Study On The Reaction Characteristics Of Room Temperature Casting Polyurethane Curing System By The Optical Microrheological

Room temperature curing cast polyurethane has attracted more and more attention due to its energy saving,convenient operation,adaptability to environmental protection requirements,and better cost performance for end products,which has greatly expanded the diversified development of polyurethane materials.Since microfluidics is closely related to the microstructure of the system,this is an important part of studying the curing reaction of room-temperature cast polyurethane.The main research works were as follows:(1)Synthesis of low viscosity liquefied modified MDI with 4,4'-diphenylmethane diisocyanate(MDI),monohydric small molecule alcohols and macropolyols.To study the effect of different reaction conditions on the viscosity of liquefied modified MDI.Structural characterization using infrared spectroscopy,rotary viscometer,automatic potentiometric titrator and optical micro-rheometer.The results showed that the liquefied modified MDI synthesized by adjusting the optimal reaction conditions had an NCO content of 18%?21%,a viscosity of 310?360 mPa·s,and stability.(2)Optical microfluidic method was used to study the kinetics of polyether-polyurethanes at room temperature and compared with infrared spectroscopy.The results show that the optical microrheological method can be used to study the kinetic reaction of the polyether polyurethane curing process.This was consistent with the infrared spectroscopy research results.The curing reaction satisfies the secondary reaction,and gradually deviates from the secondary reaction at the later stage,and the optical microrheological method can given the gelation time of the catalytic reaction of different systems and the reactivity after gelation.(3)Study on the reactivity of different catalysts with liquid MDI prepared polyurethanes by optical microrheology.Characterization of products using universal electronic testers,dynamic thermomechanical instruments and infrared spectroscopy.The results showed that the catalytic properties of different catalysts were different.By adjusting the type of catalyst and the amount of catalyst,an elastomer with a tensile strength of 25 MPa and an elongation at break of 300%were prepared.(4)Study on the reactivity of different polyols compounds with liquid MDI prepared polyurethanes by optical microrheology.Structural characterization using infrared spectroscopy,scanning electron microscopy,and polarized light microscopy.The results show that the molecular crystallization of the molecular chain easily leads to phase separation of the system and it was difficult to form a cross-linked network structure.The presence of side groups and double bonds facilitates the preparation of the elastomer.