STUDIES ON DAMPING PROPERTIES OF POLYURETHANE/VINYL ESTER RESIN COMPOSITE ELASTOMER
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A series of polyurethane/vinyl ester resin (PU/VER) composite elastomers were prepared by precursors polymerization. The damping properties of PU/VER samples, with different composition, different isocyanate index and hydroxyl groups in VER metered or not, were studied by dynamic mechanical analysis (DMA). The results demonstrated that PU/VER composite elastomers show better damping properties at PU/VER=60/40 and isocyanate index at close range 1. When hydroxyl groups in VER were not metered, the elastomers presented two glass-transition temperatures. Furthermore, the damping temperature range of PU/VER cross-linking copolymer with better tan δ within normal temperature range was beyond 100 ℃, when VER acted as cross-linking agent of PU.Keywords:
Isocyanate
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4,4'-diphenylmethane diisocyanate(MDI)and polyethylene glycol(PEG)were used as raw materials for synthesis of isocyanate terminated polyurethane(PU)pre-polymer.Then,PU pre-polymer was used to graft trifunctional epoxy resin(TEP)which was synthesis in lab to obtain cross-link TEP-PU.Fourier Transform Infrared spectroscopic analysis(FT-IR),Scanning Electron Microscope(SEM),Thermogravimetric analysis(TG)and Dynamic Analysis of thermodynamics(DMA)were used to study postcured of TEP-PU groups changing,morphology thermal properties and dynamic mechanical properties respectively.Results indicated that PU chain grafted onto the TEP chain successfully.When m(PU)∶m(TEP)was 5%,the Barcol hardness was 41.4HBa,impact strength was 23.32kJ/m2,glass transition temperature was obviously improved,section of modified TEP presented ductile fracture.
Thermogravimetric analysis
Isocyanate
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Polyurethane elastomer was synthesized with diphenylmethane diisocyanate and poly e-caprolactone glycol/PEPA using 2-hydroxypropyl(2-hydroxyethyl) carbamate(HPHEC) or 1,4-butanediol as a chain extender,The product was characterized using differential scanning calorimeter(DSC),dynamic mechanical analyzer(DMA),electronic universal testing machine,and rubber resilience tester.It showed that gel time of polyurethane elastomer based on HPHEC was 3 times that of based on 1,4-butanediol.Tear strength of polyurethane elastomer based on HPHEC increased 10 %~ 25 %,and the glass transition temperature(Tg) and dynamic loss tangent(tanδ) also increased.
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First a hydroxy-terminated unsaturated polyester with low average degree of polymerization(UP)was synthesized by molecular design and then a block copolymerization modified unsaturated polyester resin with isocyanate was preparead by the copolymerization of UP and isocyanate(PU).The changes of molecular functional groups at all stages of UP /PU copolymer synthsis,effect of alcohol /acid molar ratio and diol types on the average degree of polymerization and viscosity of UP oligomer,effec of PU chains in the UP /PU copolymer on the mechanical properties of cured resin and the properties of the glass fiber compisite were investigated by the mechanincal property tests and IR analysis.The results showed that the tensile strength of UP /PU casting and glass fiber compisite were 75 MPa,956 MPa and the flexural strength were 116 MPa and 1220 MPa respectively.The existing defects of high brittleness and curing shrinkage rate and poor adhesion to glass fiber of unsaturated polyester resins were improved by UP /PU copolymerization.
Isocyanate
Shrinkage
Degree of polymerization
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Isocyanate-terminated polyurethane was synthesized with polyethylene glycol and toluene disocyantes,which was used to modify the epoxy resin.Chose D-230 as hardener to produce the PU/EP composite.Mechanical properties of the epoxy resin with different PU contents were studied,and the epoxy resin was also characterized by FTIR.Additionally,damping properties of the PU/EP composite were investigated using DMA,and the results showed that the damping properties of EP was evidently improved by blending with PU,and with the testing frequency increased,the spectra of tanδ-T shifted to higher temperature.
Isocyanate
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Modified polyether polyurethane and its film were prepared from prepolymer of amino-terminal non-isocyanate polyurethane and prepolymer of polyether-based polyurethane via block copolymerization.Synthesis condition of non-isocyanate prepolymer was analyzed;The impact of film-forming temperature and value of NCO and NH2 ratio on mechanical properties of membrane were investigated;Mechanical properties of different polyurethane materials were compared;Degree of phase separation was studied using differential scanning calorimetry(DSC).It showed that carbamate group was introduced into the amino-terminal non-isocyanate prepolymer;The best film-forming temperature was 140 ℃;When NCO/NH2 of prepolymer was 1/0.9,the best performance was obtained,tensile strength of 25.1 MPa,modulus of 100 % elongation of 5 MPa.Compared with regular polyurethane,polyurethane block with amino-terminal non-isocyanate polyurethane prepolymer had higher mechanical properties;DSC curves showed two different glass transition temperatures indicating phase separation.
