A comparative study of the structure-property behavior of highly branched segmented poly(urethane urea) copolymers and their linear analogs

The solid-state structure-property behavior of highly branched segmented poly(urethane urea) (PUU) copolymers and their linear analog was investigated. A limited study of their solution rheological behavior was also undertaken. The linear PUUs were synthesized by the two-step prepolymer method, whereas the oligomeric A₂+B₃ methodology was utilized to synthesize the highly branched materials. The soft segments (SS) were either poly(tetramethylene oxide) (PTMO) or poly(propylene oxide) (PPO). All copolymers utilized in this study, with one exception, contained 28 wt% hard segment (HS) content. DMA, SAXS, and AFM studies indicated that the linear as well as the highly branched PUUs were microphase separated. The SS T_g of the highly branched PUUs was nearly identical to that of their respective linear analogs. However, the linear copolymers exhibited broader and less temperature sensitive rubbery plateaus, both attributed to one or both of two reasons. The first is better hydrogen bonding organization of the HS phase as well as greater HS lengths than in the highly branched analogs. The second parameter is that of a potentially higher chain entanglement for the linear systems relative to the branched analogs. Tapping-mode AFM phase images confirmed the microphase morphology indicated by SAXS and DMA. Ambient temperature strain-induced crystallization was observed in the PUU based on PTMO 2040 g/mol at a uniaxial strain of ca. 400%, irrespective of the chain architecture. Stress-strain, stress relaxation, and mechanical hysteresis of the highly branched copolymers were in general slightly poorer than that of their linear analogs. Ambient temperature solution viscosity of the highly branched materials in dimethyl formamide was substantially lower that that of the linear samples of nearly equal molecular weight.     

Polyurethaneurea aqueous dispersions prepared with diethyltoluenediamine as chain extender

A series of polyurethaneurea (PUU) aqueous dispersions either with diethyltoluenediamine (DETDA) or ethylenediamine (EDA) as chain extender were prepared with polyester polyol, isophorone diisocyanate and dimethylol propionic acid (DMPA), and characterized. It was found that the physical properties of the PUU aqueous dispersions prepared with DETDA were similar to or better than those prepared with EDA. Compared with the EDA-extended waterborne PUU films, the water resistance and the mechanical properties of the DETDA-extended waterborne PUU films were enhanced appreciably; these enhancements are attributed to the strong hydrogen bonding in urea carbonyl groups and the ordered structure of hard segments in the systems. The DETDA-extended PUU film with 40 wt.% of hard segment and 4.0 wt.% of DMPA unit showed the lowest water-absorbing amount (2.6 wt.%) over all PUU films studied. The hydrophobic surface of the DETDA-extended PUU film modified with a small amount of aminoethylaminopropyl polydimethylsiloxane (AEAPS) was observed and its hydrophobicity was enhanced by increasing the AEAPS content further.     

Mechanically strong waterborne poly(urethane-urea) films and nanocomposite films

A series of transparent waterborne poly(urethane-urea) (PUU) films and nanocomposite films were prepared using isocyanate excess (5–50 mol% excess relative to the hydroxyl groups) and omitting the common chain-extension step in the acetone method of the preparation. The surplus isocyanate groups were converted into urea and eventually biuret linkages via the reaction with water during the last phase inversion step. Nanocomposites were prepared by the direct mixing of the PUU nanoparticles in water with aqueous nanosilica or montmorillonite powder followed by slow water evaporation. Variable urea/biuret content is responsible for substantially different tensile properties; the neat organic films show elongation-at-break values of 100%–1120%, tensile strength values of 0.07–22.1 MPa, and energy-to-break of 0.1–85 mJ × mm⁻³. All of the materials can be potentially used as soft-to-hard topcoats, depending on the specific demands. The most promising materials are films prepared at 30 and particularly 40 mol% isocyanate excess.     

Preparation and characterization of waterborne polyurethaneurea composed of C9-diol-based polyester polyol

A series of polyurethaneurea (PUU) aqueous dispersions were prepared with C9-diol-based polyester polyol (POA) and/or poly(neopentylene adipate) polyol (PNA). The particle size and viscosity of the PUU aqueous dispersions consisting of POA were close to those of a comparable system prepared with PNA, and the high-temperature stability and freeze–thaw stability for all the aqueous dispersions were excellent. The PUU film prepared only with the POA exhibited the lowest water-absorbing amount, the highest tensile strength (51.3 MPa), and the best hydrolytic stability across all PUU films studied. The experimental results also showed a high degree of hydrogen bonding for urea groups and a perfect, ordered structure of hard segments in this kind of PUU film, resulting in excellent water-resistance performance and mechanical properties.     

