Synthesis,Structure-property Of (Co) Polyesters Based On Bio-based 1,5-pentanediol

1,5-Pentanediol(PeDO)is an important feedstock for polyesters,unsaturated polyesters,polyurethane and fine chemicals,which can be used in plastics,fibers,elastomers,coatings and adhesives.Throughout the ages,PeDO is produced from petroleum feedstock.However,its production and applications are still in small scale because of limited raw materials,complex process and high cost.PeDO can also be synthesized from biomass through furfural,an important industrialized biobased compound.With the great progress in synthetic technology in furfural and PeDO in the recent decade,bio-based PeDO will be industrially produced from furfural at economical scale and low cost in the foreseeable future.As PeDO is an odd-carbon diol monomer,(co)polyesters based on PeDO may have some specific thermo-mechanical properties different from existing ones.However,researches on PeDO-based(co)polyesters are still very limited.Systematic study is still lacked,and there appear no(co)polyesters with satisfactory performance and practicability in the literatures.In this paper,a series of high molecular weight(co)polyesters were synthesized through esterification-polycondensation reaction using PeDO,C4-C12 aliphatic dicarboxylic acids and terephthalic acid as monomers.A systematic structure-performance study of PeDO-based(co)polyesters was conducted to provide reliable basic data and technical support for further R&D.1.High molecular weight aliphatic polyesters were synthesized from biobased PeDO and aliphatic diacids with 4,5,6,9,10 or 12 carbon atoms via melt polycondensation.The effects of dicarboxylate chain length on crystalline structure and thermo-mechanical properties were investigated.All the polyesters had weight-average molecular weight over 100 000 g/mol or intrinsic viscosity over 1.05 dL/g except poly(1,5-pentylene adipate)(PPeA)which was less thermally stable than others.As semi-crystalline polymers,they have polyethylene-like crystal structure and crystallize rapidly except poly(1,5-pentylene succinate)(PPeS).As a whole,the crystallizability and melting temperature(Tm)increase with dicarboxylate chain length,and "even-odd" effect exists to certain extent.Among them,poly(1,5-pentylene azelate)(PPeAz),poly(1,5-pentylene sebacate)(PPeSe)and poly(1,5-pentylene dodecanedioate)(PPeDo)have Tm of 50-62 ?,good thermal stability and exhibit comparable or even superior tensile properties in comparison with polyethylene and the well-known biodegradable copolyester,poly(butylene adipate-co-terephthalate)(PBAT).These bio-based and potentially biodegradable polyesters appear to be promising materials for practical applications.2.PPeT with intrinsic viscosity of 0.75 dL/g was synthesized from biobased PeDO and terephthalic acid(TPA)via melt polycondensation.PPeT is opaque semi-crystalline polymer with a melting point of 132 ?(equilibrium melting point is 147 ?).PPeT prones to cold crystallization and its melting point and crystallization ability is poorer than other TPA-based polyesters.After eliminating the heat history,the melt-crystallization enthalpy is 4.1 J/g and crystallinity is 2.3%at cooling rate of 10 ?/min.The crystallization half time is still up to 8 min at the fastest melt crystallization temperature of 75 ?.PPeT has a wide self-nucleation temperature range(160-200 ?),to fully eliminate its thermal history,the isothermal temperature of 200 ? for 5 min is needed.The slow nucleation may be the reason for slow crystallization rate.PPeT is more stable than aliphatic polyester.PPeT performs as typical flexible crystalline plastics,it has tensile modulus of 650 ± 60 MPa,breaking strength of 21 ± 1 MPa and elongation at break and 450 ± 30%.3.PPeST with intrinsic viscosity among 0.78-1.4 dL/g and PPeAT with intrinsic viscosity among 0.58-0.66 dL/g were synthesized from bio-based PeDO,succinic acid(or adipic acid)and TPA via melt polycondensation.The effects of TPA content on chemical structures and thermo-mechanical properties were investigated.With increased TPA content,glass transition temperature(Tg)increases,Tm and the crystallizability first decrease and then increase.The mechanical properties of copolyesters are relatively poor,but considering excellent chain flexibility,they are expected to be used as impact modifiers for brittle polymeric materials.