Effects of mixing procedure on the structure and physical properties of ester–ether-type soft segment waterborne polyurethane

The effects of the mixing procedure for the preparation of ester-ether-type waterborne polyurethane (WBPU) on the structure and properties of the cast film are studied here. The following three types of WBPU processing are examined: film formed from WBPU mixing ether-type WBPU with ester-type WBPU (CEM series), film formed from WBPU synthesized with PEG2000 and PCL2000 polydiol as the soft segments (CEB series), film formed from WBPU synthesized with triblock ester-ether copolydiol (PCL-polyethylene glycol-PCL) as the soft segment (CET series). The water vapor permeability (WVP) for the application to nylon fabrics is also studied. The results show that the mixing procedure greatly affects the properties of the ester-ether-type WBPU. The CEB series has better phase mixing than the CET series, and the CEM series has a phase boundary between the ester-and ether-type WBPU. The CEM series has a better Young's modulus and breaking stress and poorer breaking strain than the CEB and CET series. In addition, samples with lower ethylene oxide (EO) content have better phase mixing and mechanical properties. On the other hand, the ester-ether-type WBPU has a higher WVP than the ester-type WBPU and the WVP increases with the EO content. The order of the mixing procedures for WVP is CET > CEB > CEM. © 1996 John Wiley & Sons, Inc.     

Effect of polyisocyanate hardener on adhesive force of waterborne polyurethane adhesives

A series of waterborne polyurethane (WBPU)/hardener adhesives were obtained from mixing of WBPU containing different types of polyol as a soft segment with aliphatic and aromatic polyisocyanates hardeners. By characterization of allophanate and biuret bonds formed from the reaction of hardener NCO with urethane/urea groups of WBPU using ¹HNMR spectroscopy. It was found that the optimum number ratio (molar ratio) of NCO group of hardener to urethane/urea group of WBPU that shows the highest adhesion force was depended on the type of hardener (aliphatic/aromatic polyisocyanate) and dimethylol propionic acid (DMPA) content (total content of urethane/urea groups); however independent of the type of soft segment (polyol) of WBPU. The optimum number ratio (molar ratio) of NCO group of aromatic polyisocyanate hardener to urethane/urea was higher than that of aliphatic hardener to achieve the highest adhesion force of WBPU. The adhesive force increased with increasing hardener content up to the optimum point and then decreased. Poly(tetramethylene adipate glycol) (PTAd) based WBPUs with aliphatic hardener show higher adhesive force than Poly(tetramethylene oxide glycol) (PTMG) and aliphatic hardener‐based WBPUs at the optimum number ratio (molar ratio) of NCO group of hardener to urethane/urea group of WBPU. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3663–3669, 2007     

PCL–PEG–PCL triblock ester–ether copolydiol-based waterborne polyurethane. II. Effect of NCO/OH mole ratio and DMPA content on the physical properties

This article was focused on the effects of the NCO/OH molar ratio and 2,2-bis(hydroxyl methyl) propionic acid (DMPA) content during prepolymerization on the physical properties of synthesized waterborne polyurethane (WBPU) by using the polycaprolactone–poly(ethyl glycol)–polycaprolactone triblock copolydiol (PCL–PEG–PCL) as the soft segment. The results showed that the particle size of the WBPUs' dispersion decreased with a decreasing NCO/OH molar ratio or increasing DMPA content. Regarding thermal and mechanical properties, the WBPUs had a higher T_g's and lower T_m's and a higher breaking stress and a lower breaking strain of film with the NCO/OH molar ratio or DMPA content increase. The increasing NCO/OH molar ratio was advantageous to the water vapor permeability (WVP)-breaking stress balance, but the effect of the DMPA content on the WVP was not significant. The WBPU with PCL–PEG–PCL as the soft segment had a smaller particle size in dispersion and a better WVP-breaking stress balance than those of WBPU with the blending PCL and PEG as the soft segment. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1301–1311, 1998     

Effect of Poly(dimethylsiloxane) Content on the Properties of Water-Borne Poly(urethane-urea)s Containing MDI

