Modified polyurethane with a covalent bond of dye molecule

In this article, we have successfully synthesized polyurethanes (PUs) with a covalent bond of dye molecule via a coupling agent of epichlorohydrin. The structure is proven by infrared (IR) spectra, which exhibits the absorption peak of dye molecule, as we expected. The dye‐grafted polyurethanes were used to evaluate their inherent viscosity, mechanical, and thermal properties and, also, their dyeing behavior. For the inherent viscosity, the PUs with the grafting of the dye molecule demonstrate a lower value of viscosity than those without grafting of the dye molecule. The tensile strength is found to decrease with the grafting of the dye molecule due to the further separation of intermolecular distance of the grafted PUs. But the elongation at break is increased with the grafting of the dye molecule. In consideration of the thermal properties, PUs with the grafting of dye molecule exhibit higher T_gh than those without dye molecule. However, their T_gs and T_ms of soft segment between dyed and undyed PU seem to be similar. For dye migration property, the PUs with the grafting of dye molecule are proven to be much lower thermal migration values (Mp%) than those of simple mixing of PU and dyestuff. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 245–253, 1999     

Biocidal polyurethane and its antibacterial properties

The antimicrobial finishes on the cotton fabrics has been known and reported recently. Particularly, the reactive-antimicrobial finishes are the most attractive. In this study, we synthesized three types of polyurethane (PU) polymers; type A (molecular weight of polytetramethylene glycol (PTMG) is 2000), type B (molecular weight of PTMG is 1000), and type C (molecular weight of PTMG is 650). Firstly, the PU prepolymers were prepared by reacting PTMG with 4,4′-diphenylmethane diisocyanate (MDI), then were extended with diethylenetriamine (DETA) (or DETA/hydrazine mixture) to form the PU polymer. The polymer was then grafted with epichlorohydrin and further reacted with different amounts of biocide (QAS) to form biocidal active PU quaternary ammonium salts. The biocidal properties of the PU films were evaluated by the agar plate and the shake flask method. From the experimental results, it demonstrates that these films and finished fabrics exhibit a high biocidal activity against Staphylococcus aureus. The biocidal activity is found to increase with the amount of QAS. After rinsing with water, the biocidal characteristics of these films and finished fabrics remain. From IR spectra, PU films with covalent bond of QAS show an absorption peak at 2300 cm⁻¹, which corresponds to the presence of silicon in QAS. For the mechanical properties, the PU films with QAS sustain the mechanical properties in spite of the increasing amount of grafted QAS.     

Modified polyurethane with improvement of acid dye dyeability

This article concerns the modification of polyurethane using polyamide 6,6 prepolymer to improve the dyeability properties of the polyurethane copolymer with acid dye. First, the carboxyl‐terminated polyamide 6,6 prepolymer was synthesized from adipic acid and 1,6‐diaminohexane. The isocyanate‐terminated polyurethane prepolymer was also synthesized from polytetramethylene glycol and 4,4′‐diphenylmethane diisocyanate in N,N‐dimethylformamide. The polyurethane prepolymer was then extended with a mixture of 1,4‐butanediol and the polyamide 6,6 prepolymer (molar ratios of 1,4‐butanediol to prepolymer being 100%, 75%, 50%, and 25%, respectively). Finally, the poly(urethane–amide) copolymers were dyed with acid dyes. The chemical, physical, and the dyeing properties of the poly(urethane–amide) coploymers are discussed. From the experimental results, it is found that the inherent viscosity of poly(urethane–amide) coploymers is increased with the increasing amount of polyamide content. The structure is proven by infrared spectra, which exhibits the absorption peaks of urethane and amide groups as we expected. From the differential scanning calorimetry measurements, it is found that the poly(urethane–amide) coploymers have two‐phase structures and good phase separation. There are four transition temperatures (T_gs, T_gh, T_ms, and T_mh), but only those copolymers in PTMG 2,000 series possess T_ms. Moreover, the T_gs is found to change with the length of soft segment, and the T_gh is increased with the increasing amount of polyamide content. Also, the dyed copolymers exhibit higher T_gh than those without dyeing of dye molecule, but the T_gs is not obviously changed. For mechanical properties, it is indicated that both the modulus and the strength of the coploymers are higher than those of unmodified polyurethane, but they are lowered after being dyed with dye molecule due to further separation of intermolecular distance of the dyed polyurethanes. For dye uptake in dyeing properties, it is found to increase with increasing amount of polyamide content. For dye fastness, the dyed copolymers exhibit higher grade of water fastness than that of unmodified polyurethane. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1397–1404, 2003     

