Thermoplastic Polyurethane Elastomers : Synthesis, and Study of Effective Structural Parameters (original) (raw)
Related papers
Polymer International, 1993
Polyester polyols from renewable resources have gained significant interest in the field of polyurethane chemistry. Two sets of segmented TPUs were prepared from crystalline and amorphous azelate polyols, 4,4 0-methylenebis(phenyl isocyanate), and 1,4-butanediol as a chain extender at a mole ratio of 1:2:1, respectively. Bio-1,3-propanediol (1,3-PDO) and 1,5-pentanediol (PTDO) were used to prepare crystalline azelate polyols, while 1,2-propanediol (1,2-PDO) and 2,2 0-dimethyl-1,3-propanediol (NPG) were used to prepare amorphous azelate polyols. All TPUs displayed clear glass transition temperatures (T g s) in between −36 and − 24 C, associated with azelate polyols soft segments, which are decreasing with increasing diols chain lengths in azelate polyols. TPUs based on crystalline azelate polyols exhibited higher mechanical properties and better heat resistance in comparison to their counter parts. Besides, TPU based on 1,3-PDO azelate showed lower percentage of hysteresis indicating lower heat build-up. This is essentially good for TPUs that are to be used in dynamic applications such as rollers and wheels. Hence, the study on structure-property correlation of the crystalline and amorphous azelate polyols and their effect on TPUs properties suggest that crystalline azelate polyols are suitable for dynamic application of TPU, and amorphous azelate polyols are suitable for coatings and adhesives applications.
Investigation of Thermoplastic Polyurethanes Synthesized via Two Different Prepolymers
Journal of Polymers and the Environment, 2019
The man aim of this work was to investigate the effect of the molecular weight of polyols, mixture of prepolymers, and [NCO]/[OH] molar ratio used during the prepolymer chain extending step on the chemical structure, thermomechanical and mechanical properties, and thermal stability of thermoplastic poly(ether-urethane)s In this work thermoplastic poly(etherurethane)s were synthesized by using polyols with a various molecular weight, 4,4′-diphenylmethane diisocyanate and biobased glycol. Materials were obtained by a two-step method. The tests were carried out for polyurethanes obtained from a mixture of prepolymers and for reference samples. In the case of materials obtained with using mixture of prepolymers, the ratio of both prepolymers was determined on 50/50 weight percent. Soft segments of materials prepared with using mixture consist of two different polyols. The chemical structure was analyzed using FTIR spectroscopy. The Gaussian deconvolution technique was used to study the hydrogen bonding as well as to decompose carbonyl region of three peaks in various TPUs. The thermal degradation behavior was investigated by using thermogravimetric analysis at heating rates of 10 °C/ min. It was confirmed that the mixture of prepolymers has an effect of the degree of phase separation, thermal stability and selected properties of synthesized thermoplastic poly(ether-urethane)s.
Development of polyurethane engineering thermoplastics. II. Structure and properties
Journal of Applied Polymer Science, 1993
Rigid, tough thermoplastic copolyurethanes were prepared by a prepolymer technique. The soft-segment content was varied over the 5-30 w t %. Six stoichiometric formulations based on diphenylmethane 4,4'-diisocyanate (MDI) , one or two different polyetherglycols, and one or two chain extenders of different structure were examined to test the possibilities of varying the degree of crystallinity of the products. Despite their thermoplastic characteristics, the resulting products were insoluble in the solvents normally used for elastomeric polyurethanes. The influence of curing temperature upon crystallinity and degree of polymerization was analyzed. Phase-structure analysis, performed by differential scanning calorimetry, dynamic-mechanical thermal analysis, and wide-angle X-ray scattering revealed complex phase structures strongly dependent on previous thermal history. In any case, the soft segments appear to constitute a dispersed phase in a rigid amorphous or semicrystalline matrix. Some samples exhibited two hard-segment glass transitions associated with the existence of a bimodal length hard-segment distribution. X-ray diffraction patterns suggested that more than one crystalline form was present in the crystalline phase. 0 1993 John Wiley & Sons, Inc.
Thermoplastic polyurethane elastomers based on aliphatic diisocyanates: thermal transitions
Polymer, 1977
A series of thermoplastic polyurethane elastomers based on polycarbonate diol, 4,4 0 -diphenylmethane diisocyanate and 1,4-butanediol was synthesized in bulk by two-step polymerization varying polycarbonate diol soft segment molecular weight and chemical structure, and also hard segment content, and their effects on the thermal and mechanical properties were investigated. Dynamic mechanical analysis termogravimetric analysis, differential scanning calorimetry, Fourier transform infrared-attenuated total reflection spectroscopy and mechanical tests were employed to characterize the polyurethanes. Thermal and mechanical properties are discussed from the viewpoint of microphase domain separation of hard and soft segments. On one hand, an increase in soft segment length, and on the other hand an increase in the hard segment content, i.e., hard segment molecular weight, was accompanied by an increase in the microphase separation degree, hard domain order and crystallinity, and stiffness. In phase separated systems more developed reinforcing hard domain structure is observed. These hard segment structures, in addition to the elastic nature of soft segment, provide enough physical crosslink sites to have elastomeric behavior. POLYM. ENG.