Low photo- and water-resistance is often cited as the problem of MDI-based WBPU. This study addressed this problem. Water-borne poly(urethane-urea)s (WBPUs) were synthesized using a pre-polymer mixing process from 4,4'-methylenebis(phenyl isocyanate)(MDI)/4,4-dicyclohexylmethyl diisocyanate (H₁₂MDI) (15/85 mole %)/dimethylol propionic acid (DMPA)/ethylene diamine (EDA)/triethylamine (TEA) with different poly(propylene glycol) (PPG, M _n = 2000)/hydroxyl terminated poly(dimethylsiloxane) (PDMS, M _n = ～550) molar ratios. This study highlights the effect of PDMS content on the inherent viscosity, hydrogen-bonding, storage modulus, tan δ peak intensity, tensile modulus/strength, elongation (%) at break, water swelling (%), contact angle, and the yellowness index of WBPUs containing MDI. The mechanical properties (strength/modulus), water-resistance and photo-resistance of WBPUs containing MDI increased significantly in proportion to the PDMS content. These results indicate the potential for using multi-performance WBPU with PDPS for WBPU coatings.     

Synthesis and properties of waterborne poly(urethane urea)s containing polydimethylsiloxane

To obtain flexible waterborne poly(urethane urea) (WBPU) coatings with functionalities such as shape recovery and water resistance, we synthesized a series of WBPUs by a prepolymer mixing process from hexamethylene diisocyanate, polyol, 2,2‐bis(hydroxymethyl) propionic acid, ethylenediamine, and triethylamine with polyol blends [hydroxyl‐terminated polydimethylsiloxane (PDMS) with a number‐average molecular weight of ≈ 550 and poly(tetramethylene oxide) glycol (PTMG) with a number‐average molecular weight of 650] of different molar ratios. The effects of the PDMS content in PDMS/PTMG on the dynamic thermal and mechanical properties, hardness, tensile properties, water resistance (water absorption, contact angle, and surface energy), and shape‐memory properties of WBPU films were investigated. As the molar percentage of PDMS in WBPUs increased, the storage modulus, tensile strength and modulus, elongation at break, hardness, and shape‐retention rate (30–15%) decreased; however, the water resistance and shape‐recovery rate (80–90%) increased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study on polyethylene glycol/polydimethylsiloxane mixing soft‐segment waterborne polyurethane from different mixing processes

The surface structure and physical properties of polyethylene glycol series polyurethane (PEG‐PU) membranes, in which were introduced hydrophobic polydimethylsiloxane (PDMS) component by the procedure of PU blending or of soft‐segment copolymerization, were studied in this investigation. In the case of the blending process, the synthesized waterborne polyurethanes (WBPUs) of PEG–PU and of polydimethylsiloxane series polyurethane (PDMS–PU) were combined, whereas in the copolymerization process PEG and PDMS were taken as mixed soft segments to polymerize the WBPU. For the blending method, glass‐transition and melting temperatures increased rapidly when a small amount of PDMS–PU was added to PEG–PU and reached a maximum with 5% PDMS–PU mixed in. However, in the case of the copolymer method, thermal properties closely followed predicted values. From dynamic mechanical analysis studies it was found that a low PDMS–PU content ratio could increase the rubbery elasticity of PEG–PU membrane and improve its strength simultaneously in the blending method, and the copolymer method only caused PU to gain some natural complementary strength and elasticity. Electron spectroscopy for chemical analysis studies indicated that PDMS migrated to the surface much more easily in the blending method than in the copolymer method. The SEM studies also found that, in the blending method, the numbers of pores were less than those in the copolymer method. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 233–243, 2003     

Preparation and characterization of waterborne polyurethane containing PET waste/PPG as soft segment

Soft drinks poly(ethylene terephthalate) (PET) bottles were depolymerized by glycolysis using a 1 : 3 molar ratio of PET repeating unit to glycols like neopentyl glycol (NPG) and dipropylene glycol (DPG). Further, a series of waterborne polyurethanes (WPUs) was synthesized using pure polypropylene glycol (PPG), and glycolyzed oligoesters/PPG blends in different molar ratios as soft segment. Thermal property of WPU was tested by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Moreover, viscosity and particle size of WPU were also investigated. The results show that introduction of a certain amount of glycolyzed oligoester to soft segment makes the degree of hard‐soft domain microphase separation smaller, and can also improve thermal stability of WPU. Furthermore, WPUs synthesised from glycolyzed oligoesters and PPG blends possess larger particle size, better particle size distribution, relative lower and more stable viscosity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42757.     

