Synthesis and Properties of Bio-based Polyurethane Based on Polylactide Diol
Ploylactate(PLA)diols with Mw 1 500 were synthesized by esterification using lactic acid(L-LA)as monomer,reacting with 1,4-butanediol(BDO),1,6-hexanediol(HDO)and 1,12-dodecanediol(DCO)respectively.The structure of PLA diols were analyzed by Fourier transform infrared spectroscopy(FT-IR)and nuclear magnetic resonance(1 H-NMR).The hydroxyl and acid values were determined by automatic potentiometric titrator.A series of polylactate polyurethanes were synthesized by solution method using PLA diol as soft segment,hexamethylene diisocyanate(HDI)and chain extender BDO as hard segment.The structure and properties of the polyurethanes were characterized by FT-IR,gel permeation chromatography(GPC),differential scanning calorimetry(DSC),thermogravimetric analysis(TG)and tensile test.The results showed that,with the increase of the carbon chain length of the three alkylene diols used in the synthesis of PLA diol,the melting point of polylactate polyurethane decreased from 118℃ to 103℃,the glass transition temperature decreased from 8℃ to-8℃,the elongation at break increased from 154%to 211%.The tensile strength(around 8 MPa),modulus and Shore hardness of the polylactate polyurethane gradually decreased.
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