Silicon‐containing anionic water‐borne polyurethane with covalently bonded reactive dye

A silicon‐containing water‐borne polyurethane (PU) polymer with hydroxyl side groups was synthesized that was stable in basic conditions and also capable of reacting with a reactive dye to form a covalently bonded dye molecule. The silicon‐containing anionic water‐borne PU prepolymer was synthesized from H₁₂‐4,4′‐diphenylmethane diisocyanate (H₁₂‐MDI), polytetramethylene glycol, polydimethylsiloxane (PDMS), 2,2′‐bis(hydroxymethyl), propionic acid (anionic centers), and triethyleneamine using the prepolymer mixing method. Water was then added to emulsify and disperse the resin to form an anionic water‐borne PU prepolymer. N‐(2‐Hydroxyethyl ethylene diamine) (HEDA) was used to extend the prepolymer to form a water‐borne PU polymer with a side chain of hydroxyl groups, which can further react with the reactive dye to form a dyed PU. The reactive dye of chlorosulfuric acid esters of sulfatoethyl sulfones can react with the water‐borne PU polymer. Behaviors of alkali resistance and dyeing properties were observed. In consideration of thermal properties, the dye‐grafted PU polymers exhibited lower glass‐transition temperatures for soft segments and hard segments than those without dye. Concerning mechanical properties, it was found that the modulus and the strength of the dyed PU polymers decreased with grafting of the dye molecule, but elongation at break was increased. The alkali resistance increased with PDMS content. For dye‐uptake properties, the percentage of dye grafting was over 90%. Also, the dye‐grafted PU exhibited a lower percentage of dye migration than that of polymers with ethylene diamine instead of HEDA as a chain extender, and showed greater colorfastness to light. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2045–2052, 2003     

Synthesis of anionic water‐borne polyurethane with the covalent bond of a reactive dye

We successfully synthesized an anionic water‐borne polyurethane (PU) capable of reacting with a reactive dye to form a covalent bond with the dye molecule. The anionic water‐borne PU was synthesized and grafted with the reactive dye to form a dyed PU. First, the PU prepolymer was synthesized from 4,4′‐methylene bis(isocyanatocyclohexane), poly(tetramethylene glycol), 2,2′‐bis(hydroxymethyl) propionic acid (as an anionic center), and triethyleneamide (as a neutralizer). Then, pure water was added to emulsify and disperse the prepolymer to form an anionic water‐borne PU prepolymer. Finally, the extender N‐(2‐hydroxyethyl) ethylene diamine was used to extend the anionic water‐borne prepolymer to form a PU polymer with hydroxyl groups that could further react with the reactive dye molecule. With respect to the heating properties, the dyed PU polymers exhibited higher glass‐transition temperatures of the hard segment than those without dye molecules. However, neither the glass‐transition temperature of the soft segment nor the melting temperature of the soft segment varied in the presence of dye molecules, but they were changed with various chain lengths of the soft segment. As for the mechanical properties, the modulus and strength of the dyed PU polymers decreased because of the bulkiness of their dye molecules, but the breaking elongation increased. Moreover, the inherent viscosity decreased in the presence of the dye molecules. As for the dyeing properties, the percentage of dye grafting was greater than 90%. The dye‐grafted PU exhibited a lower percentage of migration than PU extended with ethylene diamine (without hydroxy groups) and also showed a higher grade of colorfastness to light. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 797–805, 2002; DOI 10.1002/app.10336     

