Study On Synthesis Technology And Properties Of High Molecular Weight Poly(Tetramethylene Adipamide)

Poly(tetramethylene adipamide)(PA46), one of the most modern advancedmacromolecular materials, is a kind of high-performance engineering plastics withexcellent mechanical and thermal properties. In order to break the monopolization ofDSM Corporation and make preliminary exploration on the industrialization ofpolyamide46in our country, a detailed study for the synthesis process of polyamide46polyamide was made in this paper, aiming that the one with high molecularweight.In this work, polyamide46is synthesized using1,4-diaminobutane and1,6-adipic acid as raw materials. The product is obtained by the following three steps:(1) polyamide46salt is prepared by diamine and adipic acid as two ingredients inthe solvent;(2) prepolymerization is conducted using the prepared polyamide46saltas raw material;(3) the prepolymer are broken into particles for solid statepolycondensation. The synthesis process of PA46was studied systematically in bothglass tube reactors and stainless steel autoclave reactors. And the influence ofreaction conditions included ratio of raw material, reaction temperature, reactionpressure and reaction time on reaction process and products were also studiedsystematically so as to explore the optimum synthesis technology of polyamide46.The structure and thermal properties of the products were characterized by means ofFourier transform infrared spectrometer(FT-IR), Nuclear magnetic resonancespectroscopy (1H-NMR), Differential scanning calorimetry (DSC), Thermalgravimetric analysis (TG) and X ray diffraction (XRD) method.The optimum synthetic technology are as follows:(1) nylon46salt wasprepared in ethanol and the pH of a1%solution in water is7.3when the excess ofdiamine present in the salt is4mol.%.（2）the prepolymerization was firstly carriedout at190℃for5.5h under the pressure of1MPa by stepwise heating. In the processof the reaction, the excess3mol.%of diamine is used to supply the loss one.（3）themaximum viscosity average molecular weight of3.8×104is obtained for polyamide 46under the condition that the solid state polycondensation is performed at270℃for8h.The chemical structure of the products was characterized by Fouriertransform infrared spectroscopy (FT-IR) and Nuclear magnetic resonancespectroscopy (1H-NMR), the result of which reveals that the polyamide46wassuccessfully synthesized. XRD results show that polyamide46is the typical nylonstructure of triclinic system. The thermal properties of product was characterizedby Differential scanning calorimetry (DSC) and Thermogravimetry (TG). It wasfound that the melting point of polyamide46was290-295℃, the highest relativecrystallinity of the product reached48.3%. And the initial decomposition ofpolyamide46is390℃, the maximum rate of decomposition temperature is450℃.Thus polyamide46prove to be a kind of elevated temperature material withexcellent properties.