Poly Oxytetramethylene Glycol Research Articles

Properties of Block Copolymers of Poly(Butylene Terephthalate) and Polyoxytetramethylene Glycol

Synthesis of polyester thermoelastoplasts, block copolymers of polyoxytetramethylene glycol and poly(butylene terephthalate) of the polyblock type, was developed and implemented in pilot industrial conditions. POTM blocks act as flexible molecular decouplings that give the copolymer elasticity, while PBT blocks form physical linkages and are responsible for the mechanical strength and hardness of the material. The composition of the reaction systems, process stage sequence, and synthesis parameters are optimized for block copolymers with a concentration of the flexible POTM block of 65-10 wt. % and a molecular weight of 1000. The structure is investigated, and the physicochemical and mechanical properties of the material obtained are determined. It was found that the concentration of flexible blocks has a determining effect on the physicochemical structure and properties of the block copolymers. For a ∼40% concentration of the flexible block, the character of the concentration curves of the physicomechanical indexes changes significantly due to phase-structural transformations in the block copolymers.

Structure development in aromatic polycyanurate networks modified with hydroxyl-terminated polyethers

A series of polycyanurate networks (PCN), based on the dicyanate of bisphenol A monomer (DCBA), was synthesized in the presence of different contents of hydroxyl-terminated polyethers (PEth), such as polyoxypropylene glycol (PPG) and polyoxytetramethylene glycol (PTMG). We studied the influence of the nature of the oligomeric modifier, initially miscible with DCBA, on the chemical structure, glass transition behaviour, phase morphology and mechanical properties of modified PCN. The possibility of PEth incorporation into the PCN structure through mixed cyanurate ring formation is discussed. A maximum PEth incorporated content of 0.1mol of PEth per mol of DCBA irrespective of PEth type has been detected. Dynamic mechanical thermal analysis (DMTA) analysis showed the formation of multiphase polymer compositions due to microphase separation of the components occurring during DCBA/PPG curing. The formation of very finely divided morphologies with highly interpenetrated phases, i.e. a PCN-rich phase, a mixed phase of PCN/PPG components and a PPG-rich phase was determined. On the other hand, all PCN/PTMG cured compositions exhibited a single, broad glass transition that shifted to lower temperature as the modifier content was increased and the experimental Tg versus modifier content showed a slight positive deviation from the Fox equation for miscible polymer systems. It can be concluded that the PCN and the PTMG have a higher degree of compatibility than PCN and PPG. The introduction of small additions of modifier (<10wt%) allow production of the thermosets with high Tg and good strength properties.

Thermal stability of polyurethane elastomers before and after UV irradiation

In this work, we investigated the thermal degradation behavior of segmented polyurethane (PUR) elastomers before and after UV irradiation. The thermal degradation of PUR elastomers was studied over the temperature range of 25–600°C in an atmosphere of nitrogen using thermal gravimetric analysis (TGA). Four series of PUR elastomers derived from poly(oxytetramethylene)glycol (PTMO) of 1000 and 2000 molecular weight and poly(caprolactone glycol) (PCL) of 1250 molecular weight, 4,4′-diphenylmethane diisocyanate (MDI), and 4,4′-dicyclohexylmethane diisocyanate (H12MDI) and 1,4-butanediol as an chain extender were synthesized by the prepolymer method. The derivative thermogravimetric (DTG) peaks observed in the experiments indicated that PUR elastomers degraded through two steps. We attributed the first step to degradation of the hard segment. The second degradation step could be ascribed to degradation of the soft segment. We found that the PUR elastomers based on poly(ester polyol) and aromatic diisocyanate exhibit better thermal stability than that of PUR elastomers based on the poly(ether polyol) soft segment in both steps of degradation. The thermal degradation is more prevalent in PUR elastomers based on cycloaliphatic diisocyanate. The higher values of the temperature of initial decomposition (Ti) indicate a higher thermal stability of UV-exposed elastomers on the beginning of degradation. This may be due to the formation of a crosslinking structure in the presence of UV irradiation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 864–873, 2001

Polyurethanes containing sulfur. I. New thermoplastic polyurethanes with benzophenone unit in their structure