The Influence of Macromolecular Structure and Composition on Mechanical Properties of Films Cast from Solvent‐Free Polyurethane/Acrylic Hybrid Dispersions

Polyurethane (PU) /acrylic dispersions are of great commercial interest due to the synergetic combination of the PU and acrylic polymers. In this work, a series of PU/acrylic dispersions is synthesized by a solvent‐free technique and the influence of colloidal structure, grafting between the two polymers, and the nature of the two polymer phases themselves on the mechanical properties of films cast from the dispersions is explored. TEM analysis shows that the particles have a PU shell/acrylic core structure which is translated into the morphology of films cast from the dispersions. This particle/film morphology leads to the acrylic copolymer acting as a filler material and allows high T_g copolymers to be employed, leading to films with very high mechanical strength. Grafting of the PU and acrylic phases leads to increased compatibility but has little effect on the mechanical properties which are largely determined by the hardness of both the diol used in the PU synthesis and more importantly the acrylic (co)polymer composition. This work allows us to propose a series of design principles in order to synthesize PU/acrylic hybrids with controlled mechanical properties.     

Nanotailoring of polyurethane adhesive by polyhedral oligomeric silsesquioxane (POSS)

The development and commercialization of nanoparticles such as nanoclays (NCs), carbon nanotubes (CNTs) and polyhedral oligomeric silsesquioxanes (POSS) offers new possibilities to tailor adhesives at the nanoscale. Four types of POSS, with reactive mono-functional groups of isocyanatopropyl, glycidoxypropyl, aminoethyl and non-reactive octaphenyl, were incorporated in concentrations of 1, 3 and 5 wt% into a polyurethane (PU)-based adhesive. Thermo-mechanical bulk properties were studied using dynamic mechanical analysis (DMA). Adhesive properties were characterized in shear and peel modes. Atomic force microscopy (AFM) was used to study the nanoscale morphology. DMA measurements indicated that the neat PU possessed a glass transition temperature (T _g) of ≈ 30°C. The T _g of PU/POSS-glycidoxypropyl nanocomposite adhesive increased gradually with POSS concentration to 50°C for 5 wt%. PU/POSS-octaphenyl nanocomposite adhesive exhibited an increased T _g by 10°C for 5 wt%. The incorporation of POSS-isocyanatopropyl in the PU had no effect on the T _g. With respect to shear properties of POSS-octaphenyl-, POSS-isocyanatopropyl- and POSS-glycidoxypropyl-based PU nanocomposite adhesives, shear strength improved by 230, 178 and 137%, respectively, compared to neat PU. POSS-aminoethyl exhibited lower shear and peel strengths, while POSS-isocyanatopropyl provided the best balance of both higher shear and peel strengths compared to neat PU. It was concluded that the grafted functional group on the POSS and its reactivity with the PU network components were the decisive factors with respect to the thermo-mechanical, morphological and adhesive properties of the resulting nanocomposite adhesives. Consequently, the POSS/polyurethane based nanocomposite adhesives could be tailored for a large range of applications.     

Synthesis and use of hydroxyl telechelic polybutadienes grafted by 2‐mercaptoethanol for polyurethane resins

The grafting of hydroxy telechelic polybutadienes (HTPBD) by 2‐mercaptoethanol to saturate 1,2‐double bonds which enabled an increase of the  OH functionality of HTPBD is presented. The functionalities of the virgin and grafted HTPBD were characterized both by ¹H‐NMR after silylation of the hydroxy end groups and the consumption of the mercaptan was determined by iodine titration. The radical addition of 2‐mercaptoethanol to HTPBD was not complete, which is not acceptable for an industrial application. Hence, the excess of mercaptan was reacted to allyl alcohol, leading to a new short telechelic diol able to be incorporated in the polyurethane (PU) network as a chain extender. This PU was prepared by addition of hexamethylene diisocyanate to both these diols. The thermal (glass transition, T_g, and decomposition temperatures), physical (gel time and viscosity), and mechanical (Shore hardness) properties were assessed. It was noted that the higher the hydroxyl functionality, the greater the Shore hardness, the viscosity, and the modulus but the lower the gel time and the break elongation. However, no improvement of the thermal stability was observed with the use of grafted HTPBD in PU resins. Their T_g's were observed to undergo a slight increase (of 4°C) in the case of PU prepared from Poly BD R45 HT® in contrast to that noted from Poly BD 20 LM® (20°C), showing a lower phase segregation in that latter case. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1655–1666, 2000     