Fluorinated waterborne shape memory polyurethane urea for potential medical implant application

A series of crosslinked fluorinated waterborne shape memory polyurethane urea (PUU) ionomers were synthesized from polycaprolactone diol, perfluoropolyether (PFPE) diol, dimethylolproionic acid, isophorone diisocyanate, ethylenediamine (EDA), and diethylenetriamine (DETA). The effect of PFPE content in the soft segment and the degree of crosslinking on the molecular structure and the properties of these PUU films was examined and studied. Differential scanning calorimetry showed that the transition temperature for these T_m type shape memory PUU could be fine tuned by PFPE weight percentage and EDA/DETA ratio in the range between 33 and 44°C, covering the range of body temperature. Although incorporating amorphous fluorinated units into semicrystalline soft segment compromised the shape memory performance of PUU with linear structure as expected, the introduction of crosslinking structure using DETA as a trifunctional chain extender could still retain quite high strain recovery rate (above 90%) at 100% stretching deformation. Furthermore, the relationship of these properties as well as thermal stability with hydrogen bonding was also discussed by evaluation of the carbonyl stretching region in Fourier transform infrared spectra. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

乙烯脲改性水性聚氨酯脲的制备与性能

采用一种新型的扩链剂乙烯脲(EU),在聚氨酯硬段引入具有刚性环状二取代脲基团,通过控制脲含量、交联度以及软段相对分子质量来制备一系列的EU改性水性聚氨酯脲(PUU-EU),并利用透射电镜(TEM)、广角X射线衍射(WAXD)、动态力学机械分析(DMA)、热失重分析(TGA)等测试方法,系统地研究PUU-EU微观结构与氢键化程度、微相分离、耐热性、力学强度的关系,并与1,4-丁二醇(BDO)扩链制备的水性聚氨酯(WPU)进行对比。结果表明,在一定范围内,PUU-EU随脲含量增加,其氢键化程度愈发完善,微相分离程度随之增加,力学强度逐步提高。     

Effects of soft-segment prepolymer functionality on the thermal and mechanical properties of RIM copolymers

Segmented copolyureas (PUr) and copoly(urethane–urea)s (PUU) comprising 50% by weight of polyurea hard segments (HS) and polyether soft segment (SS) with different functionalities, have been formed by reaction injection moulding (RIM). The HS were formed from 4,4′-diphenylmethane diisocyanate reacted with mixed isomers of 3,5-diethyltoluene diamine. The nominal functionality of the SS prepolymers used (either amino- or hydroxyl-functionalised polyoxypropylenes with a constant molar mass per functional group of ∼ 2000 g mol⁻¹) was systematically increased from 2 to 4. RIM materials were characterised using dynamic mechanical thermal analysis, differential scanning calorimetry, tensile stress–strain and fracture mechanics studies. Generally, the PUr exhibited far superior thermal-mechanical properties than equivalent PUU materials but inferior fracture resistance, owing to morphological variations resulting from differences in copolymerisation behaviour. For both systems, tensile behaviour was shown to be dominated by the degree of phase separation, whereas fracture properties showed a degree of dependence on SS functionality.     

Hydrophilic porous polymers based on high internal phase emulsions solely stabilized by poly(urethane urea) nanoparticles

Stable oil-in-water (o/w) Pickering high internal phase emulsions (HIPEs) having an internal phase of up to 95 vol% were prepared with a low-energy emulsification method. A poly(urethane urea) (PUU) aqueous nanodispersion was used as aqueous phase. The PUU nanoparticles of the aqueous nanodispersion acted as a mechanical barrier, and prevented droplet coalescence in the Pickering HIPEs. In addition, open porous hydrophilic polymer foams were obtained by polymerization of the Pickering HIPEs, and the morphology of the foams were tailored by changing the oil:water ratio, PUU nanoparticle and NaCl concentrations. The method used herein provides a simple way to prepare morphology controlled hydrophilic polymer foams using o/w Pickering HIPEs as template.     