New thermoplastic nonsegmented thiopolyurethanes were obtained from the low-melting aliphatic–aromatic thiodiols 4,4′-bis(2-hydroxyethylthiomethyl)benzophenone (BHEB), 4,4′-bis(3-hydroxypropylthiomethyl)benzophenone (BHPB), and 4,4′-bis(6-hydroxyhexylthiomethyl)benzenophenone(BHHB) as well as hexamethylene diisocyanate (HDI), both by melt and solution polymerization with dibutyltin dilaurate as the catalyst. The effect of various solvents on molecular-weight values was examined. The polymers with the highest reduced viscosities (0.63–0.88 dL/g) were obtained when the polymerization was carried out in a solution of tetrachloroethane, N,N-dimethylacetamide, and N,N-dimethylacetamide or N,N-dimethylformamide for BHEB-, BHPB-, and BHHB-derived polyurethanes, respectively. These polymers with a partially crystalline structure showed glass-transition temperatures (Tg) in the range of −1 to 39 °C, melting temperatures (Tm) in the range of 107 to 124 °C, and thermal stabilities up to 230 to 240 °C. The BHEB-derived polyurethane is a low-elasticity material with high tensile strength (ca. 50 MPa), whereas the BHPB- and BHHB-derived polyurethanes are more elastic, showing yield stress at approximately 16 MPa. We also obtained segmented polyurethanes by using BHHB, HDI, and 20 to 80 mol % poly(oxytetramethylene) glycol (PTMG) of M̄n = 1000 as the soft segment. These are high-molecular thermoplastic elastomers that show a partially crystalline structure. Thermal properties were investigated by thermogravimetric analysis and differential scanning calorimetry. The increase in PTMG content decreases the definite Tg and increases the solubility of the polymers. These segmented polyurethanes exhibit the definite Tg (−67 to −62 °C) nearly independent of the hard-segment content up to approximately 50 wt %, indicating the existence of mainly phase-separated soft and hard segments. Shore A/D hardness and tensile properties were also determined. As the PTMG content increases, the hardness, modulus of elasticity, and tensile strength decrease, whereas elongation at break increases. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4140–4150, 1999

Polyurethanes containing sulfur. I. New thermoplastic polyurethanes with benzophenone unit in their structure

New thermoplastic nonsegmented thiopolyurethanes were obtained from the low-melting aliphatic–aromatic thiodiols 4,4′-bis(2-hydroxyethylthiomethyl)benzophenone (BHEB), 4,4′-bis(3-hydroxypropylthiomethyl)benzophenone (BHPB), and 4,4′-bis(6-hydroxyhexylthiomethyl)benzenophenone(BHHB) as well as hexamethylene diisocyanate (HDI), both by melt and solution polymerization with dibutyltin dilaurate as the catalyst. The effect of various solvents on molecular-weight values was examined. The polymers with the highest reduced viscosities (0.63–0.88 dL/g) were obtained when the polymerization was carried out in a solution of tetrachloroethane, N,N-dimethylacetamide, and N,N-dimethylacetamide or N,N-dimethylformamide for BHEB-, BHPB-, and BHHB-derived polyurethanes, respectively. These polymers with a partially crystalline structure showed glass-transition temperatures (Tg) in the range of −1 to 39 °C, melting temperatures (Tm) in the range of 107 to 124 °C, and thermal stabilities up to 230 to 240 °C. The BHEB-derived polyurethane is a low-elasticity material with high tensile strength (ca. 50 MPa), whereas the BHPB- and BHHB-derived polyurethanes are more elastic, showing yield stress at approximately 16 MPa. We also obtained segmented polyurethanes by using BHHB, HDI, and 20 to 80 mol % poly(oxytetramethylene) glycol (PTMG) of M̄n = 1000 as the soft segment. These are high-molecular thermoplastic elastomers that show a partially crystalline structure. Thermal properties were investigated by thermogravimetric analysis and differential scanning calorimetry. The increase in PTMG content decreases the definite Tg and increases the solubility of the polymers. These segmented polyurethanes exhibit the definite Tg (−67 to −62 °C) nearly independent of the hard-segment content up to approximately 50 wt %, indicating the existence of mainly phase-separated soft and hard segments. Shore A/D hardness and tensile properties were also determined. As the PTMG content increases, the hardness, modulus of elasticity, and tensile strength decrease, whereas elongation at break increases. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4140–4150, 1999

Thermal and Phase Behavior of Polyurethane Based on Chain Extender, 2,2-Bis-[4-(2-hydroxyethoxy)phenyl]propane

