Preparation Of Porous Polyurea Materials Through Interfacial Polymerization

Interface polymerization in water phase was used to synthesize polyurea(PU)microspheres of large size with porous structure.The polymerization is based on the reaction between isocyanate group and active hydrogen compounds such as water and polyamine.The monomers in this work are toluene diisocyanate(TDI)and ethylene diamine(EDA).TDI was added through a syringe equipped with a pump.Effects of the inner diameter(ID)of the syringe needle and the monomer addition rate on the final size of microspheres were studied.Factors affecting the morphology and structure of the microspheres,including polymerization time,temperature and EDA-TDI molar ratio,etc.,were also studied.The amount of the amino group on the PU microsphere was measured.Both inner and outside morphology of the microsphere were characterized by optical and scanning electron microscope(SEM);the porous properties were determined by Hg intrusion;the thermal property of the microspheres was characterized by thermo-gravimetric analysis and differential scanning calorimetry;the crystallization of the microspheres was tested by X-ray diffraction.The results demonstrate that uniform and porous PU microspheres,with the diameter varieds from 400 ?m to 750 ?m can be synthesized.With EDA/TDI molar ratio at 1/7,highly uniform porous microspheres with smooth surface can be achieved when polymerization is carried out at 65 °C for 5 h after the completion of TDI addition.The amino group on the microspheres surfaces is determined to be 1.179×10-8 mmol/cm2(0.071/nm2).SEM observation shows that the microsphere is coarse on the surface while porous inside.The specific area of the microsphere is 8.2 m2/g,with the pore volume of 0.4 cm3/g,and the porosity of 31%.From different tests,it is show that the PU microspheres have good heat resistance;and 41% of crystallinity.PU polymer structure is also characterized through 1H and 13 C NMR,and based on the results obtained from PU microspheres at different polymerization time,it is concluded that the TDI on the droplet surface reacts firstly with EDA to form a hard shell,the result of the TDI is polymerized with H2 O.When EDA is charged to the reaction system,the outcome PU of different morphology can be achieved depending on the EDA amount.A bead chain-like polymer is observed when the molar ratio of EDA/TDI is 1.43.The size of the bead chain-like polymer can be changed by changing either the ID of the syring neddle or the TDI addition,or both together.Uniform bead chain-like polymer is obtained when the polymerization is run at 68 °C for 5 h.SEM test shows that the beads are smooth outside and porous inside.The pore volume of this PU materal is 0.3 cm3/g,and the porosity is 26%.With the ID of the syringe needle at 300 ?m,and the TDI addition rate at 140 mL/h,uniform stick-like PU is achieved.The diameter of the stick-like PU can be adjusted by changing the ID of the syringe needle.The stick-like PU with uniform size is obtained with the polymerization at 75 °C for 5 h while the moral ratio of EDA/TDI is kept at 1.59.SEM test shows the polymer stick is of smooth surface and porous inside.