The Research On Modified PBT For Fused Deposition Modeling

Poly(butylene terephthalate)(PBT) is one of the most frequently used engineering thermoplastic materials with a wide range of applications,it has high heat resistance, good mechanical strength and rigidity, good chemical resistance, good electrical insulation properties and lubricity. Though it shows excellent processability but the solidification time of pure PBT is too short to be used as a 3D printing candidate materials, and neat PBT materials fail in a brittle manner under certain loading conditions such as in notched impact testing. A modified poly(butylene terephalate)(MPBT) containing poly(butylene terephalate-co-isophthalate)(PBTI) and poly(butylene terephalate-co-isophthalate-co-sebacate)(PBTIS) were prepared for fused deposition modeling by direct esterification and subsequent polycondensation using PIA and SA to replace part PTA.The molecular weight and distribution, melting point(Tm) and the glass transition temperature(Tg) of PBTI were characterized by Gel Permeation Chromatography(GPC), 1H-NMR spectrometer and differential scanning calorimetry(DSC). An Universal testing machine and impact tester were used to measure the tensile strength, flexural strength, notch impact strength and elongation at break, and the candidate mole ratio was n(PTA):n(PIA)-7:3.When n(PTA):n(PIA) was held constant at 7:3, the effects of the mole content of SA (3-7%) on the thermal, rheological and mechanical properties of PBTIS were investigated, too. The molecular weight and distribution of PBTIS were characterized by GPC and’H-NMR spectrometer. The melting behaviors and isothermal crystallization kinetics of PBTIS were characterized by DSC. The viscosity and melt flow rate of PBTIS were measured by brookfield viscometer and melt indexer. An Universal testing machine and impact tester were used to measure the mechanical properties of PBTIS. The results show that when the mole content of SA is 5%, the samples show good melting point(Tm=174℃)and excellent mechanical properties(Tensile Strength=55.4MPa;Flexural strength=83.7MPa;Notched impact strength=5.7kJ/m2). Then the samples of PBTIS were changed to filaments by a desktop drawing machine and printed using a 3D printer, which could be printed fluently.