A series of polyurethanes based on Poly(oxytetramethylene)glycol (PTMG), 4,4′-diphenylmethane diisocyanate (MDI) and 2,2-bis-[4-(2-hydroxyethoxy)phenyl]propane (BHPP) was synthesized by two-step solution polymerization varying PTMG soft segment length and hard segment content. Thermal and dynamic mechanical properties were studied by DSC and DMA. Solubility and interactions were calculated and quantitative assessment based on the shift of glass transition temperature and heat capacity change at glass transition was used to predict the extent of phase separation. DSC and DMA results showed that Tg shifted to higher temperature with increasing hard segment content and decreasing soft segment molecular weight, indicating partial phase mixing between hard and soft segment.

Deterioration of novel polyesterurethane elastomers in outdoor exposure

Poly(esterurethane)-elastomers based on novel polyester glycols with methyl side groups were exposed outdoors for 2 years. The polyester glycols used are poly(β-methyl-δ-valerolactone)glycol (PMVL), poly(3-methyl pentamethylene adipate) glycol (PMPA), poly(nonamethylene-co-2-methyl octamethylene carbonate) glycol (PNOC). A mixture of PNOC and poly(dimethyl siloxane)glycol (PNOC/PDMS) was also used. Polyurethane network elastomers, were prepared from these polymer glycols, 4,4′-diphenylmethane diisocyanate, and a mixture of 1,4-butanediol with trimethylol propane by a prepolymer method. The deterioration behavior of the PUEs was measured by means of polarizing microscopy, DSC, tensile testing, dynamic viscometry, and ESR. The novel polyester-based PUEs have better weatherability than poly(oxytetramethylene) glycol (PTMG)-based PUE. The mechanisms of deterioration are discussed. ©

Comparison of properties of thermoplastic polyurethane elastomers with two different soft segments

Two series of thermoplastic polyurethane elastomers [poly(propylene glycol) (PPG) based PP samples and poly(oxytetramethylene)glycol (PTMG) based PT samples] were synthesized from isophorone diisocyanate (IPDI)/1,4-butanediol (BD)/PPG and IPDI/BD/PTMG. The IPDI/BD based hard segments contents of polyurethane prepared in this study were 40–73 wt %. These polyurethane elastomers had a constant soft segment molecular weight (average Mn, 2000) but a variable hard segment block length (n, 3.5–17.5; average Mn, 1318–5544). Studies were made on the effects of the hard segment content on the dynamic mechanical thermal properties and elastic behaviors of polyurethane elastomers. These properties of PPG based PP and PTMG based PT samples were compared. As the hard segment contents of PP and PT samples increased, dynamic tensile modulus and α-type glass transition temperature (Tg) increased; however, the β-type Tg decreased. The permanent set (%) increased with increasing hard segment content and successive maximum elongation. The permanent set of the PT sample was lower than that of the PP sample at the same hard segment content. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1349–1355, 1998

Synthesis and Properties of Polyurethane Elastomer Graded Spherulite Size

Poly(oxytetramethylene)glycol (PTMG)-4,4′-diphenylmethane diisocyanate (MDI)-based polyurethane elastomer (PUE) was prepared by a mold with a temperature gradient. Effect of the temperature gradient on morphologies and mechanical properties were studied by DSC, polarizing microscopy, tensile test, micro-hardness test, friction test, and DIN abrasion test. The prepared PUE had graded super-structures. Spherulite sizes of the PUE depended significantly on the temperature gradient. Spherulite of PUE in contact with the mold at low temperature was significantly smaller and more dense than that contacting the mold at high temperature. Micro-hardness of the PUE linearly increased from low temperature mold side to the high temperature mold side. Friction coefficient of the surface contact with the low temperature mold plate became more lowered compared to the surface in contact with the high temperature mold plate. Abrasion resistance of the surface in contact with the low temperature mold plate evaluated by DIN abrasion test were better than that at the high temperature mold plate.