Effect of polymer architecture and hard/soft segment ratio on the surface morphology and mechanical properties of polyurethane films for potential orthodontic treatment

In this study, polyurethane (PU) films are prepared by using 1,4-butanediol and trimethylolpropane as chain extender and crosslinking agent, respectively. A series of prepolymers are synthesized by varying the feeding molar ratios of methylene diisocyanate to polytetramethylene ether glycol, which are hard and soft segments, respectively. The influence of polymer architecture, chemical composition, and artificial saliva treatment on the surface morphology and mechanical strength of PU films are studied. The crosslinking polymer architecture and higher content of hard segment correlates with enhanced tensile strength and less decrease of tensile strength in the condition of artificial saliva, but reduced elongation at break. The in vitro cytotoxicity study demonstrates that PU films have excellent cytocompatibility.     

Tensile deformation and morphology changes in segmented elastomer films and fibers including mechanical property modeling

Segmented polyether soft segment (SS) elastomers with different hard segments (HS) in film and fiber form were studied by birefringence, DSC, and tensile tests. To understand the morphological contributions to property differences, high resolution tapping AFM resolved ribbon-like highly anisotropic hard domain (HD) lamellae in low modulus Pebax (polyamide 12 HS) and polyetherester (PEE), films, while lower HS content high melting poly(urethane urea) (PUU) had much smaller less anisotropic but higher melting HDs, explaining its enhanced thermal and mechanical hysteresis properties. Stress–strain tensile data demonstrate the excellent strength and toughness of PUUs and some spun PEE fibers, and film and fiber birefringence data applied during strain cycling up to very high stresses provided the molecular basis for the varying properties. The parameters from non-Gaussian fits of tensile data provide insight into network properties for these systems exhibiting very high strengths and a large degree of strain hardening. Modeling of PEE and Pebax films also shows the effects of substantial plastic yielding of the HD networks. Tensile data were obtained as a function of strain rate and temperature to help understand the contributions of network restructuring and other factors. For fibers, strain rate data spanning seven decades show and unusual drop in strengths at very high strain rates. Temperature-dependent tensile data also show large differences between PUU materials versus lower melting PEEs.     

The effects of latex coalescence and interfacial crosslinking on the mechanical properties of latex films

The effects of latex coalescence and interfacial crosslinking on the mechanical properties of latex films were extensively investigated by means of several series of model latexes with varying backbone polymer crosslinking density and interfacial crosslinking functional groups. It was found that the tensile strength of crosslinked model latex films increased with increasing gel content (i.e. crosslinking density) of latex backbone polymers up to about 75% and then decreased with further increase in gel, while their elongation at break steadily decreased with increasing gel content. These findings showed that latex particle coalescence was retarded above a gel content of about 75% so that the limited coalescence of latex particles containing gel contents higher than 75% prevented the tensile strength of crosslinked latex films from increasing by further crosslinking the latex backbone polymers. This was contrary to the theory of rubber elasticity that the tensile strength increases with increasing molecular weight and crosslinking density. This limitation was found to be overcome by the interfacial crosslinking among latex particles during film formation and curing. This paper will discuss the effects of both latex backbone polymer and interfacial crosslinking on latex film properties. It will also discuss the development of self-curable latex blends and structured latexes containing co-reactive groups: oxazoline and carboxylic groups.     

Phase-mixing and molecular dynamics in poly(urethane urea) elastomers by solid-state NMR

The dynamical heterogeneity in a series of 4,4′-dicyclohexylmethane diisocyanate-diethyltoluenediamine-poly(tetramethylene oxide) based poly(urethane urea) (PUU) elastomers was studied by solid-state nuclear magnetic resonance (NMR) methods. Extensive phase mixing was evidenced by the ¹H wideline signal, which can be approximately fitted by a single exponential model. ¹³C T₁ relaxation time measurements indicate that the hard segments (HS) exhibit some small-amplitude mobility, likely “activated” by neighboring soft segments (SS). Fitting of the time-domain wideline separation (TD-WISE) data was employed to characterize the extent of phase mixing, which revealed that a PUU elastomer contains four fractions: rigid-HS, mobile-HS, rigid-SS, and mobile-SS regions. For a variety of SS MWs, the dynamics and relative portions of rigid vs. mobile fractions among HS were substantially similar, while those for the SS exhibit large contrast. Furthermore, the dynamics in the rigid-SS fraction is at least an order of magnitude slower than that in mobile-SS for all PUUs. Greater phase-mixing substantially lowers the SS mobility, facilitating SS to undergo glass transition at high strain rates, thus can be key to enhancing dynamic mechanical strengthening.     