Effect of molecular weight on shape memory behavior in polyurethane films

Understanding the relationship between the number‐average molecular weight (M_n) and the shape memory behavior of polymers is crucial for a complete picture of their thermomechanical properties, and hence for the development of smart materials, and, in particular, in textile technology. We report here on the study of shape memory properties as a function of M_n of polymers. Shape memory polyurethanes (SMPUs) of different M_n were synthesized, with various catalyst contents or molar ratio(r = NCO/OH) in the composition. In particular, two types of SMPU, namely T_m and T_g types according to their switch temperature type, were synthesized to compare the influence of M_n on their shape memory behavior. X‐ray diffraction, differential scanning calorimetry, dynamic mechanical analysis, and shape memory behavior results for the SMPUs are presented. The results indicate that the melting temperature (T_m), the glass transition temperature (T_g), the crystallinity, and the crystallizability of the soft segment in SMPUs are influenced significantly by M_n, before reaching a critical limit around 200 000 g mol^?1. Characterization of the shape memory effect in PU films suggests that the T_m‐type films generally show higher shape fixities than the T_g‐type films. In addition, this shape fixity decreases with increasing M_n in the T_g‐type SMPU, but the shape recovery increases with M_n in both types of SMPU. The shape recovery temperature, in contrast, decreases with M_n as suggested by the result of their thermal strain recovery. It is concluded that a higher molecular weight (M_n > 200 000 g mol^?1) is a prerequisite for SMPUs to exhibit higher shape recovery at a particular temperature. Copyright © 2007 Society of Chemical Industry     

Characterization of the relaxation transitions in toluene diisocyanate-based polyurethanes with poly(propylene glycol) as the soft segment by thermally stimulated current depolarization with relaxation mapping analysis

Thermal relaxation transitions of toluene diisocyanate (TDI)-based polyurethanes (PU) were characterized by the thermally stimulated current (TSC) technique with verification data from the relaxation mapping analysis (RMA) measurement. TDI-based PU elastomers with poly(propylene glycols) (PPG) as the soft segment and methylene-bis-orthochloroaniline (MOCA) as the hardener, showed three relaxation transitions, (1) a subglass transition (T_g) of the terminal groups occurred near −135°C; (2) the T_g; and (3) a global transition occurred above the T_g (assigned as T_global transition). The temperature of T_g of PU as expected was varied by the chain length and attributed by the motion of an urethanic chain dominated by the soft segment and may also associate in the cooperative movement with the hard segment. The T_global transition appearing above the T_g was identified and attributed to the global transition in the macromolecule scale and was supported by the tangent plot of the dynamic mechanical analyzer (DMA) measurement. The TSC measurement on thermal characteristic transitions of TDI-based PU provided a whole range of thermal transitions including a sub-T_g, the T_g (observed by DSC) to a global transition (may be observed by DMA) with the ease of sample preparation in one single measurement. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 527–545, 1999     

The temperature-sensitive water vapor permeation control of polyurethane membrane using the graft-polymerized poly(N-isopropylacrylamide) and the impact on the tensile strength and shape recovery effect

Poly(N-isopropylacrylamide) (poly(NIPAM)) was grafted onto polyurethane (PU) using a graft-polymerization method to develop a thermo-responsive PU and to investigate the impact on cross-link density, solution viscosity, soft segment thermal transitions, tensile properties, shape memory effect, and water vapor permeation through PU membrane. The soft segment crystallization peak sharply decreased with the increase in NIPAM content, whereas the glass transition temperature (T_g) slightly increased with the increase of NIPAM content. The breaking tensile stress rapidly increased with the increase in NIPAM content due to the cross-linking effect between the grafted poly(NIPAM) chains, whereas the strain at break did not significantly decreased as the NIPAM content increased. The shape recovery at 10°C rapidly increased from 46.9% for plain PU to above 90% after the grafting of poly(NIPAM) onto PU, and the shape retention at ?25°C slightly decreased with the increase in NIPAM content. Finally, the grafting of poly(NIPAM) onto PU demonstrated the temperature-responsive control of water vapor permeation through PU film due to the conformational change of the grafted poly(NIPAM) with the increase of temperature and the potential applications of the resulting PUs are discussed.     

