Synthesis And Modification Of Nylon 65 Based Itaconic Acid

Nylon is the general name of high molecular polymers with amide bonds repeat structure in the main chain.Because of its good wear resistance,excellent chemical resistance and outstanding impact resistance,it is widely used in various fields of national life,such as automobile parts,oil pipelines,electronic parts,gears,connectors,coating materials and medical applications.With the sustainable development of society,people put forward an urgent demand for high-performance,functional and green polyamide.Therefore,in this paper,a new type of semi biological nylon 65 with pyrrolidone ring on the main chain was synthesized by melt polycondensation from binary acid and binary amine.Around the structural design and molecular chain assembly of polyamide,the synthesis and modification of solubility,water uptake and flame retardant polyamide were studied.Itaconic acid based nylon 65 was synthesized by melt polycondensation from itaconic acid,glutaric acid and hexanediamine.A series of itaconic acid based polyamides with various properties were obtained by adjusting the molar ratio of the two dicarboxylic acids.In other words,a new polyamide containing pyrrolidone ring in the main chain was obtained by the introduction of unsaturated dicarboxylic acid,which gave nylon 65 some characteristics diverse from traditional polyamides.It was found that with the increasing content of itaconic acid,due to the rigid pyrrolidone ring structure destroying the regularity of flexible molecular segments,the transparency of nylon 65 was higher and higher,and gently changed from crystalline state to amorphous state;The results showed that the amount of carbon residue in nylon 65increased gradually,and the heat resistance was fine.When the content of itaconic acid was more than 75%,the solubility of itaconic acid based nylon 65 was enhanced generally,and even could be dissolved in alcohol solvents.Based on the solubility of polyitaconate hexamethylene diamine in solvent N,N-dimethylformamide,the crosslinking agent glycerol was introduced into the molecular structure of polyitaconate hexamethylene diamine,and the migration of hydrophilic groups of polyamide to the surface was inhibited through the crosslinking network formed in the polymer,so as to reduce its water uptake.The effects of the molar ratio of soft chain segment and crosslinking agent on the water uptake,hydrophilicity and mechanical properties of the synthesized polyamide elastomer were investigated.The static contact angle test demonstrated that the synthesized polyamide elastomers were hydrophilic elastomers,but the hydrophilic degree decreased with the increase of glycerol content by inches,and the water uptake of polyamide decreased from 3.21 wt%to 1.21 wt%;Moreover,the synthesized polyamide elastomer had widely adjustable mechanical properties.With the change of crosslinking degree,its elongation at break and tensile strength could vary between 568-5264%and 3.21-46.17MPa separately,the Young's modulus and toughness could reach 74.9 MPa and 216.4MJ/m~3.Finally,the conductivity test indicated that polyamide elastomer could be used as a tensile sensor for sensing human micro motion after spraying carbon nanotube aqueous solution.Using isocyanate terminated polyamide prepolymer as hard segment,polypropylene glycol as soft segment and triethanolamine as crosslinking agent,polyamide elastomer was flame retardant modified(IAHDP-x)by adding reactive P flame retardant and P/N synergistic flame retardant mechanism.Its tensile properties,fatigue resistance,self recovery and tear resistance were investigated.The results revealed that the synthesized phosphorus flame retardant(DDP)could not only enhance the flame retardancy,but also strengthen the mechanical properties of polyamide.Among them,the limiting oxygen index and UL-94 of IAHDP-1.2 were27.6%and V-0 respectively,indicating that it could be used as flame retardant material;Cyclic tensile test demonstrated that it had good fatigue resistance and self recovery;Besides,the tear resistance of IAHDP-1.2 could reach 35.24 k J/m~2.Interestingly,IAHDP-1.2 also displayed shape memory characteristics,and the sample could be restored to its original state at 60?.The polyamide spline was placed in the oven under the condition of applying external force(60?,15 min).After removing the external force,the spline could maintain a fixed shape at room temperature,and then put the spline in the oven to restore to its original state.In this paper,a series of itaconic acid based nylon 65 with different properties were synthesized by adjusting the molar ratio of two dicarboxylic acids,and its structure and properties were analyzed.The results showed that polyhexanediamine itaconic acid could be dissolved in weak polar solvent DMF;Then,using this characteristic,the isocyanate terminated polyamide prepolymer was prepared by solution polycondensation.Glycerol was introduced into the above structure as a crosslinking agent to inhibit the migration of polyamide hydrophilic groups to the surface through the crosslinking network formed in the polymer,so as to reduce its water uptake;Finally,the synthetic polyamide elastomer was flame retardant modified with reactive P-flame retardant,and the polyamide elastomer with permanent flame retardant was successfully prepared,which provided a theoretical and experimental basis for its application in the field with high demand for dimensional stability and flame retardancy.