Structural characterization and mass transfer properties of polyurethane block copolymer: influence of mixed soft segment block and crystal melting temperature

An attempt has been made to investigate the influence of mixed soft segment on structure and mass transfer properties of segmented polyurethane (SPU). For this purpose polyurethane block copolymer containing soft segment such as polycaprolactone glycol (number‐average molecular weight 3000, PCL 3000), PCL 3000–polypropylene glycol (number‐average molecular weight 3000, PPG 3000), PCL 3000–polytetramethylene glycol (number‐average molecular weight 2900, PTMG 2900), PPG 3000–PTMG 2900, were synthesized using a two‐step or three‐step synthesis process. All the SPUs were modified with the hydrophilic segment, i.e. diol‐terminated poly(ethylene oxide) (number‐average molecular weight 3400, PEG 3400). Fourier‐transform infrared, wide‐angle X‐ray diffraction, differential scanning calorimetry, and dynamic mechanical thermal analysis were used to characterize the polyurethanes. The mass transfer properties were measured by equilibrium sorption and water vapor permeability measurements. Mixed blocks loosen the inter‐chain interaction due to phase mixing which decreases the crystallization of the soft segment in the resulting SPU. The crystallinity of mixed polyol block SPU increases when both polyols are crystallizable in the pure state. Highest loss tan δ value was observed for the sample containing PTMG 2900–PPG 3000 mixed soft segment due to their flexible and phase mixed structure which increases the chain mobility; this sample performed best among all four SPUs in equilibrium water sorption as well as water vapor permeability owing to their loose and nearly amorphous structure. Soft segment crystal melting further enhances the water vapor permeability significantly, which would make the membrane suitable for breathable textiles, packaging and medical applications. Copyright © 2006 Society of Chemical Industry     

Preparation and properties of MDI/H12MDI‐based water‐borne poly(urethane‐urea)s—Effects of MDI content and radiant exposure

Water‐borne poly(urethane‐urea)s (WBPUs) were prepared by a prepolymer mixing process using aromatic diisocyanate (MDI, 4,4′‐diphenylmethane diisocyanate)/aliphatic diisocyanate (H₁₂MDI, 4,4′‐methylenebis cyclohexyl isocyanate), polypropylene glycol (PPG, M_n = 1000), dimethylol propionic acid, and ethylene diamine as a chain extender, and triethylamine as a neutralizing agent. The effect of MDI on the molecular weight, chemical structure, dynamic thermo, and tensile properties of WBPUs was investigated. The yellowness index (YI, photo‐oxidation behavior) change of WBPUs under accelerated weathering exposure was also investigated. The WBPUs containing higher MDI content showed lower molecular weight, which verified the participation of some high reactive isocyanate groups of MDI into side reaction instead of chain growing reaction. As the MDI content increased, the storage modulus and tensile modulus/strength of WBPUs film increased, and their glass transitions of soft segments (T_gs) and hard segments (T_gh) were shifted to higher temperature. The intensity of tan δ peak of all three samples increased with increasing radiant exposure. The YI of H₁₂MDI‐based WBPU sample (WBPU‐0) was not occurred. The YI of WBPUs containing MDI increased with increasing MDI content and radiant exposure. However, the YI of sample WBPU‐25 containing 25 mol % of MDI at 11.3 MJ/m² (radiant exposure) was 6.6 which is a permissible level for exterior applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Properties of polyisobutylene polyurethane block copolymers: 2. Macroglycols produced by the ‘inifer’ technique

