Preparation And FDM Molding Process Of Sepiolite Mineral Fiber Modified Nylon 12 Composite

In 3D printing technology,fused deposition modeling(FDM)is the most popular rapid prototyping method because of its advantages of simple equipment,clean process and low operating cost.Nylon 12 is one of the most widely used FDM materials because of its good thermodynamic properties and suitable melt viscosity.Due to the limitation of molding process,there will be some holes in the inner part of nylon 12 FDM,especially in the interlayer,which results in its mechanical properties generally lower than that of injection molded parts.At the same time,due to the high coefficient of thermal expansion,warpage is easy to occur in the FDM process of nylon 12,and the dimensional accuracy of the molded parts needs to be improved.In this paper,sepiolite mineral fiber(sepiolite or attapulgite)was selected as modifier to improve the interface adhesion between the filler and the matrix,realize the uniform dispersion of the mineral fiber in the matrix,optimize the mechanical properties,temperature resistance and mechanical properties of the composite The orientation of mineral fiber in the matrix is guided by the adjustment of key process parameters such as printing direction,speed and temperature,so as to further optimize the comprehensive properties of nylon 12 composite printings.The research results of this paper mainly cover the following three aspects:(1)By using twin-screw mixing process and optimizing extrusion temperature and speed,the homogeneous dispersion of micro sepiolite fiber(SEP)and nano attapulgite fiber(ATP)in nylon 12 matrix was realized.By adjusting the process parameters of the extrusion system,PA12 / SEP and PA12 / ATP composite FDM wires with different doping ratio were successfully prepared,which could be printed by FDM printer.(2)The results of tensile,bending,DMA and dimensional accuracy tests show that the addition of proper SEP can significantly improve the comprehensive mechanical properties and forming accuracy of PA12 FDM printings,and optimize the temperature resistance.The morphology of PA12 / SEP FDM was observed,and it was found that SEP had obvious orientation behavior.When the content of SEP is 10 wt%,the comprehensive properties of PA12/SEP FDM printing samples are the best.The tensile strength and tensile modulus are 132% and 175% of PA12 respectively,and the bending modulus and bending strength are 186% and 160% of PA12 respectively.At the same time,the thermal expansion coefficient of the composite material is obviously reduced,and the dimensional accuracy of the molded parts is obviously improved.(3)The addition of ATP can significantly improve the comprehensive mechanical properties and forming accuracy of PA12 FDM.At the same time,PA12/ATP FDM has obvious printing orientation behavior.When the content of ATP is 15 wt%,the comprehensive performance of PA12/ATP FDM printing sample is the best.Compared with SEP,ATP can improve the tensile and bending properties of PA12 composite FDM printings more obviously because of its nano scale fiber properties,and change the glass transition temperature less,and reduce the thermal expansion coefficient more significantly.