Synthesis Of Novel Hyperbranched Polymer And Its Application In 3D Printing

3D printing has been developing rapidly in recent years and has been applied in academic and industry areas because of the advantages in complicated model manufacture and personal design.Photopolymerization-based 3D printing is the earliest and most mature technique among lots of technologies.But there are some disadvantages about photopolymerization-based 3D printing,such as long manufacturing time and poor mechanical properties,which limit its development.Therefore,it is important to develop photosensitive resin with high precision,fast speed of curing and good mechanical property.Hyperbranched polymer is highly branched macromolecule with a great number of functional groups,high solubility and low melting viscosity and its structure is irregular.Hyperbranched polymer is simple to synthesize and there is no need to highly purify them.These characters of hyperbranched polymers are suitable for industrial applications,especially for photosensitive resin.The synthesis of hyperbranched polymer and its application in 3D printing in this paper are shown below:1.AB₂ monomers were obtained through the reaction of isophorone diisocyanate（IPDI）with hydroxy of dimethylolbutyric acid（DMBA）.Hyperbranched polymer was synthesized through the reaction of carboxyl with isocyanate in AB₂ monomers catalyzed by magnesium stearate.Hydroxyethyl acrylate（HEA）was used to terminate the reaction to obtain polymer with crystallization which could be polymerized.The structure of hyperbranched polymer and reaction process were studied by ¹H NMR and FT-IR and the test showed the successful synthesis of expected structure.Three generations of hyperbranched polymer were obtained by controlling the NCO content in the condensation of AB₂ monomers and they were characterized in various ways.The tests showed that the molecular weight distribution was broad.The polymerization temperature of hyperbranched polymer increased as the increase of generation and there was crystal structure in all polymer whose melting point was about 288℃.2.To further lower the cost and reaction time,more active and cheaper reactant toluene diisocyanate（TDI）was used to react with DMBA to synthesize hyperbranched polymer just like IPDI.Three generations of hyperbranched polymer were obtained by controlling the NCO content in the condensation of AB₂ monomers and they were characterized.The tests showed that the molecular weight was broad.The polymerization temperature of hyperbranched polymer increased as the increase of generation and there was crystal structure in all polymer whose melting point was about288℃.The results showed that hyperbranched polymer produced by TDI needed lower temperature and short reaction time comparing with that produced by IPDI and the molecular weight distribution of former was narrower than the latter.3.The influence of oligomer content on property of photosensitive resin was studied by adjusting the ratio of hyperbranched polymer and reactive monomers.The viscosity and rheological property of photosensitive resin produced by different hyperbranched polymer was studied.The mechanical properties of the samples printed by LCD 3D printer were tested and influence of exposure time was studied.The results showed mechanical properties of every resin were excellent.The best combination properties in IPDI system,was 25%of IPDI-3 resin which printed at 6 s exposure time.Tensile,flexural and impact strength were 42.98 MPa,116.06 MPa and 34.59 KJ/m²respectively.The good combination properties in TDI system,was 25%content of TDI-3 resin which printed at 6 s exposure time,whose tensile,flexural and impact strength were 46.61 MPa,145.88 MPa and 29.23 KJ/m².The 27.5%content of TDI-3 resin also had good property but its viscosity was higher than 25%content of TDI-3 resin.Tensile strength,flexural strength and impact strength were 66.24 MPa,136.08 MPa and 26.40KJ/m².Flexural and impact strength of all samples were improved obviously comparing with commercial resin.