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In continuing efforts to understand urea phase connectivity in flexible polyurethane foams and its implications on physical properties, LiCl is used to alter the phase-separation behavior of slabstock foams. Comparisons are also drawn with plaque counterparts, which are prepared using the same polyol, isocyanate, and chain extender (water). LiCl is shown to alter the solid-state phase separation behavior...
Simultaneous small angle X-ray scattering (SAXS) and force measurements have been recorded during tensile deformation of two contrasting polyurethane elastomers. The elastomers comprise the same hard and soft chemical segments; in Sample A, the length of the hard blocks is randomised while in Sample B the hard blocks are monodisperse. During deformation of Sample A, the SAXS halo from the mesophase...
A new method of the synthesis of aliphatic polyurethanes from diamines and diols or alternatively from α,ω-aminoalcohols using ethylene carbonate as a substitute of phosgene is presented. It has been found that the transurethanisation reaction between α,ω-bis(2-hydroxyethoxycarbonylamino)alkanes and diols containing six or more carbon atoms in a molecule carried out in the presence of tin coordination...
A segmented polyurethaneurea based on poly(tetramethylene oxide)glycol, a cycloaliphatic diisocyanate and an unsymmetrical diamine were prepared. Urea content of the copolymer was 35wt%. Electrospinning behavior of this elastomeric polyurethaneurea copolymer in solution was studied. The effects of electrical field, temperature, conductivity and viscosity of the solution on the electrospinning process...
The synthesis of the new highly extended chromophore 2-[4-(N,N-dihydroxyethylaminophenylazo)-phenyl]benzoxazole is described. Two polymers obtained by the polycondensation of this chromophore with propyloxyterephthalic acid and 2,4-tolylenediisocyanate and one obtained by the polycondensation of 2-[4-N,N-bis(2-hydroxyethyl)aminophenyl]-6-nitro-benzoxazole with 2,4-tolylenediisocyanate have been prepared...
It was established that flexible polyurethane foams based on polyester or polyether polyol and toluene diisocyanate can be converted quantitatively into liquid form by treatment with triethyl phosphate (C 2 H 5 O) 3 P(O). Structures of the degraded products were studied by 1 H, 13 C and 31 P NMR spectroscopy. The degraded products are phosphorus...
Quenched systems corresponding to different reaction extents of polyurethane (PU) network formation have been studied using broadband dielectric spectroscopy in order to apprehend the evolution of α-relaxation during gel formation. Three PU systems based on poly(oxypropylene) triol of molar mass 260, 700 and 6000g/mol. have been investigated. While for the pure triols the distribution and temperature...
Interpenetrating polymer networks (IPNs) of 2-hydroxyethyl methacrylate terminated polyurethanes (HPU) and polyurethanes (PU) with different ether-type polyols were prepared by simultaneous solution polymerization. Differential scanning calorimetry showed that the compatibility of polymers in IPN formation depends on the molecular weight of the prepolymers. Compatible IPN systems resulted in greater-than-average...
The fracture toughness of a series of polyurethane elastomers based on polytetramethylene glycol (PTMEG) soft segment, a toluene diisocyanate (TDI) and a dimethyl-thio-toluenediamine (Ethacure E300) curative with different ratios of isocyanate to amine groups has been studied. The fracture toughness required to initiate crack growth was found to be invariant with stoichiometry but the degree of stable...
A series of segmented block copolymers of NR and 1,3-butanediol-toluene diisocyanate oligomers have been synthesized with varying hard segment content. The synthesis has been carried out by one-shot and two-shot processes in solution. The products were characterized by spectral analysis, thermal and mechanical analysis, SEM and optical microscopy. They are found to be amorphous materials having no...
Temperature-sensitive polyurethanes are obtained by reacting trifunctional isocyanate with poly(ethylene oxide)–b-poly(propylene oxide)–b-poly(ethylene oxide) [Pluronic L122]. The temperature-dependent interactions among poly(propylene oxide) [PPO] segments are observed by n.m.r. At low polyurethane concentrations, segment–segment PPO interactions within a given gel cluster are predominant, whereas...
The dependence of free volume on temperature has been monitored in some cross-linked polyurethanes, with different chain lengths, by using positron annihilation lifetime spectroscopy (PALS). The spectra were analysed in terms of continuous distributions in order to obtain the distribution of the longest component, τ 3 . The relative number and the mean size of free volume holes have been...
Annealing effects on ferroelectric properties of an aromatic polyurethane (m-xylene nonamethylene dicarbamate, PUMX-9) were studied. X-ray diffractometry showed that the crystallinity of PUMX-9 increased during annealing. Both quenched and annealed polyurethane samples showed a similar electric displacement (D) versus electric field (E) hysteresis loop. Furthermore, the remanent polarization obtained...
The photochemical behaviour of aliphatic-based poly(ester-urethanes) is investigated. Polymer samples are submitted to irradiation in the presence of oxygen in conditions of long wavelength irradiation (λ > 300 nm) or short wavelength irradiation (λ = 254 nm). The evolution of the structure of photooxidized polymers is monitored by FTi.r. analysis of thin samples and the different photoproducts...
New di- and polyisocyanates were synthesized from α-amino acids. The reaction route included the preparation of α-isocyanatoacyl chlorides from the corresponding amino acids and trichloromethyl chloroformate and their conversion into diisocyanato diesters by reaction with silylated alcohols. For comparison, 3-isocyanatopropanoyl chloride was also prepared by reaction of the O-silylated β-alanine...
The dynamic mechanical behaviour of fully cured soluble and insoluble polyurethanes from two poly(oxypropylene)triols and a diisocyanate with initial ratios r H = [OH][NCO] from 1.44 to 1.8 were investigated. The dynamic behaviour during the curing reactions of two samples with r H = 1 was also measured. From extraction experiments the critical ratios for gelation r cH ...
Polyurethanes of different compositions were synthesized by chain extending the prepolymer formed by the reaction of poly(tetramethylene oxide)glycol and tolylene diisocyanate with 3,4-dihydroxycinnamic acid. The polyurethanes were characterized using Fourier transform infra-red and Fourier transform nuclear magnetic resonance spectroscopies. The molecular weights of the polymers were determined...
The mechanical properties and fracture behaviour of polyurethanes with two hardness levels have been measured. The polyurethanes were based on polytetramethylene ether glycol (PTMEG) and toluene diisocyanate (TDI) and two different curatives, or chain extenders - methylene-bis-orthochloroaniline (MBOCA) and dimethylthiotoluene diamine (Ethacure E300). The polyurethanes made using MBOCA as the curative...
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