Prepolymer
Isocyanate
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The emulsion of waterborne polyurethane /PA was prepared with isophorone diisocyanate,PTMEG,acrylate monomer as main material,trimethylolpropane and self-made hyperbranched polyurethane as cross-linking agent.Ther-mogravimetric analysis(TGA) and dynamic mechanical analysis(DMA) results showed that the heat resistance of polymers with two different cross-linking agents was little difference,and the damping properties was good when damping factor tanδ was about 0.75,the temperature range of tanδ greater than 0.3 was about 60℃.And the damping properties was better with the increasing contents of PA.
Trimethylolpropane
Isophorone diisocyanate
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The reaction rate of NCO groups by producing polyurethane/epoxy resin IPN foams was faster than that by producing pure PU foam, which was attributed to that the curing agents of epoxy resin were also acted as the catalysts for the reaction of NCO groups. The epoxy groups, however, show lower reaction rate and conversion by producing IPN foams than that by producing pure epoxy resin. The reason might be owed to that the epoxy groups are diluted and restricted by the PU network. There are three kinds of reactions between the PU and EP networks: the reaction between the OH groups formed by ring opening of epoxy groups with NCO groups, the reaction between the OH groups on polyol and epoxy groups and the reaction between the NCO groups and epoxy groups to form oxazolidinone. Because of high degree of crosslinking in PU/EP IPN rigid foams and chemical bonds between the PU and EP networks, the PU and EP resin are miscible. Only one glass transitions temperature ( Tg ) was observed in PU/EP IPN rigid foam by dynamic mechanical thermal analysis (DMTA). There is no obvious interphase surface between the PU and epoxy resin observed in IPN foams with transmission electron microscopy (TEM).
Interpenetrating polymer network
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Isocyanate-terminated polyurethane was synthesized from polyethylene glycol and toluene disocyantes, which was used to modify the epoxy resin. D-230 was chosen as hardener to produce the PU/EP composite. The structure of composite was characterized by FTIR spectrum. Mechanical properties of the epoxy resin with different PU content were studied. Additionally, damping properties of the PU/EP composite were investigated using DMA, and the results showed that the damping properties of EP evidently improved by blending with PU and with the testing frequency increased, the spectra of tanδ-T shifted to higher temperature.
Isocyanate
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Abstract Phenolic hydroxyl‐terminated (HTPU) and aromatic amine‐terminated (ATPU) PU modifiers were prepared by reacting two different macroglycols (PTMG, polytetramethylene glycol, M n = 2000, and PBA, Polybutylene adpate, M n = 2000) with 4,4′‐diphenylmethane diisocyanate (MDI), then further coupling with two different coupling agents, bisphenol A or 4,4′‐diaminodiphenyl sulfone (DDS). These four types of PU prepolymers were used to modify the epoxy resin with 4,4′‐diamino‐diphenyl sulfone as a curing agent. From the experimental results, it was shown that the values of fracture energy, G IC , for PU‐modified epoxy were dependent on the macroglycols and the coupling agents. Scanning electron microscopy (SEM) revealed that the ether type (PTMG) of PU‐modified epoxy showed the presence of an aggregated separated phase, which varied between 0.5 μm and 4 μm in the ATPU (PTMG) and between 1 μm and 1.5 μm in HTPU (PTMG) modified system. On the contrary, the ester type (PBA) PU‐modified epoxy resin showed a homogeneous morphology and consequently a much smaller effect on toughening for its good compatibility with the epoxy network. In addition, it was found that the hydroxyl‐terminated bisphenol A as a coupling agent improved fracture toughness more than the amine‐terminated DDS because of effective molecular weight buildup by a chain extension reaction. The glass transition temperature ( T g ) of modified epoxy resin as measured by dynamic mechanical analysis (DMA) was lower in PTMG‐based PU than in a PBA‐based PU series with the same weight of modifier.
Diglycidyl ether
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Polyurethane prepolymer with isocyanate-terminated was prepared by PPG and toluene diisocyanante(TDI),then epoxy-terminated polyurethane-epoxy resin were prepared by polyurethane prepolymer and epoxy resin,and curing with low-molecular polyamide.Different tensile strength and hardness was obtained by changing NCO/OH or PPG3031/2020 of polyurethane prepolymer.The result showed that the tensile strength and hardness enhanced with the increase of PPG3031/2020 or NCO/OH in polyurethane prepolymer.
Prepolymer
Toluene diisocyanate
Isocyanate
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