Synthesis And Properties Of A Series Of New Thermoplastic Polyester Elastomer

Thermoplastic polyester elastomers owning a great many of advantages such as wide range of operating temperature,oil resistance,weatherability,excedllent thermodynamic properties,etc.,have occupied an important position in the consumption market of thermoplastic elastomer.With the development of science and technology,new requirements for elastomers have been put forward in the traditional and novel industrial fields in recent decades,which also accelerate the synthesis and application of new elastomers.In this paper,developers tend to explore the relationships between the structure and properties of elastomers,microphase separation mechanism of Polyether ester elastomer and ensure the reason of microphase separation,adopting melt polymerization to prepare three types of elastomers with different structures based on 2.5-dimethyl furandicarboxylate(DMFD)and 1.4-cyclohexanedicarboxylic acid(CHDA).In recent years,the main research of polymer materials on polymer materials has gradually transferred to environmental-friendly polymer materials from traditional petroleum-based polymer materials,which means renewable raw materials would be substitutes for petrochemical raw materials and applied to the synthesis of polymer materials.2.5-furandicarboxylic acid dimethyl ester(DMFD),a bio-based derivative original primarily from biomass feedstocks,is the main raw material for the synthesis of bio-based polyesters.At present,the development of polyether ester elastomers(TPEEs)with bio-based polyester as the hard segment is at the initial stage and the thermodynamic properties of the artificial TPEEs have not reached the ideal state whose main reason is that the rigidity of the polyester hard segment is insufficient or the poor crystallized ability.As a result,the contents of the second and third chapters of this paper mainly overcome the shortcomings of hard segments of such elastomers.To slove this problem,introducing a rigid circular diol structure,it can obtain a copolyester named PCBDEF with the characteristics of higher T_g,rigid chain and amorphous.PCBDEF derived from bio-based 2,5-furandicarboxylic acid,2,2,4,4-Tetramethyl-1,3-cyclobutanediol(CBDO)and ethylene glycol(EG).Thus PCBDEF as hard segment,PTMG-1000 as soft segment,they formed an exciting amorphous thermoplastic elastomers PCBDEF-PTMG.Research showed vitrified microarea is the main factor to promote the microphase separation of elastomers during the thermodynamical immiscibility between PCBDEF and PTMG.Additionally,although the degree of microphase separation increases with the increasing of PTMG content.PCBDEF-30 PTMG showed similar mechanical properties to SBS elastomers,whose tensile modulus,tensile strength and elongation at break is 140 MPa,47 MPa,and 511%,respectively.PCBDEF-50 PTMG showed complete rubber behavior due to extremely low glass transition temperature.However,introducing PTMG soft segments,thermal stability of elastomer rapidly falling off.And elastomer had obvious creep behavior and stress relaxation property during to the weak interaction between the chains.Therefore,to improve the thermal stability and reduce the effect of relaxation,we considered that crystalline hard segment was introduced in elastomer,which increased the interaction between chains.So,in Chapter 3,a polyester named poly(neopentyl glycol 2,5-furandicarboxylate)was synthetized,which possessed spherulitic morphology.Compared with the biopolyesters that have been reported,the spherulite size of PNF was six times more than the latter,and PNF had an appropriate T_g(68 ℃)and T_m(200 ℃).PNF had been proved to be a promising hard segment for the development of novel bio-based thermoplastic poly(etherester)elastomer(TPEE).By adjusting the PTMG soft segment from 40 to 70 wt%,PNFPTMG has tensile modulus,and elongation at break ranging from 192 to 17 MPa,and 600% to 1300%,respectively,with tensile strength remaining constant at around 37 MPa.More importantly,the shape recovery ratios increase from 57 to 90% at 200% strain when the amount of PTMG increases from 50 to 70 wt%,indicating excellent elastic property.Compared with the PCBDEF-PTMG elastomer,PNF-PTMG had week creep behavior and stress relaxation property.But the thermal stability of PNF-PTMG decreased by 20 ℃.In fact,it is not ideal to introduce PTMG soft segments into a thermoplastic polymer chain because it always inevitably brings about a decrease in thermal and tensile properties of the thermoplastic polymer.This inspires us to create a novel strategy to synthesize soft segment free TPEs by releasing the intrinsic elasticity of polymer chains.So,in Chapter 4,we design a series of polyesters from CHDA and diols with different side chains.The different side chains would result in different flexibility of the polymer chain and different steric hindrance on the ring structure during its conformational transition process.The elastomers,which contains cyclohexane ring,showed high elastic behavior by releasing entropy elasticity of polymer segments.The conformational transformation of cyclohexane ring has great influence on microstructure and macroscopical properties of polymer.Besides the stereochemistry,another important factor that could strongly affect the conformational transition of the cyclohexylene ring is the flexibility and steric hindrance of the neighboring unit connecting to the ring.Research showed that further incorporation of long side chain has weak effect on the coupled motion of the neighboring unit with the cyclohexylene ring,and thus reduces the polymer crystallization and increases flexibility of the chain(lower T_g),so the polymers’ behavior like thermoplastic elastomer(eg.PMPC).Meanwhile,TGA showed that the thermal stability of PMPC is higher than PCBDEFPTMG and PNF-PTMG elastomers,which is 20~40 ℃ higher than latter.