Chemorheology and thermomechanical characteristics of benzoxazine‐urethane copolymers

In this research, processability and some important thermomechanical properties of polybenzoxazine (BA‐a) modified with a highly flexible urethane elastomer (PU) are discussed. This copolymer has been reported to show synergy in its glass transition temperature and some mechanical properties thus provides a fascinating group of high temperature polymers with enhanced flexibility. The results reveal that a processing window of the BA‐a/PU mixtures is widened with the increasing urethane prepolymer fraction, that is, the liquefying temperature is lowered and the gel point shifted to higher temperature with the amount of the PU. Synergism in glass transition temperature (T_g) of this copolymer was clearly confirmed, i.e., T_g's of the BA‐a/PU alloys were significantly greater than those of the parent resins, i.e., BA‐a (T_g = 166°C) and PU (T_g = ? 70°C). In addition, flexural modulus was found to systemically decrease from 5.4 GPa of the neat polybenzoxazine to 2.1 GPa at 40% by weight of the PU. Flexural strength of the alloys also shows a synergistic behavior at the BA‐a/PU ratio of 90/10. Coefficient of thermal expansion of the polymer alloys were also found to show a minimum value at BA‐a/PU = 90/10. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Low-pressure plasma surface modification of polyurethane films with chitosan and collagen biomolecules

Polyurethane (PU) was synthesized using castor oil and a trade grade of hexamethylene diisocyanate, and then PU films were prepared for wound dressing applications. The PU films were then plasma treated with the low-pressure nitrogen plasma to functionalize with peroxide and hydroperoxide groups in order to attach with acrylic acid monomers. Therefore, the polyacrylic acid polymer branches were formed on the film surfaces. Carboxylic acid groups were activated by N-(3-dimethylaminopropyl)-N′-ethyl carbodiimide hydrochloride/N-hydroxysuccinimide and bonded with chitosan and collagen biomolecules. Untreated, nitrogen plasma treated, polyacrylic acid grafted, and finally chitosan and collagen-immobilized PU films were characterized by several tests. The tests included the attenuated total reflectance Fourier transform infrared spectroscopy, static contact angle, atomic force microscopy, scanning electron microscopy, fibroblast L929 cell culture, and antibacterial activity assay to evaluate their in vitro cytocompatibility. The results confirmed that chitosan and collagen were immobilized successfully on the PU surfaces. The chitosan-immobilized PU and collagen-immobilized PU improved the adhesion and proliferation of fibroblast cells compared to untreated PU films. The chitosan-modified PU films exhibit the best antibacterial properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47567.     

Synthesis,properties, and dyeing application of nonionic waterborne polyurethanes with different chain length of ethyldiamines as the chain extender

This study deals with the synthesis of some nonionic waterborne polyurethanes (PUs), using ethyldiamines of different chain length, such as ethylenediamine (EDA) and diethyltriamine (DETA), as the chain extender in the reaction, and examines the thermal properties, mechanical properties, and dyeing properties of the PU products and their blends. As far as each PU by itself is concerned, we found that the T_g of the one made with DETA is the highest, followed by that with EDA, and the one with 1,4‐butanediol (1,4‐BD) is the lowest. The PU made with 1,4‐BD as the chain extender has no T_m, while the two others, using diamines as chain extenders, have a clear T_m, the one with DETA being higher than that with EDA. However, the enthalpy data are just the opposite. The tensile strengths of the two PUs, made with diamines as the chain extender, are larger than that made with 1,4‐BD, but their respective elongation properties are just the opposite. A comparison within PUs made with diamines showed that the one made with EDA is greater in both strength and elongation categories than that made with DETA. However, the one made with DETA is far superior to both of those made with 1,4‐BD and EDA in their dye‐exhaustion ratio, color yield (K/S), fixation rate, and color fastness. In respect to the various PU mixtures that we examined, we found that both PUs synthesized with EDA or DETA as the chain extender would have their T_g's greatly increased by blending in some PU made using 1,4‐BD as the chain extender. Among them, in particular, a blend of PU, made separately with DETA and 1, 4‐BD as the chain extender, showed great improvements in both tensile strength and elongation and also demonstrated better dyeability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2824–2833, 2003     