复合薄膜用水性聚氨酯胶粘剂的研究

以聚已二酸1,4-丁二醇酯(PBA)、甲苯二异氰酸酯(TDI)、二羟甲基丙酸(DMPA)等为主要原料合成了水性聚氨酯复膜胶,讨论了亲水性扩链剂DMPA用量对水性聚氨酯复膜胶的稳定性、耐水性、粘接强度等的影响;使用差示扫描量热仪(DSC)和原子力显微镜(AFM)观察了分子结构中的软、硬段微相结构分布。结果表明,当DMPA质量分数占预聚体总质量的2.67%～5.34%时能够制得稳定乳液;水性复膜胶乳液的粘度以及胶膜的吸水率随着亲水性扩链剂DMPA用量的增加而增加,而乳液的粒径随着亲水性扩链剂DMPA用量的增加而减小;硬段含量的增加会降低软段结晶,增加水性聚氨酯复膜胶高分子链的极性和粘接强度,当硬段质量分数为22.79%时,胶膜具有较好的T型剥离强度;提高复合压力能够显著提高T型剥离强度;该复膜胶对聚对苯二甲酸乙二醇酯(PET)膜有着比聚丙烯(OPP)膜更好的粘接效果。     

Poly(ether urethane)/poly(ethyl methacrylate) IPNs with high damping characteristics: The influence of the crosslink density in both networks

Interpenetrating polymer networks (IPNs) with a controlled degree of microphase separation were synthesized from a poly(ether urethane) (PUR) and poly(ethyl methacrylate) (PEMA). The influence of the crosslink density of both networks was investigated in the 70:30 PUR/PEMA IPN. The extent of damping was evaluated by dynamic mechanical thermal analysis. Mechanical properties were studied using tensile testing and hardness measure-ments. Control of crosslinking was successful in tailoring the damping profile. Higher crosslinking in the first-formed network (polyurethane) seemed to increase slightly the area under the linear loss modulus curve, LA, whereas no influence was obvious when changing the crosslink density in the second network. TGA studies revealed improved thermal properties for the IPNs with a higher crosslink density in the PUR network. TEM micrographs confirmed a finer morphology for the materials with a higher crosslink density in the PUR, whereas increasing the crosslink density in the PEMA network resulted in a decrease of phase mixing. © 1996 John Wiley & Sons, Inc.     

Thermal,mechanical, and fracture properties of copolyureas formed by reaction injection molding: Effects of hard segment structure

A series of copolyureas containing 50% by weight hard segment have been formed by RIM. The hard segment structure was systematically varied to investigate the effects of urea group density, hard segment crosslinking, relative reaction rates, and to compare the properties of aromatic and aliphatic hard segment materials. In each case the soft segment was based on a 2000 molecular weight polyether diamine. The RIM materials formed ranged from flexible elastomers to brittle plastics depending on composition and were characterized by SAXS, DSC, DMA, tensile stress–strain and fracture mechanics studies. SAXS, DSC, and DMA showed that microphase separation had occurred to give materials with a non-equilibrium morphology. DMA and tensile stress–strain studies showed the small strain properties to be very sensitive to the volume fraction of glassy material whereas the ultimate properties were dependent on chemical structure of the hard segment. Fracture properties were determined using the single-edge notch technique. In most cases ductile failure occurred with G_c > 2.5 kJ m^?2 and the fracture surfaces showed gross yielding and tearing. In the case of the copolyurea with the highest urea group content, brittle fracture occurred with G_c = 0.06 kJ m^?2.     

