Preparation and properties of bio-based degradable thermoplastic polyurethanes based on imine-bonded vanillin aldehyde diol
Traditional thermoplastic polyurethane(TPU)relying on petrochemical sources is facing significant challenges in both industrial production sustainability and the recycling of waste after use due to resource scarcity and environmental protection requirements.Developing bio-based TPU synthesized from renewable biomass resources is becoming more urgent.A renewable biomass resource,vanillin aldehyde(VAN),was reacted with m-xylylenediamine to synthesize a bio-based chain extender VAN derived diol(VAN-OH)with an imine bond in its molecular structure,which was then blended with 1,4-butanediol(BDO)to form chain extender components with different proportions of VAN-OH and BDO.A degradable bio-based TPU(BTPUs)with high performances were prepared by a two-step addition polymerization with the chain extender components,polycaprolactone diol(PCL)and 4,4'-diphenylmethane diisocyanate(MDI).The structure,thermal properties,mechanical properties and chemical degra-dation performance of BTPUs were tested and characterized.The results show that the moderate addition of the bio-based chain extender VAN-OH enhances the hydrogen bonding in the molecular chain structure of BTPUs,the crystallization properties,and the degree of microphase separation,which increases the thermal stability,mechanical and degradable properties of BTPUs.When the mass fraction of VAN-OH in the chain extender components is 25%,the mechanical properties of BTPUs are the best,with tensile strength of 33.32 MPa and elongation at break of 823.62%,and the degradation time is 37.5%shorter compared to that of the BTPUs without VAN-OH.When the mass fraction of VAN-OH in the chain extender components is more than 50%,the mechanical properties of BTPUs decrease significantly,but the degradation time is further shortened.The above results verify that the presence of a dynamic imine-bonded biobased chain extender can improve the thermal,mechanical and degradation properties of TPU,and providing valuable reference for developing and research of BTPUs.
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