Synthesis and Properties of Aqueous Polyurethane/Polytert-butylacrylate Hybrid Dispersions

Aqueous polyurethane/polytert-butylacrylate (PU/Pt-BA) hybrid dispersions were prepared by polymerizing tert-butyl acrylate monomers that were emulsified by the waterborne polyurethane dispersions. The waterborne polyurethane dispersions, which contained no volatile solvent, were prepared by the prepolymer mixing process. The structure characteristics and properties of the hybrid dispersions were studied. A particle sizer and a viscometer were used to examine the physical characteristics of the dispersions. A Fourier transform infrared spectrophotometer and a gel permeation chromatograph were used to examine the structure of the hybrid composites. The thermal and mechanical properties were examined by a dynamic mechanical analyzer, a thermogravimetric analyzer, and an abrasion resistance tester. When the amount of ionic PU emulsifiers maintains constant, the average particle diameter and viscosity of the PU/Pt-BA hybrid dispersion become larger as more t-BA monomer was added and polymerized. As compared to the pure PU and Pt-BA polymers, the shifting of two T_gs in the composite toward each other may imply the improved compatibility between PU and Pt-BA through the hybridization process used in this study. The Pt-BA enhances the thermal and abrasion resistances of the PU/Pt-BA composites.     

Polymeric carbon nanocomposites from multiwalled carbon nanotubes functionalized with segmented polyurethane

Multiwalled carbon nanotubes (MWNT) were functionalized with segmented polyurethanes (PU) by the “grafting to” approach. Raman and X‐ray photoelectron spectroscopy (XPS) spectra show that the sidewalls of MWNTs have been functionalized with acid treatment, and the amount of COOH increases with increasing acid treatment time. FTIR and X‐ray diffraction (XRD) spectra confirm that PU is covalently attached to the sidewalls of MWNTs by esterification reaction. Similar to the parent PU, the functionalized carbon nanotube samples are soluble in highly polar solvents, such as dimethyl sulfoxide (DMSO) and N,N‐dimethylformamide (DMF). The functionalized acid amount and the grafted PU amount were determined by thermogravimetric analyses (TGA). Comparative studies, based on SEM images between the PU‐functionalized and chemically defunctionalized MWNT samples, also reveal the covalent coating character. Dynamic mechanical analysis (DMA) of nanocomposite films prepared from PU and PU‐functionalized MWNTs show enhanced mechanical properties and increased soft segment T_g. Tensile properties indicate that PU‐functionalized MWNTs are effective reinforcing fillers for the polyurethane matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Differential scanning calorimetry analysis of silicon‐containing and phosphorus‐containing segmented polyurethane. I—Thermal behaviors and morphology