Phosphazene-modified polyurethanes: Synthesis, mechanical and thermal characteristics

Cyclotriphosphazene-containing trihydroxy and tetrahydroxy compounds were synthesized, characterized and examined as crosslinking agents (CLA) in polyurethane systems constituted independently with polyether polyols such as polyethylene glycol (PEG), polyoxytetramethylene glycol (POTMG) and polybutadiene polyol (HTPB) and reacted with tolylene diisocyanate. The effect of the nature and concentration of the crosslinking agent on the mechanical and thermal characteristics of the polyurethane network were studied and the results were compared with a system having trimethylol propane (TMP) as crosslinking agent. The tensile strength and glass transition temperature ( T g ) increased and elongation decreased with increasing concentration of the CLA. A relative improvement in these properties was higher for the phosphazene-containing systems vis-a-vis those containing an equivalent amount of conventional CLA such as TMP. Incorporation of phosphazene slightly increased the temperature of onset of decomposition of the PU and decreased the rate of degradation at elevated temperatures.

The effect of different molecular weight of soft segments in polyurethanes on photooxidative stability

The effect of molecular weight of polyol (soft segment) and the concentration of urethane (hard segment) in segmented polyurethane elastomers on their photodegradation was investigated. Polyurethane elastomers have been prepared from 4.4′-dipheylmethane diisocyanate (MDI) and poly(oxytetramethylene) glycol (PTMO) of 1000 and 2000 molecular weight at NCO OH ratios of 2 1 and 4 1 . Purified 1,4-butanediol (BD) was used as the chain extender. Mechanical, thermal, dynamic mechanical and Fourier Transform Infrared Spectroscopy (FTIR) measurements have been used for mechanical and structural studies of PUR elastomers before and after UV irradiation, for a better understanding of the role of the concentration of hard segments (urethane) and molecular weight of soft segments (polyol) in PUR. It was found that the molecular weight of soft segments as well as the NCO OH ratios have an influence on the UV stability of the examined elastomers. The photooxidative degradation is more prevalent in elastomers with lower hard segment concentration and with higher soft segment molecular weight. The correlation between the compositions of the investigated elastomers and mechanical properties, dynamic mechanical properties, physical transitions, as well as intensities of the changes of these properties after irradiation were established. The results show that with an increase of hard segment concentration in all examined polyurethane elastomers, the glass transition temperature ( T g ) of the soft segment increased, the tensile strength increased and the elongation at break decreased. In irradiated polyurethane elastomers based on PTMO (1000) with the higher hard segment concentration T g of the soft segment decreased, the opposite effect was obtained in PUR elastomer with lower hard segment concentration. Resistance to photooxidative degradation was enhanced with increase of the hard segment concentration in polyurethane elastomers based on PTMO (1000). The photooxidative degradation is more prevalent in polyurethane elastomers based on polyether with higher molecular weight PTMO (2000), than those based on polyether of molecular weight PTMO (1000), even at higher hard segment concentration.

Studies on thermotropic liquid crystalline polyurethanes. III. Synthesis and properties of polyurethane elastomers by using various mesogenic units as chain extender

Four series of thermotropic polyurethane elastomers (TPUEs) were synthesized in this study. The hard segments were formed by using 4,4′-methylenedicyclohexyl diisocyanate (H12MDI) reacted with various mesogenic units, such as benzene-1,4-di(4-iminophenoxy-n-hexanol), benzene-1,4-di(4-iminophenol), and 3,3′-(4,4′-biphenylene)dipropanol, which also acted as the chain extender. Poly(oxytetramethylene)glycols (PTMEGs), PTMEG-2000 (Mn 2,000) and PTMEG-1000 (Mn 1,000) were used as a soft segment. The structures of all synthesized thermotropic liquid crystalline polyurethanes (TLCPUs) were characterized by FTIR spectroscopy. The effects of mesogenic units on the LC properties and elastic behaviors of LCPUs were studied. It was difficult to show LC behaviors for the PU elastomers derived from the mesogenic units with a lower aspect ratio, such as 3,3′-(4,4′-biphenylene)dipropanol, or the long soft segments, PTMEG-2000. In addition, these PU elastomers show better elastic properties by using a higher aspect ratio mesogenic unit as the chain extender, such as benzene-1,4-di(4-iminophenoxy-n-hexanol and benzene-1,4-di(4-imino-phenol)). The thermal properties were investigated by DSC measurements, thermal optical polarized microscopy, wide angle X-ray diffraction, dynamic mechanical analysis, and thermogravimetric analysis. The mechanical properties were measured by a tensilemeter. © 1996 John Wiley & Sons, Inc.

