One-Step Synthesis and Properties of P4HB Based Thermoplastic Polyurethane Elastomers
A series of depolymerizable and recyclable thermoplastic polyurethanes(TPU)were synthesized through a one-step method using poly(4-hydroxybutyrate)(P4HB)as the soft segment and different diisocyanates and 1,4-butanediol(BDO)as the hard segment.The effects of feed ratio,P4HB molecular weight,chain extender content,and isocyanates on the properties of P4HB based TPU(P4HB-TPU)were studied,and the controllable depolymerization and monomer recovery of P4HB-TPU were also investigated.The thermal properties,mechanical properties,and thermal decomposition recovery of P4HB-TPU were studied using Fourier transform infrared spectroscopy,thermogravimetric analysis,differential scanning calorimetry,uniaxial mechanical stretching,and other testing methods to illustrate the relationship between polyurethane structure and properties.Results show that when n(—NCO)/n(—OH)is 1.1,tensile strength of P4HB-TPU can reach 37.8 MPa with comparable mechanical performance to commercial TPU.With the increase of molecular weight,the P4HB segment starts to crystallize and thus causes a transition of P4HB-TPU from elastic to plastic polyurethane.The increase of BDO content can improve the mechanical properties of P4HB-TPU to a certain extent,and use of cyclic symmetric isocyanates can effectively improve the tensile strength of materials.Notably,P4HB-TPU can use Sn(Oct)2 at 170℃,200 Pa that be depolymerized intoγ-BL monomer,and achieves a monomer recovery rate of approximately 98%.
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