Study On The Synthesis And Properties Of Bio-based Long Carbon Chain Nylon With Cadaverine

With the tension of oil resources and the aggravation of environmental problems,bio-based materials have attracted countries all over the world to invest more in R&D because of their environmental-friendly monomer sources with low carbon emission and high carbon recycling rate.China began late in this field,and all related products have low productivity and single sample type.Most of the premium products are monopolized by foreign companies,such as nylon 11,etc.And overseas have already produced a variety of modified products adapted to different situations.Therefore,the development of novel bio-based nylon materials is of great significance to the industrial development and the expansion of product range in related fields in China.In this study,a series of bio-based nylon 5X（PA5X）products have been synthesized by using cadaverine,a recently developed bio-based monomer,and three different long carbon chain dicarboxylic acids as the primary materials.The salt formation reaction,polymerization process,mechanical properties and polymerization mechanism were also investigated to provide a basis for the development of this PA5X series of bio-based long carbon chain nylon products.In this study,the salts of PA510,PA512 and PA513 were firstly prepared using the reaction of cadaverine with sebacic acid,dodecanedioic acid and tridecanedioic acid,respectively.PA5X was characterized and analyzed by FT-IR,¹H NMR,DSC,TG,and in situ IR technique.The results demonstrated that the structure and composition of PA5X were in line with the anticipated concept and the thermal properties were stable.The pre-polymerization temperature was confirmed to be 170-180°C and the polycondensation reaction was set at 200-220°C as more appropriate.The three PA5X polymers were prepared from PA5X salts by melt polycondensation method,FT-IR,¹H NMR and ¹³C NMR showed the disappearance of PA5X salt structure and the formation of new amide groups.DSC and TG showed the T_m of PA510,PA512,and PA513 were 214℃,209℃,and 204℃,respectively,which decreased with the increase of methylene.The T_c of PA510,PA512,and PA513 were 169°C,168°C and169°C,respectively.The crystalline structures of all three PA5X wereγ-form,with crystallinity of 24.95%,25.95%and 26.72%,respectively.All PA5X have good mechanical properties with yield strength between 54～60 MPa and elongation at break of 219-255%,the flexural strength and impact properties decrease with the increase of methylene.The molecular weight of the polymer increases with the growth of reaction time,up to 40000-50000 in 3h,and the molecular weight distribution index（PDI）is 2.0～2.7,which can meet the actual application requirements.After converting the molecular weight to the polymerization degree and fitting the reaction kinetics to time,the polymerization reactions of PA510,PA512,and PA513 were obtained to be consistent with the third-order reaction,and the kinetic reaction rate constants were 19.79,25.80,and 23.19,respectively.Finally,the non-isothermal crystallization behaviors of PA510,PA512,and PA513 were explored,and the crystallization range and crystallization peak temperatures of all three PA5X moved toward the low temperature region as the cooling rate increased,with PA513 being relatively more susceptible.Jeziorny method analysis shows that the crystallization rate decreases with the increase of cooling rate,the main crystallization stage is heterogeneous nucleation and one-dimensional growth pattern,and the secondary crystallization stage may be heterogeneous nucleation and two-dimensional growth pattern or homogeneous nucleation and one-dimensional growth pattern.The actual crystallization mechanism is more complex and may coexist in many ways.Ozawa’s description of PA5X does not apply.The Mo’s method is more suitable to describe the crystallization behavior of PA5X.The a values of PA510,PA512 and PA513 change little with the crystallinity.Through the comparison of F（T）value,the relation of crystallization rate is PA513<PA510<PA512.The activation energy of non-isothermal crystallizationΔE is-144.09 KJ/mol,-216.79 KJ/mol,-160.60 KJ/mol respectively.