Bromine — containing polyurethane ionomers

Polyurethane ionomers with reduced flammability were obtained by incorporating a brominated chain extender (dibromoneophentyl glycol-DBNPG) into the ionomers based on isophoronediisocyanate, polyoxytetramethylene glycol and 2,2-bis(hydroxymethyl)propionic acid. To examine the influence of brominated diol on the characteristics of the synthesized polymers, model polyurethane compounds containing various amounts of brominated and nonbrominated chain extenders (1,4-butanediol and neopenthyl glycol) were prepared, as well. The products were studied by FTIR, DSC and TGA methods. Hydrolytic stability of the ionomers in water was controlled by FTIR; their flammability was examined by oxygen index measurements.

ポリウレタンカチオノマーの多相構造と物性に及ぼすポリオール構造とＮ｀＋´濃度の効果

This paper reports the relation between the structure and the properties of polyurethane (PU) cationomers having various blend ratio of polyols and N+ concentration. NCO-terminated prepolymers were prepared from 2, 4-tolylene diisocyanate and polyols including poly (oxytetramethylene) glycol (PTMG), poly (oxypropylene) glycol (PPG) and two blended polyols which are PTMG/Poly (oxyethylene)glycol (PEG) (70/30mol%, abbreviated as 7T3E) and PPG/PEG (70/30 mol%, 7P3E). PU cationomers were obtained by chain-extension with the mixture of 1, 1, 1-trimethylolpropane, 1, 4-butanediol, and dimethyldiethanolammonium iodide. Thermal, dynamic mechanical, and tensile properties, and electric conductivity (complex impedance) of the resulting PU cationomers were studied. The compatibility between polyols and ions was found to decrease in the order of PEG>PPG>PTMG. The difference in compatibility caused variations in phase structure among PU cationomers. DSC and dynamic mechanical results suggested almost homogeneous (single phase) structure for 7P3E and microphase separation between PTMG and ionic phase for 10T (i.e. PTMG only). Tensile strength at break increased with N+ concentration due to the strong interaction among ions. PU cationomers containing PEG such as 7P3E and 7T3E, showed high electric conductivity.

Synthesis and Characterisation of Liquid-Crystalline Polyurethane Elastomers*

Polyurethane elastomers (PUEs) containing conventional and mesogenic hard segments were prepared from poly (oxytetramethylene)glycol (PTMG), 2.4-toluene diisocyanate, and mesogenic diols and/or 1,4-butanediol. The mesogenic diols used are 4,4'-bis(2-hydroxyethoxy)benzophenone, and dihydroxy-p-quarterphenyl. Effects of addition of mesogenic diol to 1.4-butanediol on mechanical, thermal properties, and morphologies of PUEs were investigated.

Studies on thermotropic liquid crystalline polyurethanes. II. Synthesis and properties of liquid crystalline polyurethane elastomers

AbstractThree series of novel thermotropic liquid crystalline polyurethane elastomers (TLCPUEs) were studied. Hard segments were formed by using hexamethylene diisocyanate (HDI) reacted with a mesogenic unit, benzene‐1,4‐di(4‐iminophenoxy‐n‐hexanol), which also acted as a chain extender. Three diols: 1,10‐decanediol,poly(oxytetramethylene) glycol (PTMEG) Mn = 1000 and PTMEG Mn = 2000 were used as the soft segments. The effects of soft segments of polyurethanes on the liquid crystalline behavior were studied. Higher molecular weight TLCPUEs were obtained by adding 30−50 mol % of mesogenic segments to diisocyanates. In contrast to a conventional chain extender such as 1,2‐ethylene glycol or 1,4‐butyl glycol, the synthesized polyurethane elastomers exhibited a mesophase transition by using a mesogenic unit as the chain extender. Mesophase was found for all synthesized LC polyurethanes except of polymers H2‐A‐12 and H2‐A‐7. The structures and the thermal properties of all synthesized TLCPUEs were studied by using FTIR spectroscopy, wide‐angle x‐ray diffraction (WAXD) and DSC measurements, a polarizing microscope equipped with a heating stage, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). Mechanical properties were also examined by using a tensilemeter. © 1995 John Wiley &amp; Sons, Inc.

