Preparation Of Liquid Crystalline Polyurethane And Its Molecular Compounding With Special Engineering Plastics(3D Printing Materials)

In this project,liquid crystal polyurethanes(LCPU)with molecular chain structures similar to special engineering plastics were synthesized through molecular chain design,and then combined with the composite characteristics of traditional thermotropic main chain liquid crystal polymer and thermoplastic plastic,in-situ molecular compound of LCPU and special engineering plastic poly(ether ether ketone)(PEEK)was prepared.(1)By synthesizing different polyurethane materials with the same mesogenic element(aryl ether ketone structure),the effect of the type of isocyanate on the liquid crystallinity of the material was explored.The results show that the polyurethane materials synthesized with different isocyanates have good mesogenic properties,and they have a great influence on the glass transition temperature and the initial melting temperature and has no effect on the isotropic temperature of the material.The isotropic temperature mainly depends on the rigid mesogen.(2)By synthesizing polyurethane materials with different mesogens(biphenyl aryl ether ketone structure,aryl ether sulfone ketone structure,bisphenol A aryl ether ketone structure),the effect of rigid mesogens on the liquid crystallinity of the material was found.The results show that: polyurethanes containing biphenyl type aryl ether ketone structure and aryl ether sulfone ketone structure have good mesogenic properties.However,bisphenol A type aryl ether ketone polyurethanes show weak mesomorphism.(3)The liquid crystalline polyurethane containing aryl ether ketone structure with good liquid crystallinity was selected for in-situ molecular recombination with poly(ether ether ketone)by extrusion injection,and the corresponding characterization was carried out.The results show that: LCPU is fibrillated in situ and uniformly dispersed in the PEEK matrix;the introduction of LCPU improved the mechanical strength of PEEK.When the addition of LCPU was 6wt%,the tensile strength reaches 107.8 MPa,31.0% higher than 82.3 MPa of pure PEEK,and the bending strength reaches 140.1 MPa,17.5% higher than 119.2 MPa of pure PEEK.Rheological tests show that the addition of LCPU lowers the viscosity of PEEK and significantly improves the processing performance of PEEK.LCPU/PEEK molecular composite material overcomes the difficulty of processing after the composite of traditional fiber material and special engineering plastics.The decrease of processing viscosity can effectively solve the problem of increasing porosity caused by 3D printing,and can significantly improve the interlayer adhesion in the process of 3D printing.The interface between LCPU and PEEK has good compatibility.At the same time,the continuous reinforcement effect of LCPU can significantly improve the mechanical properties of materials,and can improve the mobility of 3D printing.