Preparation Of Nylon6with High Viscosity By Different Chain-extension And Characterization

Nylon6（PA6）is an engineering plastic with excellent overall performances.Generally,themolecular weights of nylon6prepared by traditional polymerization is difficult to meet therequirement of engineering plastic.We are currently using the melt and chain extensionreaction method to improve the viscosity and the molecular weight of nylon6.The intrinsicviscosity,melt index,mechanical properties,crystallization properties and other aspects ofnylon6and the chain-extendered products were respectively investigated by ubbelohdeviscometer,melt plastometers,polarized optical microscopy (POM) and differential scanningcalorimeter (DSC),etc.The result of all the performance showed that the bisoxazoline is more effective than theepoxy resin as chain extender.There is an optimal amount of the two kinds of chain extender.0.9wt%of the bisoxazoline enables the intrinsic viscosity of nylon6reach1.80dL/g,themolecular weight from17000up to33500.0.6wt%of the epoxy resin can make the viscosityof nylon6increase to1.56dL/g.The mechanical properties of the chain-extension of PA6haveimproved significantly.The melting behavior and crystallization kinetics of PA6and PA6/Bisoxazoline blendswere studied and analyzed by DSC.The study results on the isothermal crystallization kineticsshowed that Avrami equation could describe isothermal crystallization process of PA6and itsblends very well.The rate of crystallization of PA6was reduced and the growth of crystalnuclei was hindered by the addition of the bisoxazoline.The equilibrium melting point ofPA6/Bisoxazoline blends obtained by Hoffman-Weeks theory was lower than that of purePA6,which indicated that the addition of the bisoxazoline decreased the perfection degree ofcrystallization of PA6.The analysis of non-isothermal crystallization showed that the Avramiequation modified by Jeziomy and Mo methods are all applicable to the non-isothermalcrystallization process of PA6and PA6/Bisoxazoline blends. At the same rate of cooling, thecrystallization rate constant of chain-extended PA6was less than pure PA6, and in order toachieve the same degree of crystallinity, the cooling rate of chain-extended PA6shoud be greater than that of pure PA6, which indicated that the addition of the bisoxazoline reducedthe rate of crystal growth and hindered the growth of crystal nuclei.