Synthesis,structure And Properties Of Semi-aromatic Polyamide PA10T/10I-PEG Thermoplastic Elastomer

Thermoplastic elastomer（TPE）is a new type of polymer material.Due to its excellent properties and recyclability,TPE has received extensive attention in the past 30 years and has been applied in many fields.Polyamide thermoplastic elastomer（TPAE）is a new member of TPE,which has excellent wear resistance,high elasticity,chemical corrosion resistance and low temperature toughness.Therefore,TPAE has been widely used in automotive,medical,sports equipment and other fields.However,the hard segment of the commercial TPAE materials is mostly composed of aliphatic polyamide,which cannot meet the requirements of applications in harsh environment,such as aeronautics,military,chemical process fields.Hence,the development of a new type of TPAE material with excellent high temperature performance is of great significance for solving the shortcomings,and broadening the application range of TPAE.Compared with aliphatic polyamides,semi-aromatic polyamides have a rigid benzene ring structure in the main chain.It has high glass transition temperature,melting point and heat distortion temperature.It can be used to synthesize TPAE to improve the heat resistance.Considering that the TPAE polymerization temperature should not be too high,it is necessary to adjust the melting point of semi-aromatic polyamide as the hard segment of TPAE.Based on the above analysis,we select poly（decamethylene terephthalamide/decamethylene isophthalamide）（PA10T/10I）as the hard segment and polyethylene glycol（PEG）as the soft segment to prepard TPAE.This thesis mainly carries out research work from the following aspects: 1)A series of PA10T/10 I with different melting points are prepared by a solid-phase polycondensation method;2)Using PA10T/10 I as the hard segment and PEG as the soft segment to synthesize TPAE with different thermal and mechanical properties by a two-step method;3)The feasibility of one-pot synthesis of PA10T/10I-PEG elastomers is explored,and the elastomers with different ratios of soft and hard segments are synthesized by this method,the crystallization kinetics of elastomers is analyzed;4)Optimizing and amplifying the one-pot synthesis process;5)Graphene oxide/ semi-aromatic polyamide thermoplastic elastomer composites are prepared by in-situ polymerization to improve the mechanical properties.The main research results are listed as follows:1.Preparation of semi-aromatic polyamide PA10T/10 I copolymer by solidphase polycondensation（1）PA10T,PA10I and copolymer PA10T/10I are successfully synthesized by solid-phase polycondensation method.The test results show that the intrinsic viscosity of the resultant polymer range from 1.053-1.218 d L/g,and the content of 10 I in PA10T/10 I is consistent with the monomer feed ratio.（2）Due to the asymmetry of 10 I unit,the melting point of 10 T is reduced.As the content of 10 I increase,melting point of the polymer decreases from 307.9 ℃ to 230.5 ℃,and glass transition temperature decreases from 141.1 ℃ to 105.9 ℃.When the copolymer become amorphous,tensile strength and tensile modulus decrease rapidly.2.Synthesis of PA10T/10I-PEG thermoplastic elastomer by two-step method（1）We use PA10T/10 I as the hard segment and PEG-1000 as the soft segment,to prepard PA10T/10I-PEG elastomer by a two-step method.By this method,a series of PA10T/10I-PEG elastomers with different hard segment copolymerization ratios are successfully synthesized.（2）The copolymerization ratio of the hard segment has a significant impact on the mechanical and thermal properties of PA10T/10I-PEG elastomers.With the increase of the 10 I content,the glass transition temperature of the hard segment drops from 59 to 30 ℃.The mechanical properties of PA10T/10 IPEG elastomer can be adjusted by the copolymerization ratio of the hard segment.With the increase of 10 I content,the elongation at break decreases from 470 % to 833 %,and the tensile strength decreases from 40.0 MPa to 7.1 MPa.（3）The high temperature tensile tests of TPAE-4 and Pebax^R 5533 show that PA10T/10I-PEG elastomer maintains better mechanical properties at high temperature state.The stress of TPAE-4 only show rapid attenuation at 80 ℃,which is much higher than Pebax^R 5533（50 ℃）.It is fully explained that PA10T/10I-PEG thermoplastic elastomer has excellent mechanical properties at high temperature.3.Synthesis of PA10T/10I-PEG thermoplastic elastomer by one-pot method and analysis of non-isothermal crystallization kinetics（1）PA10T/10I-PEG thermoplastic elastomer is prepared creatively by one-pot method of putting raw materials into reaction kettle for polymerization.Comparing the samples synthesized by these two methods,it is found that the samples had similar intrinsic viscosity,crystallization temperature,melting temperature,and mechanical properties,indicating that the one-pot method can be used to synthesize PA10T/10I-PEG elastomer.