Study On Solid Phase Polycondensation Of Nylon 6 And Its Structural Properties

As one of the five general engineering plastic,nylon 6 is widely used in many industries for its excellent performances.The relative viscosity of nylon 6 used in engineering plastic is required to be above 3.But nylon 6 synthesized by hydrolytic ring-open polymerization can't meet the production requirements for the low relative viscosity.So it is necessary to increase the relative viscosity of nylon 6.In this paper,the solid state polymerization(SSP)was used to increase the relative viscosity and the rheological property of nylon 6 was tested.Finally the kind and dosage of catalysts were studied.In the first part,the production equipment was simulated by continuously passing N2.Different reaction time and temperature were set,and their influences on the results were discussed.The results showed that,at the same temperature,the relative viscosity increased and the growth rate became slow with the increasing time.Finally,they changed little.The higher the temperature was,the more obvious the effect was.The concentrations of-NHZ and-COOH decreased fast,especially during the first 6 hours.The samples maintained the original heat stability,but the lattice parameter changed and there appeared the phenomena called preferred orientation growth.In the second part,different time and temperature were set and the rheological property was studied,especially the relationship between apparent viscosity and shear parameters(stress and rate).The non-Newtonian index n,consistency index K and activation energy for viscous flow ?E were also calculated.The results showed that,the melt of samples were typically non-Newtonian fluid and showed shear-thinning behavior.The melt of samples were pseudoplastic fluid.At the same temperature,the higher the relative viscosity was,the higher the value of K was and the smaller the value of n was.For the same sample,the higher the shear rate was,the lower the value of AE was.At the same shear rate,the higher the shear rate was,the lower the value of?E was.In the last part,the kinds and dosage of catalysts were researched.The catalysts were added to the nylon 6 melt by the twin-screw extruder.Then the relative viscosity was enhanced by the equipment in the first part.The results showed that,different kinds and dosage of catalysts could make different effects and there was a optimal dosage.The relative viscosity of samples was enhanced before melt-extrusion.The catalysts played the role of heterogeneous nucleation.And the crystallization behavior was also studied.