| In recent years,3D printing technology especially selective laser sintering technology(SLS)has developed rapidly.Because of its regular molecular chain,nylon(PA)materials have a high sintering rate and a high sintering rate when laser sintering,and the mechanical properties of the formed parts are good.At present,nylon 3D printing materials are mostly imported nylon 12 and nylon 11,and domestic research on long carbon chain nylon for 3D printing is few.In this paper,from the perspective of developing long-chain nylon 1212 with domestic proprietary property for 3D printing,firstly,an effective way to widen the sintering window temperature of nylon 1212 material was studied from the preparation process.Next,the sintering properties of nylon 1212/glass microbeads(PA1212/GB)and nylon 1212/carbon fiber(PA1212/CF)composites with glass beads and carbon fibers as fillers were studied.Finally,in order to reduce the performance of nylon 1212 after sintering 2～3 times,the bonding performance between nylon 1212 and steel was studied by using nylon 1212 powder.The main contents of this paper are as follows:(1)In order to investigate the effect of the amount of nylon 1010 salt on the melting temperature and crystallization temperature of nylon 1212/nylon 1010 composite,nylon 1010 salt was copolymerized with nylon 1212 salt in an amount of 2wt.%,4 wt.%,6 wt.%.,8 wt%,10 wt.%,12 wt.%.The results show that the addition of nylon 1010 copolymerization component can broaden the temperature window of nylon 1212 selective laser sintering and improve the processability of nylon 1212 powder.When nylon 1010 is added at 4wt.%,its melting point is 181.6℃,the crystallization temperature was 148.0℃,the sintering processing window temperature was 21.2℃,and the sintering window was widened by 5.4℃.Adding 4wt.%of nylon 1010 salt during polymerization can maintain the excellent performance of nylon 1212 while maintaining the high SLS processing performance.(2)Nylon 1212/glass microbeads and nylon 1212 carbon fiber composites were prepared by mechanical mixing method,and then sintered samples were prepared by SLS molding.To investigate the effects of the addition amount of glass microbeads and carbon fibers on the properties of sintered nylon composites,The composite materials were characterized by universal testing machine,differential scanning calorimetry(DSC),X-ray diffraction(XRD),thermogravimetric analysis(TG),dynamic mechanical analysis(DMA),scanning electron microscopy(SEM).The results show that when the addition amount of glass beads is 30wt%,the tensile strength,flexural strength,elongation at break,notched impact strength and water absorption of PA1212/GB are 49MPa,49 MPa,12%,3.1kJ/m2,0.6%,respectively;when the carbon fiber is added at 20wt.%,the tensile strength,flexural strength,elongation at break,notched impact strength and water absorption of PA1212/CF are 39 MPa,46 MPa,7%,2.5 kJ/m2 1.3%,respectively.When the addition amount of GB is less than 30wt%,and the addition amount of CF is less than 20wt.%,the composite material shows better comprehensive performance.The results of SEM observation show that the increase of mechanical strength is due to the fact that less filler can be well dispersed in the molten nylon 1212 matrix to form a dense structure with good compatibility,when the amount is too much,More mechanical defects appear inside the composite,resulting in a significant decrease in the mechanical properties of the material.(3)The bonding performance between nylon 1212 and steel was studied by using nylon 1212 powder.The nylon 1212 powder was bonded to ASTM 316 steel sheet by hot press,to investigate the effect of the experimental temperature,experimental pressure,the amount added related additives on the bonding properties and wear resistance of nylon 1212,and the test was carried out by universal testing machine,friction and wear tester and polarized light microscope.The results show that when the experimental method of setting the experimental temperature is 205℃ and the experimental pressure is 0.3 MPa,sanding pretreatment by hot press equipment can obtain the bonding strength between nylon 1212 powder material and metal.When the formula of nylon 1212 powder is:when the component one is added in an amount of 10wt.%,the bonding strength of nylon 1212 is 30MPa,the friction coefficient is 0.17,the wear amount is 0.11 g,which shows better bonding and wear resistance performance.In this paper,nylon 1212 was selected as a substitute for nylon 11 and nylon 12 to develop selective laser sintering powder,which provides material guarantee for domestic SLS molding technology and contributes to the development of high-end manufacturing technology and high-performance nylon materials.The application of nylon 1212 in the wear-resistant impact coating of SLS nylon 1212 powder has great significance in solving the problem of recycling of nylon 1212 powder and turbine abrasion protection. |
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