This article investigated thermal transition and morphology utilizing differential scanning calorimetry (DSC), which was performed on silicon‐containing and phosphorus‐containing segmented polyurethane (Si‐PU and P‐PU). The hard segments of those Si‐PU and P‐PU polymers investigated consisted of 4,4′‐diphenylmethane diisocyanate (MDI) and diphenylsilanediol (DSiD), MDI, and methylphosponic (MPA), respectively. The soft segment of those polymers comprised polytetramethylene ether glycol, with an average molecular weight of 1000 or 2000 (PTMG 1000 and PTMG 2000, respectively). Several thermal transitions appeared for on the Si‐PU and P‐PU polymers, reflecting both the soft‐segment and hard‐segment phases. The Si‐PU and P‐PU polymers with a lower hard‐segment content exhibited a high degree of phase separating as indicated by the constancy of both the soft‐segment glass transition temperature (T_gs) and the breadth of transition zone (ΔB). The polymers in which PTMG 2000 was used as the soft segment generally exhibited a crystalline melting endotherm about 10°C, while crystallization usually disappeared upon melt quenching. The hard segments of the Si‐PU and P‐PU polymers displayed multiple endotherms. The first endotherm was related to a short‐range ordering of the hard segment domain (Region I), and the second endotherm was ascribed to a long‐range ordering of the domain (Region II). The wide‐angle X‐ray demonstrated that the structure in Region I and Region II was almost completely amorphous. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3489–3501, 2001     

Mechanical,thermal, and electric properties of polyurethaneimide elastomers

Linear polyurethaneimide elastomers (PUI) were obtained from polyether- or polyester-diols, diphenylmethane diisocyanate or bitolylene diisocyanate and pyromellitic acid dianhydride. It was found that these polymers have considerably better mechanical properties than typical linear polyurethanes (PU). The elastic modulus and stress at break increase with contents of the hard polyimide segments. The softening temperatures and thermal stability of the PUI at 500°C were higher than the ones of PU with similar hard segment contents. Electric properties of PUI were close to the ones of conventional PU. It was shown that cellular PUI had considerably lower dielectric constant. T_g's of the soft segments PUI were less than T_g's corresponding to PU. It is connected with greater phase separation of the hard imide segments from the soft polyether– or polyester–urethane matrix.     

Influence of hard segments of polyurethane on cell growth

Polyurethanes (PU) with suitable soft segments have been found to be good blood-compatible polymers and have attracted much attention recently. In this study, various molar amounts of 4,4′-methylene bisphenyl isocyanate reacted with poly(tetramethylene oxide) were synthesized to explore the optimal ratio of hard/soft segments for cell attachment and proliferation in in vitro systems. Differential scanning calorimetry and dynamic mechanical analysis were used to determine the physical properties, hydrogen bonding index (HBI) and transmission electron microscopy to observe the phase-separation phenomena in the materials, and 3T3 fibroblast to evaluate the dependence of the cell proliferation at 37°C on the material properties. Our results show that cell attachment and proliferation are closely related to the cell growth surface, which in turn is controlled by (1) the ratio of hard to total segment concentration and (2) the recrystallization temperature (T_c) of PU. To obtain a good cell growth surface, the ratio of hard to total segment concentration is found to be between 0.4 and 0.6, and HBI is between 1.5 and 2.1. Furthermore, when the T_c of PU is near the physiology temperature, a stable surface for cell growth can be provided. The shorter molecules in the soft segment region can rearrange the molecular chain at 37°C.     

Energetic studies on epoxy–polyurethane interpenetrating polymer networks

A blend system prepared from epoxy resin (EP) and polyurethane (PU) was investigated in terms of glass-transition temperature (T_g), contact angle, mechanical interfacial, and mechanical properties. Deionized water and diiodomethane were chosen as the angle testing liquids. In this work, the models of Owens–Wendt and Wu, using a geometric mean, were studied to analyze the surface free energy of the EP/PU blend system. Fourier transform infrared (FTIR) spectroscopy was employed to investigate the intermolecular hydrogen bonding and functional group changes. The impact test was carried out at room and cryogenic temperatures to determine the low-temperature performance of PU. As a result, mechanical interfacial and mechanical properties give a maximum value at 40 phr of PU, and the deviation of T_g of EP/PU was the closest at 40 phr of PU. Thus it is concluded that EP and PU have the best compatibilities at this ratio. Furthermore, the specific (or polar) component of the surface free energy of the blend system was largely influenced on the addition of the PU, resulting in increasing the critical stress intensity factor (K_IC) and the impact strength for the excellent low-temperature performance. These results could be explained by means of improvement of hydrogen bonding between the hydroxyl group in EP and isocyanate group in PU. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 775–780, 2001