The Molecular Structure Of Synthetic Rubber And Its Relationship With Mooney Viscosity

Mooney viscosity(ML),as an important index to control the quality of rubber for the synthetic rubber production enterprises,is of great significance for the industrial production of rubber.Mooney viscosity changes with molecular structure,but so far the relationship between them is not very clear.Firstly,the molecular structure of butadiene rubber(BR),emulsion polymerized styrene butadiene rubber(SBR)and hydrogenated nitrile rubber(HNBR)were characterized,including molecular mass,molecular mass distribution,gel content and long chain branching density(LCBD).And then,the Mooney viscosity of rubber samples was characterized to discuss the relationship between Mooney viscosity and molecular structure,so that good correlations were obtained between them.The major content and achievements of this dissertion as follows:Based on literature,the processing parameters of synthetic rubber were expounded,and the present research of the relationship between Mooney viscosity and molecular structure of synthetic rubber was summarized.The existing characterization methods and their advantages and disadvantages of the long chain branching degree of polymers were analyzed.And it was found that for the polymer of more complex composition and structure,such as SBR and HNBR,there was little research on the characterization of long chain branching.The molecular mass,molecular mass distribution,gel content and LCBD of BR,SBR and HNBR and their precipitated graded samples were determined respectively.The LCBD were determined by the gel permeation chromatography(GPC)coupled with online eighteen-angle laser light scattering(LS),differential refractive index(DRI)and viscosity(CV)detectors,and the carbon-13 nuclear magnetic resonance spectroscopy(13C-NMR).The results showed that both the two methods are available to measure LCBD.However,for the rubbers with complicated molecular structure,such as HNBR and SBR,the triple-detector GPC is more accurate and convenient,while 13C-NMR was more favorable for the analysis of long chain branched sites.The Mooney viscosity of three kinds of synthetic rubber and its precipitated graded samples was determined.The relationship between Mooney viscosity and the gel content,LCBD,molecular mass and molecular mass distribution were analyzed and discussed.It was found the Mooney viscosity is positively correlated with the gel content,LCBD and molecular mass;the presence of benzene in the polystyrene structure of SBR could inhibit the chain entanglement and reduce the Mooney viscosity;and the increase of 1,2-structure in the HNBR could lead to the increase of the Mooney viscosity.Finally,the correlations between Mooney viscosity and gel content,Mooney viscosity and LCBD,Mooney viscosity and molecular mass correlation were established,which indicated that the obtained correlation is the best between Mooney viscosity and number-average molecular mass for BR and SBR...