（2）PA10T/10I-PEG elastomers with different hard-segment molecular weights are synthesized by one-pot method.The properties of the elastomer can be effectively changed by different ratio of the hard segment in elastomer: with the decrease of the proportion of the hard segment in the elastomer,the crystallinity,melting point and melting enthalpy gradually decrease,while the elongation at break gradually increases from 494.8 % to 898.8 %,and the tensile strength gradually decreases from 41.1 MPa to 21.9 MPa.（3）Avrami’s equation and Mo’s method are employed to investigate non-isothermal crystallization kinetics of TPAEs and PA10T/10 I.These two methods present similar results that as the molecular weight of hard segments increase,the halftimes of non-isothermal crystallization decrease,and the crystallization rate follow the order of TPAE-2000> TPAE-1500> PA10T/10I> TPAE-1000.Then the crystallization activation energies of TPAE-1000,TPAE-1500,TPAE-2000 and PA10T/10 I are calculated by Kissinger and Friedman methods.The values are-13.9 KJ/mol,-22.3 KJ/mol,-22.9 KJ/mol,and-17.9 KJ/mol,respectively.And the crystallization activation energy decreases as the increase of relative crystallinity.It can be seen that the nonisothermal crystallization behavior of TPAE changes with the molecular weight of the hard segment.4.optimization and synthesis amplification of one-pot method,and application research of elastomer toughening（1）To improve the synthesis efficiency,the one-pot synthesis process is optimized.We use orthogonal test method in the pre-polymerization process to investigate the effects of pre-polymerization temperature,time,catalyst amount,and stirring speed on the molecular weight of the polymer.We also evaluate the effect of various catalysts,and screen the best one.In the postpolymerization process,the factors as polymerization temperature,polymerization time,catalyst amount,vacuum degree and stirring speed are analyzed.As result,the viscosity of the elastomer which is synthesised by the optimal process is increased to 1.248 d L/g,higher than previous experiments,and the reaction time is shortened.（2）A new 5L reaction kettle has been designed to synthesis three kinds of elastomers with hard segment molecular weight of 1000,1500 and 2000 g/mol by using the optimal synthesis process.With this new reactor,about 1000 g of materials can be prepared each time,which is far more than the previous output.The sample prepared by new reactor maintains a high intrinsic viscosity,and have similar mechanical properties.（3）Compared with the commercial elastomer Pebax^R 5533,E-1000 has higher Vicat softening point（134.1℃）.At room temperature,E-1000 has similar mechanical properties with the commercial Pebax^R 5533.However,at high temperature,the mechanical property retention of E-1000 is better,and the turning point of its flexural modulus is 100℃,which is much better than that of Pebax^R 5533（70 ℃）.（4）E-1000 is used as a toughening agent to toughen PA6T/66 glass fiber composites.Compared with Pebax^R 5533 and POE-g-MAH toughening agents,the mechanical properties and toughening effect of E-1000 toughened composites are better.When the addition amount of E-1000 reaches 8wt%,the notched impact strength of the composite material reaches 17.197KJ/m2,which is much higher than that of the commercial toughening agent.5.Preparation of graphene oxide PA10T/10I-PEG elastomer composite by insitu polymerization（1）Graphene oxide/elastomer composites are prepared by in-situ polymerization with two kinds of filler addition methods.The results show that graphene oxide in the samples prepared by the GO-H method,can be exfoliated into a monolithic state.The surface of the graphene is grafted with hard segment molecular chains,while the graphene prepared by the GO-S method show obvious agglomeration.The tensile test shows that the mechanical properties of composites prepared by GO-H method are better.（2）The tensile strength of GO-H 0.2 can reach 24.5 MPa.In addition,the surface of the filler can absorb the free hard segment and form a "spherical" structure to reduce the interface friction between the filler and the soft segment.After that,the elongation at break of the material is improved up to 952.4 %.The high temperature tensile test results show that after adding graphene oxide,mechanical properties of elastomer under high temperature state are better maintained.