipment and satellite manufacturing.However,most of the PI materials used in the engineering was processed to films,blocks or bars by casting or hot pressing.However,complex structure manufacturing,which has become a bottleneck problem restricting the application and development of PI.In recent years,scientists have developed photosensitive polyimide(PSPI),the combination of 3D printing and PSPI resin system can effectively solve this problem.In this paper,PSPI oligomers grafted with photosensitive groups were synthesized using commercially available diamine and dianhydride monomers.And PSPI resin was prepared by mixing the PSPI oligomers with active diluent,crosslinking agent and photoinitiator.Firstly,the difference of DLP3 D printing and traditional thermosetting manufacturing methods on the properties of polyimide were investigated.Then,the PTFE micro powders were introduced into the PSPI resin to improve the tribological properties.Finally,based on the advantages of“layer by layer”manufacturing of 3D printing technology,the lubrication of devices where it is needed were manufactured by using alternate lubricating 3D printing method.The main conclusions are as follows:(1)Compared with the traditional manufacturing method: casting and thermal treatment,DLP 3D printing has a negative effect on the properties of polyimide,but the effect is not significant.In this paper,DLP 3D printing and casting method are used to manufacture polyimide samples,and its heat resistance,mechanical properties and tribological performance comparison has been studied.The results show that to meet the requirements of photocuring,the incorporation of the active diluent and crosslinking agent have reduced the heat resistance of PSPI materials and tribological properties,but has little effect on mechanical properties.However,DLP 3D printing PSPI has obvious advantages in manufacturing precision or complex structures.(2)To improve the tribological properties of 3D printed PSPI,the PTFE micro powders was introduced to PSPI resin to improve the friction-reduction and anti-wear properties.The result show that the incorporation of PTFE micro powders improves the heat resistance and tribological properties of the composites.Compared with PSPI material,the friction coefficient of the composites is decreased by 88% and the wear rate is decreased by 98%.(3)The 3D printed structure proved that PSPI-PTFE resin has good forming precision.In this paper,to meet the working conditions of special parts that only need to slide on a certain plane or need to slide parallel between a certain layer,two kinds of intelligent lubrication devices are manufactured by surface lubricating and alternate lubricating 3D printing methods.Tribological tests also confirmed that the PSPI-PTFE structure has a significant improvement on friction-reduction and anti-wear properties.With the advantage of 3D printing layer by layer manufacturing,alternate lubricating devices with patterned surface were designed and manufactured by changing PSPI and PSPI-PTFE resin in the 3D printing process.Tribological tests were carried out by frequency conversion and variable load,respectively.The results show that the tribological properties of the devices are not affected by frequency conversion at low frequency.However,in the variable load test,the friction coefficient decreases with the increase of load.Finally,a bearing with characteristics of target-region-lubrication is successfully fabricated.The intelligent manufacturing of PSPI-PTFE composites has great potential in aerospace,weapons and equipment or precise components to meet development manufacturing of lightweight,high performance requirements. |
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