Influence of microstructure on micro-/nano-mechanical measurements of select model transparent poly(urethane urea) elastomers

Morphology of 4,4′-dicyclohexylmethane diisocyanate–poly(tetramethylene oxide) (PTMO)–diethyltoluenediamine based poly(urethane urea) (PUU) elastomers is investigated by atomic force microscopy (AFM) and compared with elastic modulus data measured from AFM-enabled indentation, dynamic nanoindentation (nanoDMA), and dynamic mechanical analysis (DMA). These measurements highlight the effect of altering the molecular weight (M_w) of PTMO, which is used as a soft segment (SS), on the microstructure. In particular, at SS M_w 2000 g/mol, a strong microphase-separated morphology is observed, whereas a phase-mixed dominated microstructure is noted in PUU with SS M_w of 1000 and 650 g/mol. These observations are also consistent with DMA tan δ results. Furthermore, instrumented impact indentation is also utilized for elucidation of dynamic damping characteristics in these PUUs.     

可再生原料为交联剂制备水性聚氨酯脲

以二苯基甲烷二异氰酸酯(IPDI)、二羟甲基丙酸(DMPA)为硬段,聚氧化丙烯二元醇(GE210)为软段,乙二胺(EDA)为扩链剂,制备了具有良好分散性的阴离子水性聚氨酯脲(PUU)分散液。并用可再生的氧化玉米淀粉对其进行了交联改性。测试结果表明,加入氧化交联淀粉后,水性PUU分散液的表面张力增加,成膜后的力学性能得到改善。同时随氧化淀粉用量的增大,水性PUU膜的拉伸强度也逐渐增大。     

Properties and phase segregation of crosslinked PCL‐based polyurethanes

Polyurethane (PU) films were prepared from different types of poly(ε‐caprolactone) glycols and hexamethylene diisocyanate without using any other ingredients such as solvent, catalyst, or chain extender. Polymers were stabilized by crosslinking formed as allophanate and/or biuret linkages during the curing process. The effects of different components on the product properties such as chemical structure, microphase segregation, mechanical strength, thermo‐mechanical, thermal properties, and surface hydrophilicities were investigated by FTIR‐ATR, atomic force microscope, mechanical tester, dynamic mechanical analyses, thermogravimetric analyzer, differential scanning calorimetry, and contact angle measurements. Phase separation of hard and soft segments significantly varied depending on the type and molecular weight of diol and triol. Films containing urethane‐urea bonds displayed the maximum phase separation and the highest mechanical strength. Polyols having higher molecular weight increased hydrophilicity while urea bonds caused a reverse effect resulted by bidentate hydrogen bonds. Results showed PUs with various properties can be synthesized via environmentally friendly process without using any solvent or catalyst. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39758.     

Synthesis and characterization of polyurethane urea acrylates: Effects of the hard segments structure

A series of poly(ester‐urethane‐urea) acrylates were synthesized using poly(ethylene adipate) diol (PEA), 4,4′‐diphenyl methane diisocyanate (MDI), different diamines and acrylic acid. On the basis of IR, stress–strain, thermogravimetric, and differential scanning calorimetry measurements of their cured materials, relations between their structure and physical properties were investigated systematically. The properties were compared with a polyurethane acrylate (PUA) elastomer in which the variable was the diamine modification. The mechanical analysis indicated that, when the short chain of diamine was used, the strength and strain at break of the polymer was enhanced. The thermal stability and the glass transition of PUA increased with increased of diamine chain. The crosslinking process depresses crystallization of the soft segments and can be used to obtain protective films and finishing materials for the leather industry. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Preparation and water resistance of crosslinked waterborne polyurethaneurea

Abstract

Two series of cross-linked polyurethaneurea (PUU) aqueous dispersions with polyoxypropylene glycerol and pentaerythritol as internal cross-linking agents were prepared and characterised. The results revealed that in comparison with the uncross-linked one, the cross-linked PUU films exhibited excellent waterproof performance and mechanical properties. The amount of water absorption was as low as 2?5 wt-%, the contact angle of water on the surface of this kind of film was as high as 96°, and the tensile strength was as high as 42?8 MPa. The cross-linked PUU films with polyoxypropylene glycerol and pentaerythritol as cross-linked agents showed different properties at the same cross-linking agent content. The prepared triol-cross-linked or tetra-cross-linked PUUs had great potential application in meeting the highly diversified demands in modern technologies such as coatings, leather finishing, adhesives, sealants, plastic coatings and wood finishes, where high water resistance and durability were required.