Study Of The Molecular Structure And Rheological Properties For Cis-1, 4-Polybutadiene Rubber With Neodymium-based Catalyst

The aim of this work was to study the molecular structure and rheological property of NdBR raw rubber samples which were synthesized by pilot plant in Dushanzi Institute of Petrochemical Industry Company.(1) The microstructure of NdBR samples were charcterized by IR and 1H-NMR. Results showed that NdBR possesses high cis-1,4-unit content in molecule (more than 98%) and good stereospecificity of molecular chain. So it belongs to high cis-1,4-polybutadiene rubber. Besides, there are no any difference nearly among NdBR samples.Because each structure unit has its own clear characteristic peak, IR is better used to quantitative analysis of NdBR.(2) The molecular weight and its distribution were measured by means of viscometry and gel permeation chromatography (GPC). It is found that intrinsic viscosity of NdBR samples varies from 270 to 330 mL/g and the viscosity-average molecular weight varies from 27.7×104 to 36.7×104. Results of GPC show that the number-average molecular weight varies from 15×104 to 17×104, and the weight-average molecular weight varies from 50×104 to 58×104,which is larger than that of NiBR. Polydispersity index ranges from 3.1 to 4.5.(3) The rheological properties of NdBR toluene solution system were performed by using Brookfield DV-Ⅱ+Pro rotational viscometer. To fit the experimental data of shear stress and shear rate, the power law was used. The curve of shear stress with shear rate is coincided with power-law equation, R2 > 0.99. When solution concentration is less than 5.11%, the non-Newtonian index is about 0.94.When solution concentration were between 8% and 12%, the non-Newtonian index is about 0.78.Results indicate that the system exhibit the character of pseudoplastic fluid.(4) The influence of concentration, temperature, shear rate and molecular weight on the viscosity of NdBR solution in toluene were investigated by using the orthogonal experiment analysis method.The order is that concentration>>molecular weight≈shear rate> temperature.The correlative equation between viscosity and concentration,temperature were established based on binary nonlinear regression.