Properties of Water-Absorbed Polyurethane Ionenes

Crosslinked polyurethane (PU) ionenes were prepared. NCO-terminated prepoly mer obtained from polyol blends of poly(oxytetramethylene)glycol (PTMG) and poly(oxyeth ylene)glycol (PEG) and 4,4'-methylenebis(phenylisocyanate) were made to react with 2- dimethylaminoethanol, resulting in amine-terminated (AT) prepolymer having isocyanurate ring in structure. By the reaction of AT-prepolymer with N,N,N' ,N'-tetramethyl-1,6-diaminohexane and 1,6-dibromohexane, crosslinked PU ionenes were obtained. Bound water existing in the hydrogel of crosslinked PU ionenes was determined by two methods. The amount of nonfreezing (bound) water determined by DSC was constant, ca. 9 water mol/[N+] mol, and not dependent upon the composition of PU ionenes. This type of water is considered to be the water strongly bound to [N+] ion site. On the other hand, the amount of bound water determined by drying measurement was greater than that determined by DSC measurement. In the drying mea surement, PU ionene containing larger amounts of PEG had larger amounts of bound water. The bound water determined by drying is considered to include water hydrated to polar ether [O] group in addition to nonfreezing water. 95 % of water existing in swollen hydrogel was free water, as in highly water-absorbing resin. Tensile properties of swollen gels were examined. It was suggested that the ionic aggregation that existed in dry state was destroyed in swollen state.

Effect of Soft Segment Molecular Weight and 3-Methyl Side Group on Microstructural Separation in Polyurethane Elastomers

Abstract The object of this study was to assess the effect of the chain length and of the pendant 3-methyl side group in the soft segment of polyurethane (PU) elastomers. In addition, the effect of annealing-quenching on the degree of microstructural segregation between the hard and soft segments was also investigated. The study employed electron spin resonance (ESR), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Samples for ESR measurements were spin-labeled with the nitroxide probe, 4-hydroxy-2,2′,6,6′-piperidine-1-oxyl (TEMPOL), by reaction of an isocyanate group with the hydroxyl group of TEMPOL. The nitroxide label is therefore located at a chain end. The PU's were based on 4,4′-diphenylmethane diisocyanate (MDI), poly(oxytetramethylene) glycols (PTMO), and hydroxyl-terminated random copolymers of tetrahydrofuran and 3-methyl-tetrahydrofuran (THF/Me-THF). Purified 1,4-butanediol (BD) was used as a chain extender. The elastomers made from higher molecular weight (MW) ...

Study of phase separation in polyurethane using paramagnetic labels. Effect of soft segment molecular weight, structure, and thermal history

AbstractThe morphology of segmented polyurethane (PU) elastomers was studied by means of ESR at various temperatures ranging from 100K‐450K. The PU's were based on 4,4'‐diphenylmethane diisocyanate (MDI), poly (oxytetramethylene) glycols (PTMO) and hydroxyl‐terminated random compolymers of tetrahydrofuran and 3‐methyl‐tetrahydrofuran (THF/Me‐THF). Purified 1,4‐butanediol (BD) was used as a chain extender. The nitroxide probe, 4‐hydroxy‐2‐2',6‐6'‐tetramethylpiperidine‐1‐oxyl (TEMPOL), was used to label the polyurethanes by reaction with an NCO group of MDI. Analysis of the electron spin resonance (ESR) spectra suggested that the label situates at heterogeneous sites, which means that a two‐phase domain is present. The morphologies at 300K and 400K were compared. It was found from ESR spectra that polyurethanes made from soft segments having higher MW exhibited greater phase separation at 300K than their corresponding elastomers made from lower MW soft segments. However, at 400K the more isotropic ESR spectra for the PUs containing higher MW soft segments suggested that the PUs were more mobile than their analogs having lower MW soft segments. The introduction of 3‐methyl side groups decreased the phase mixing at 400K due to steric hindrance.

Relation between the spectral characteristics of IR absorption bands in the urethane group and the rigid block content of linear polyetherurethanes

The structure of Amide I, IV and ν(NH) bands as a function of the rigid block content is studied using samples of polyetherurethanes based on polyoxytetramethylene glycol, 4,4′-diphenylmethane diisocyanate, and butanediol as examples. A decrease in the half-width of the ν(NH) band and a sharp increase in intensity of the component of the Amide I band at 1702 cm −1 and of the Amide V band at 660 cm −1, corresponding to the appearance, at 20% of highly ordered structures of rigid segments, which impart to polyetherurethane properties of cross-linked polymer, are observed.