Regulation Of Micro-Phase Separation Morphology,Properties And Applications Of Polyurethane

Theory and application researches of polyurethane?PU?have been widely concerned because of the excellent performance such as abrasion resistance,low temperature flexibility,high strength,strong adhesion,chemical resistance.The outstanding performance of PU is depending on its unique micro-separation structure.The incompatible of rigid phase and soft phase causes the micro-phase separation morphology of PU.The hard segments can interact with each other by hydrogen bond interactions and aggregate into the rigid phase,the soft segments are forming the independent soft phase.Hydrogen bonds are abundant in PU and significance to the micro-phase separation morphology.It is an effective way to achieve a better performance for PU by designing hydrogen bonds and adjusting the micro-phase separation morphology.As a different form of PU,waterborne polyurethane?WPU?is environment-friendly,non-toxic,no-pollution and has been widely used and researched.The design of micro-phase separation morphology of WPU is the necessary method to achieve good performance.In this work,the micro-phase separation morphology of PU has been designed and the effects of micro-phase separation morphology on the properties of PU have been studied.The relationship between micro-phase separation morphology of PU and its performance and applications have been considered.Based on polyethylene-1,4-cyclohexynol-terephthalate glycol?PETG?as macromolecular diols,a series of waterborne polyurethane-ureas?WPU?have been synthesized.The effects of PETG on micro-phase morphology and hydrogen bond interactions of WPU have been investigated.The chemical structure of synthesized WPU was examined by Fourier transform infrared spectroscopy?FT-IR?and nuclear magnetic resonance spectroscopy?¹H NMR?.The effects of PETG on the morphology of the WPU have been studied by changing the PETG content and the initial ratio of isocyanate and hydroxyl(n?NCO?/n_{?OH,polyester?}).The micro-phase morphology of the WPU have been examined by transmission electron microscope?TEM?,X-ray diffraction tests?XRD?,dynamic mechanical analysis?DMA?and differential scanning calorimetry?DSC?as well as the deconvolution of amino and carbonyl stretching region in FT-IR curves.The results showed that PETG chains were aggregated into uniform nano morphology and dispersed in the hard domains which were hydrogen bonded with-NH.With the increased PETG content,PETG in WPU presented fibrous micro-structure,the hydrogen bond interaction among hard segments and the degree of micro-phase separation of WPU were decreased.However the increased hydrogen bonding index?HBI?indicated the hydrogen bond interaction between PETG and hard segments were increased.The independent micro-phase morphology of PETG enhanced the tensile strength,the hardness as well as the thermal stability of WPU films significantly.Macromolecular diols with different carbamate content were synthesized by alterative ratio of n_?PPG?/n_?HMDI?.The molecular weights of these macromolecular diols were measured by gel permeation chromatography?GPC?.In addition,based on these macromolecular diols,waterborne polyurethanes?WPU?were prepared by the pre-polymerization method.The structure and molecular weight of the WPU were characterized by nuclear magnetic resonance spectroscopy?H NMR?,Fourier transform infrared spectroscopy?FT-IR?and GPC respectively.When the mole ratio of n_?PPG?and n_?HMDI?decreased,the particle distribution of WPU became broader and the average particle size became larger.Furthermore,the hydrogen bonding interaction in WPU films were analyzed by the deconvolution of amino,carbonyl band and ether band of FT-IR spectra.The results showed that when introduction of carbamate into the macromolecular diol,the ordered hydrogen bonding interaction in hard segments increased and the interaction between carbamate and ether occurred.The increased hydrogen bonding interaction leaded to the higher micro-phase separation which confirmed by atomic force microscope?AFM?and differential scanning calorimetry?DSC?test.Carbamate in soft segments can significantly increase the modulus of WPU in the whole temperature range.Meanwhile,the tensile strength and the elongation at break were obvious increased when introduced carbamate into the soft segments because of the crossl inked structure and micro-phase separation morphology.The tensile strength of sample WPU1 caught 28.3 MPa which was 2.37 times and the elongation at break caught 910%which was 2.18 times than that of WPUO.According to the results in the last chapter,three different macromolecular diols were synthesized by the reaction of PBA and diisocyanate?isophorone diisocyanate?IPDI?,hexamethylene diisocyanate?HDI?and methylene-bis?4-cyclohexylisocyanate??HMDI??at the ratio of 2:1.Based on these macromolecular diols as soft segment,a series of waterborne polyurethane?WPU?adhesives were prepared.The structure and molecular weights of the WPU were characterized by nuclear magnetic resonance spectroscopy?¹H NMR?,Fourier transform infrared spectroscopy?FT-IR?and gel permeation chromatography?GPC?respectively.Furthermore,the hydrogen bonding interaction of WPU were analyzed by the deconvolution of amino,carbonyl band and ether band of FT-IR spectra.The results showed that the hydrogen bonded-NH was increased when carbamate was in the soft segment.The crystallinity of WPU was tested by X-ray diffraction tests?XRD?and differential scanning calorimetry?DSC?.The results showed that the crystallinity of WPU2?HDI?and WPU3?HMDI?were enhanced,especially for WPU2.Meanwhile,the glass transition temperature of soft segments(T_g,s)as well as the films mechanical strength,storage modulus,the contact angle and thermo-stability were increased with the introduced carbamate into soft segment.The T-peel tests of plasticized PVC/WPU/plasticized PVC joints and lap-shear tests of wood/WPU adhesive/wood joints were carried out.The results indicated that the carbamate in the soft segment could significantly enhance the adhesion of WPU at an appropriate activation temperature.Solid polymer electrolyte?SPE?membranes which composed of thermoplastic polyurethane?TPU?,poly?ethylene oxide??PEO?and lithium bis?trifluoromethane sulfonimide??LiTFSI?were prepared and investigated in this work.The results showed that the addition of TPU to the blend polymer resulted in loss of the crystallinity of PEO and improved the dissolution of lithium salts into the SPE matrix.TPU can significantly improve the mechanical stability and the electrochemical properties.However,the increased TPU introduction deceased the ionic conductivity of SPEs.Among the TPU/PEO blend electrolytes,the TPU/PEO = 1:3 based electrolyte presented the comprehensive performance which the tensile strength caught 1.38 MPa and the ionic conductivity caught 10^-4 S cm^-1 with electrochemical stability above 5 V?vs.Li⁺/Li?at 60 0C.The LiFePO4/SPE/Li coin cell based on SPE?TPU/PEO = 1:3?was assembled and showed an attractive discharge capacity(140 mAh g^-1 and 154 mAhg^-1 at 0.2 C under 60 ? and 80 ?,112 mAh g^-1 and 127 mAhg^-1 at 1 C under 60 ? and 80 ?)and outstanding cycling stability?close to 96%and 94%after 100th cycles at 1 C under 60 ? and 80 ??,respectively.These results demonstrated that the TPU/PEO blend polymer electrolyte should be a promising electrolyte for all-solid-state lithium ion batteries.