The structure-property relationships of a series of 4,4′-diphenylmethane diiscoyanate (MDI) based polyisobutylene (PIB) polyurethanes were investigated. The PIB glycol was synthesized via the ‘inifer’ technique and had a narrow functionality distribution with a number average functionality of 2.0. The use of a PIB glycol with improved functionality and solution polymerization of the polyurethane led to improved mechanical properties compared with previously studied PIB polyurethanes. However, the mechanical properties were still low compared with conventional polyurethanes; the absence of soft segment strain-induced crystallization and compositional heterogeneity due to reactant incompatibility are cited as possible causes of low mechanical properties. Sample compositions were designed for independent investigation of the effects of hard segment content and soft segment molecular weight on the properties of the materials. Increasing hard segment content resulted in improved dynamic and tensile modulus, lower elongation at break, and larger hard segment domains. Increasing soft segment molecular weight led to larger domains and reduced mechanical properties. The degree of phase separation as measured by the soft segment T_g and the amount of interfacial mixing measured by small angle X-ray scattering (SAXS) were unaffected by hard segment content and soft segment molecular weight and were indicative of a high degree of phase separation compared with conventional polyurethanes.     

Effect of the degree of soft and hard segment ordering on the morphology and mechanical behavior of semicrystalline segmented polyurethanes

The hierarchical microstructure responsible for the unique energy-absorbing properties of natural materials, like native spider silk and wood, motivated the development of segmented polyurethanes with soft segments containing multiple levels of order. As a first step in correlating the effects of crystallinity in the soft segment phase to the hard segment phase, we chose to examine the morphology and mechanical behavior of polyurethanes containing polyether soft blocks with varying tendencies to crystallize and phase segregate and the evolution of the microstructure with deformation. A series of high molecular weight polyurethanes containing poly(ethylene oxide) (PEO) (1000 and 4600 g/mol) and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) (1900 g/mol) soft segments with varying hard segment content were synthesized using a two-step solution polymerization method. The presence of soft segment crystallinity (PEO 1000 g/mol) was shown to improve the storage modulus of the segmented polyurethanes below the T_m of the soft block and to enhance toughness compared to the PEO-PPO-PEO soft segment polyurethanes. We postulate that this enhancement in mechanical behavior is the result of crystalline soft regions that serve as an additional load-bearing component during deformation. Morphological characterization also revealed that the microstructure of the segmented polyurethanes shifts from soft segment continuous to interconnected and/or hard domain continuous with increasing hard segment size, resulting in diminished ultimate elongation, but enhanced initial moduli and tensile strengths. Tuning the soft segment phase crystallinity may ultimately lead to tougher polyurethane fibers.     

Properties of polyisobutylene polyurethane block copolymers: 3. Hard segments based on 4,4′-dicyclohexylmethane diisocyanate (H12MDI) and butane diol

A series of polyisobutylene (PIB) polyurethanes based on 4,4′-dicyclohexylmethane diisocyanate (H₁₂MDI) have been synthesized and their structure-property relationships have been investigated. The PIB glycol was synthesized by the ‘inifer’ technique. Sample compositions were designed for independent investigation of the effects on physical properties of hard segment content and soft segment molecular weight and for comparison with corresponding 4,4′-diphenylmethane diisocyanate (MDI) based PIB polyurethanes. Increasing hard segment content resulted in improved dynamic and tensile modulus while elongation at break was unaffected. Increasing soft segment molecular weight led to decreased mechanical properties attributed to larger domain sizes as indicated by small angle X-ray scattering (SAXS). Both the soft segment T_g and the extent of interfacial mixing as measured by SAXS were unaffected by hard segment content and soft segment molecular weight suggesting that the materials were highly phase separated. In comparison with corresponding MDI based materials the H₁₂MDI based polyurethanes exhibited less hard segment ordering, slightly less interfacial mixing, smaller domain sizes, and slightly better ultimate tensile properties.     

