Research On Fused Deposition Modeling Of Polycarbonate Alloy

With the development of material molding technology,additive manufacturing technology?also known as 3D printing?meets the requirements of various industries for personalized customization and complex shape design,which attracts widespread attention.Fused deposition modeling?FDM?is the most widely used 3D printing technology because of its advantages of simple principle,low cost,and convenient operation.At present,the types of commercial materials available for FDM are limited,such as acrylonitrile-butadiene-styrene copolymer?ABS?and polylactic acid?PLA?,etc.Many engineering plastics such as polycarbonate?PC?itself have excellent comprehensive performance,but it cannot be applied to common FDM printers due to the poor processability of PC,which limits the application of PC in FDM.At present,expanding the types of printing materials,improving the performance of printing materials,and realizing the functionalization of printing materials are the main directions of FDM materials research.Based on this,this paper prepared PC/polybutylene-adipate terephthalate?PBAT?and PC/PLA alloy with good printability for FDM by melt blending.The paper systematically studied the property and structure of two PC alloy material and fabricated PC/PLA alloy with high thermal conductivity using hexagonal boron nitride?BN?as thermal conductive filler through FDM.This work was significant to expand the types of FDM materials and achieve the functional application of FDM.PC has high melt viscosity and glass-transition temperature?T_g?,and common FDM printing equipment cannot meet the processing requirements of PC.The PC/PBAT alloy was prepared by melt blending.The processing properties,thermal properties,mechanical properties and micro-morphology of the PC/PBAT alloy were systematically studied.The results showed that the addition of PBAT significantly improved the processing performance of PC and reduced the processing temperature and melt viscosity of PC.PC/PBAT alloy was fully compatible system and PC/PBAT was a single continuous phase with transparency.The T_g of alloy decreased with the increase of PBAT content.The introduction of PBAT had little effect on the strength but reduced the toughness of PC.The toughness of the alloy material was improved by adding the toughening agent methyl methacrylate-butadiene-styrene terpolymer?MBS?.On this basis,the printing performance of PC/PBAT materials was studied using FDM technology,and the results showed that the T_g of alloy was matched to the temperature of printing platform by adjusting the PBAT content,which achieved the printability of PC.The addition of MBS would not affect the printing performance.Compared with injection molding samples,the mechanical properties of FDM products were lower due to the layer-by-layer forming characteristics and corresponding voids generated by layer-by-layer structure.PLA is a common material for FDM and in this paper,the PC/PLA alloy was prepared by melt blending technology and modified by ethylene-butyl acrylate-glyceryl methacrylate ternary polyester?PTW?.The processing properties,mechanical properties,thermal properties and micro-morphology of PC/PLA alloy and PC/PLA/PTW alloy were systematically studied.The results showed that PLA could significantly improve the processability of PC and slightly increased the strength and modulus of the blends at the same time,but the toughness of the alloy material decreased.The introduction of PTW improved the toughness of the system.When the PTW content was up to 10 phr,the impact strength of PC-PLA40/PTW-10 was 61.7 k J/m²which was 9.1 times that of PC-PLA40,making the toughness of the alloy equivalent to pure PC?68.1 k J/m²?.PC/PLA alloy was an typical incompatible system with two independent T_gand the addition of PTW would not change the respective T_g of the PC/PLA alloy but inhibit the crystallization of PLA.PLA changed from spherical dispersed phase to semi-continuous phase as the content of PLA increased,and PTW was dispersed in the PC/PLA alloy in the form of dispersed phase,reducing the interfacial gap between PC and PLA.On this basis,the printing performance of PC/PLA alloy was studied using FDM technology.The results showed that with the increase of PLA content,the adhesion and printing performance of the filament were improved,while the addition of PTW reduced the printing warpage.Therefore,PC/PLA/PTW alloy had good printing performance.The temperature gradient distribution in FDM products and the influence of the printing platform temperature on the crystallinity were studied.It was found that the temperature gradient distribution would cause the crystal gradient distribution in the Z-axis direction.Based on the PC-PLA40/PTW-10,five printing methods were designed to study the effect of printing direction on the mechanical properties of FDM products.The results showed that the reason for the difference in mechanical properties was that different printing directions would result in different force directions and failure methods.Using PC-PLA40/PTW-10 as the polymer matrix?PM?and hexagonal boron nitride?BN?as the thermal conductive filler,PM/BN thermally conductive composites were prepared,and the printing performance of PM/BN composites was studied through FDM technology.The results showed that BN would slightly reduce the strength of the system but not affect the printing performance of the composites,and BN would promote the crystallization of the PLA.Two printing methods of“Flat-Cross”?FC?and“Stand-in-Order”?SO?were designed to study the through plane thermal conductivity?TPTC?of the composites.The research results showed that,compared with the compression molding?CM?,the TPTC of two printing methods showed the rule of TPTC_SO>TPTC_CM>TPTC_FC.The fiber shaped carbon fiber?CF?and spherical aluminum powder?s-Al?affected the TPTC of the composites as the same as BN.The influence of filler shape on the degree of anisotropy of thermal conductivity enhancement was studied,and it was found that two-dimensional filler was easier to form thermal conduction path than one-dimensional filler.The anisotropic filler would be oriented along the nozzle scanning direction during the FDM printing process,and the samples had the largest TPTC when the filler orientation direction was consistent with the through plane direction.