Journal of Applied Polymer Science, 2008
Two series of 4,4 0 -diphenylmethane diisocyanate (MDI) and poly(ethylene glycol adipate) (PEGA)-based polyurethane and polyurethaneurea elastomers were synthesized via a one-shot polymerization method and characterized using FTIR, 1 H NMR and 13 C NMR. The samples in the first series are extended by aliphatic diol chain extenders while in the second series mixtures of aliphatic diols and furanic or aromatic diamine chain extenders are used. TGA experiments revealed that with furanic or aromatic diamine chain extenders the polymer degradation temperature is shifted 90 C upwards, irrespective of the annealing time at 100 C according to ASTM 0573-99. The values of Young's modulus and of the tensile strength are higher and the strain at break is lower for the samples in series 2 compared to those in series 1. Increasing the annealing time at 100 C lowers Young's modulus. Dynamic mechanical thermal analyses points to a progressive microphase separation with annealing time.
Journal of Applied Polymer Science, 2008
The phase-separation behavior and morphology of polycarbonate-based polyurethanes were investigated as a function of the soft-segment molecular weight and chemical structure and the 4,4 0 -diphenylmethane diisocyanate/1,4-butanediol based hard-segment contents. Polarized optical microscopy and atomic force microscopy images showed that the surface morphologies changed as the soft-segment molecular weight and hard-segment content varied and also when the sample preparation conditions were modified. An increase in the soft-and hardsegment lengths led to increased phase separation with respect to the lower molecular weight soft segment, and this showed an interlocked and connected morphology of intermixed soft and hard domains. The surface morphol-ogy of phase-separated polyurethanes with hard segments composed of more than four to five 4,4 0 -diphenylmethane diisocyanate units contained globular hard-segment domains formed by spherulites, in which the size and connectivity between the branched lamellae changed with the hard-segment size. Interlamellar areas related to the soft segment were seen in the spherulites. Variations in the hard-segment spherulites were observed for polyurethanes based on soft segments of different molecular weights.
2008
A study was made of a family of polyurethane copolymers, in which the chemical components were: a hard segment (giving, on phase separation, hard nano-scale reinforcing particles); a soft segment (giving, on phase separation, an elastomeric matrix), and a diol chain extender. The chemical compositions of all three components were varied systematically and independently, and their mechanical responses were measured in cyclic tensile tests at room temperature, up to stretches in the range 5-6. Particular attention was paid to characterizing the inelastic features – hysteresis, and stress relaxation in interrupted tests – and their variations between the materials. The same materials were also studied by wide-angle X-ray scattering (WAXS), to determine levels of crystallinity. Results showed that hysteresis was increased by increasing hard phase crystallinity. This was the case for polyurethanes based on the novel diisocyanate 4,4’-dibenzyl diiscyanate (DBDI). The extent of stress rela...
Thermoplastic polyurethanes with isosorbide chain extender
Journal of Applied Polymer Science, 2015
Isosorbide, a renewable diol derived from starch, was used alone or in combination with butane diol (BD) as the chain extender in two series of thermoplastic polyurethanes (TPU) with 50 and 70% polytetramethylene ether glycol (PTMEG) soft segment concentration (SSC), respectively. In the synthesized TPUs, the hard segment composition was systematically varied in both series following BD/isosorbide molar ratios of 100:0; 75:25; 50:50; 25:75, and 0:100 to examine in detail the effect of chain extenders on properties of segmented polyurethane elastomers with different morphologies. We found that polyurethanes with 50% SSC were hard elastomers with Shore D hardness of around 50, which is consistent with assumed co-continuous morphology. Polymers with 70% SSC displayed lower Shore A hardness of 74-79 (Shore D around 25) as a result of globular hard domains dispersed in the soft matrix. Insertion of isosorbide increased rigidity, melting point and glass transition temperature of hard segments and tensile strength of elastomers with 50% SSC. These effects were weaker or non-existent in 70% SSC series due to the short hard segments and low content of isosorbide. We also found that the thermal stability was lowered by increasing isosorbide content in both series. V C 2015
Rheological characterization of thermoplastic polyurethane elastomers
Polymer International, 2000
The relationship between the rheological properties and composition of eight thermoplastic polyurethane elastomers (TPUEs) was evaluated using a stress-controlled rheometer. The composition of the TPUEs was changed by varying the OH/NCO ratio, the chain extender and the molecular weight of the macroglycol used in the synthesis. A high molecular weight macroglycol and a low OH/NCO ratio improved the rheological properties of the TPUEs due to the formation of longer or more abundant soft segments, respectively. The nature of the chain extender in¯uenced the rheological properties to a lesser extent.