Effect of soft segment molecular weight on tensile properties of poly(propylene oxide) based polyurethaneureas

Influence of soft segment molecular weight and hard segment content on the morphology, thermomechanical and tensile properties of homologous polyurethaneurea copolymers based on narrow molecular weight poly(propylene oxide)glycol (PPG) oligomers were investigated. A series of polyurethaneureas with hard segment contents of 12–45% by weight and PPG number average molecular weights <M_n> of 2000 to 11,800 g/mol were synthesized and characterized structurally by SAXS and mechanically by DMA and stress strain analysis. Bis(4-isocyanatocyclohexyl)methane and 2-methyl-1,5-diaminopentane were used as the diisocyanate and the chain extender respectively. All copolymers displayed microphase separation by SAXS and DMA. The critical entanglement molecular weight (M_e) of PPG is reported to be around 7700 g/mol. Our mechanical results suggest that when copolymers possess similar hard segment contents and are compared to those based on soft segments with number average molecular weights (M_n) greater than M_e, they generally displayed higher tensile strengths and particularly lower hysteresis and creep than those having soft segment molecular weights below M_e. These results imply that soft segment entanglements in thermoplastic polyurethaneureas may provide a critical contribution to the tensile properties of these copolymers – particularly in the range where the soft segment content is dominant.     

Influence of soft segment content and chain length on the physical properties of poly(ether ester) elastomers and fabrication of honeycomb pattern and electrospun fiber

Different series of poly(ether ester) (PEE) thermoplastic elastomers were synthesized using dimethyl-2,6-naphthalene dicarboxylate as hard segment, 1,4-butanediol as the chain extender, and three different soft segments of different molecular weights (MW), namely polycaprolactone diol (MW: 530 and 2000), poly(tetramethylene ether glycol) (MW: 1000 and 1800), and polycaprolactone-block-polytetrahydrofuran-block-polycaprolactone (MW: 2000). The composition of soft segment was changed from 30% to 50% with respect to the hard segment. The characteristic studies were focused to analyze the influence of the concentration and length of the soft segment content. In each series, 50:50 compositions of the hard and soft segments were found to show the best mechanical properties. In addition the physical properties of the elastomer were very sensitive to the type of soft segment. The elastomers prepared in this study were systematically characterized using various spectroscopic studies and thermal and mechanical analyses. As a means of discovering the feasibility of PEE elastomers as new functional materials honeycomb patterns and nanofibers have been fabricated by applying breath figures method and electrospinning, respectively, yielding uniform honeycomb structures and nanofibers of their diameter ranging from about 100 to 800 nm depending on the type of elastomer and the electrical potential employed .     

Synthesis and characterization of ambient-temperature self-crosslinked waterborne polyurethanes with a novel diol chain extender bearing two ketone groups

A series of ambient-temperature self-crosslinked waterborne polyurethanes denoted as WBPUs were successfully synthesized by incorporating a novel diol chain extender bearing two ketone groups, 2,2-bis(4-(2-hydroxypropoxy levulinate)phenyl)-propane (BHLPP), which was prepared using 2,2-bis(4-(2,3-epoxypropoxy)phenyl)-propane and levulinic acid, with 4,4-methylenedicyclohexyl diisocyanate, poly-neopentylene adipate glycol, and dimethylolpropionic acid. After post-adding adipic dihydrazide (ADH), self-crosslinking was achieved by the reaction between the ketone (–CO–) of BHLPP and the hydrazine (–NHNH₂) of ADH during film formation. For comparison, noncrosslinked waterborne polyurethane (WPU) without BHLPP and ADH was prepared. The structure of BHLPP was characterized by IR and NMR. The properties of the WPU and WBPU dispersions were investigated by measuring the stability, particle size, and morphology. The effects of the ratio of n(–NHNH₂)/n(–CO–) and the content of BHLPP were studied in terms of hardness, water resistance, solvent resistance, and thermal properties of WPU and WBPU films. The WBPU dispersions exhibited excellent stability, bimodal distribution, and regular spheroid morphology. The optimal ratio of n(–NHNH₂)/n(–CO–) for ketone–hydrazine self-crosslinking was 0.75:1. Importantly, the WBPU films showed superior hardness, water resistance, solvent resistance, and thermal properties to WPU film.     

Structure–property relationships of poly(urethane urea)s with ultra‐low monol content poly(propylene glycol) soft segments. I. Influence of soft segment molecular weight and hard segment content

Structure–property relationships in poly(urethane urea)s synthesized with ultra‐low monol content poly(propylene glycol) soft segments were investigated as soft segment molecular weight (2000, 4000, and 8000 g/mol) and hard segment content (6.3 and 9.0 wt %) were varied. Morphological features such as interdomain spacing and interphase thickness were quantified and revealed with small‐angle X‐ray scattering (SAXS) and atomic force microscopy (AFM). The thermal and mechanical behavior was assessed with a dynamic mechanical analyzer (DMA) and by differential scanning calorimetry (DSC) and stress‐strain tests. Hard segment content, over the limited range studied, had little effect on the morphology and soft segment thermal and mechanical properties. The molecular weight of the soft segments had considerably more influence on the morphology and mechanical properties. Increasing soft segment molecular weight resulted in greater interdomain spacings, as shown by SAXS, and a noticeable change in the structure, as shown by AFM. Additionally, as soft segment molecular weight decreased the soft segment glass transition broadened and rose to higher temperatures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 229–243, 2002; DOI 10.1002/app.10168     

软段对热塑性聚氨酯弹性体结构及性能的影响

以二苯基甲烷-4,4′-二异氰酸酯(MDI)和扩链剂1,4-丁二醇(BDO)为聚氨酯弹性体硬段(控制硬段质量分数32%),以实验室自制聚己二酸乙二醇酯二醇(PEA)和聚己二酸乙二醇丙二醇酯二醇(PEPA)为软段,经预聚体法合成不同结构的热塑性聚氨酯弹性体(TPU)。研究了弹性体软段部分对其硬度、力学性能和结晶性能的影响。结果表明,控制热塑性聚氨酯弹性体硬段部分不变,改变软段,材料硬度变化不大;软段聚酯二元醇随其相对分子质量的增加,TPU力学性能和结晶性能均增强;研究不同PG含量的软段PEPA-TPU发现,当PG质量分数为10%时,TPU力学性能与结晶性能最好。     

Thermoplastic polyurethane elastomers based on polycarbonate diols with different soft segment molecular weight and chemical structure: Mechanical and thermal properties

A series of thermoplastic polyurethane elastomers based on polycarbonate diol, 4,4′‐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. SCI., 2008. © 2007 Society of Plastics Engineers     

Structure–property relationships of polycarbonate diol‐based polyurethanes as a function of soft segment content and molar mass

Segmented thermoplastic polyurethanes (PUs) have been synthesized with polycarbonate diol as soft segment and 4,4′‐diphenylmethane diisocyanate and butanediol as hard segment. Two different series employing two different soft‐segment molar mass, 1000 and 2000 g/mol, and by changing the hard‐segment content from 32 to 67% have been investigated with the aim to elucidate the effect of the different content variations on the properties. Morphological, thermal, and mechanical properties have been studied by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), wide angle X‐ray diffraction, atomic force microscopy, tensile and tear strength, hardness, and specific gravity tests. Properties have been explained from the standpoint of miscibility between hard‐ and soft‐segment microdomains of the tailored segmented PUs through an exhaustive analysis. FTIR, DSC, and DMA measurements revealed that miscibility between hard and soft microdomains increases as the molar mass of the macrodiol decreases. An increase in hard‐segment content entailed the formation of larger hard domains with higher crystallinity what results in superior mechanical properties such as higher tensile stress and tear strength, and hardness. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41704.     

Structure-property behavior of segmented polyurethaneurea copolymers based on an ethylene-butylene soft segment

Novel segmented polyurethaneurea copolymers were synthesized using a poly(ethylene-butylene) glycol based soft segment and either hydrogenated diphenyl methane diisocyanate (HMDI) or hexamethylene diisocyanate (HDI) in addition to either ethylene diamine (EDA) or 2-methyl-1,5-diaminopentane (DY) as the chain extender. Dynamic mechanical analysis (DMA), small angle X-ray scattering (SAXS) and in some cases atomic force microscopy (AFM) established the presence of a microphase-separated structure in which hard microdomains are dispersed throughout a soft segment matrix. Wide angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) imply that the materials are amorphous. Samples that are made with HMDI/DY and have hard segment contents in the range of 16-23 wt% surprisingly exhibit near-linear mechanical deformation behavior in excess of 600% elongation. They also show very high levels of recoverability even though their hysteresis is also considerable. The materials have all proven to be melt processable in addition to solution processable.