Bending‐electrostrictive response of polyurethane films subjected to a reversed electric field

This study dealt with the bending‐electrostrictive response of a polyurethane film, which was a promising candidate for a material to be used in polymer actuators. The film bent under an electric field (2.5 MV/m). However, when the field polarity was reversed, the bending direction curiously did not change. To clarify the mechanism of this behavior, we measured the space charge distribution in the film. The measurement showed a pair of charges (induced charge on an electrode and space charge in the film) on one side of the film during the application of the field. However, when the field polarity was reversed, the location of the charges did not change. The charges were assumed to be the cause of the bending. Therefore, we concluded that the bending direction did not change despite the reversed field because the location of the charges did not change. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3644–3650, 2004     

Thermal decomposition of energetic thermoplastic elastomers of poly(glycidyl nitrate)

Energetic thermoplastic elastomers (ETPEs) are futuristic binders for propellant/explosive formulations. Poly(glycidyl nitrate) (PGN)‐based ETPEs have excellent performance, including a high energy and high oxygen content. PGN‐based ETPEs were synthesized on PGN as a soft segment and hexamethylene diisocyanate extended 1,4‐butanediol as a hard segment by a prepolymerization method. The thermal behavior of the PGN‐based ETPEs was investigated by thermogravimetric analysis (TGA) and derivative thermogravimetry. A fitting strategy was adopted to study every stage of decomposition. The results show that the ETPEs had four main decomposition processes, and the peaks of each stage were at 212, 262, 322, and 414°C. The gas products were tested by TGA/Fourier transform infrared spectroscopy/mass spectrometry, and the main gas products of the samples were N₂O, CH₂O, C₂H₄O, and CO₂. The previous results indicate the proposed mechanism of thermal decomposition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40965.     

Fracture of an epoxy polymer containing recycled elastomeric particles

The fracture behavior of elastomer-modified epoxy was investigated using compact-tension geometry. The elastomeric modifiers included a liquid carboxyl-terminated butadiene acrylonitrile and solid rubber particles of different sizes which were obtained from recycled automobile tires. When used with solid rubber alone, no significant improvement in the fracture toughness was observed. However, when used in combination with the liquid rubber modifier, it was observed that the fracture toughness of these hybrid epoxies was higher than that of those toughened with liquid rubber alone. This synergistic effect is explained in terms of crack deflection and localized shear yielding. Furthermore, we observed a slight improvement in the fracture toughness as the size of the solid rubber particles increased. Although using a combination of both reactive rubber liquids and solid rubber particles as toughening agents had been investigated previously, in this study, the solid rubber particles used were from recycled rubber tires. Therefore, we have clearly demonstrated an application of producing high-quality engineering epoxy systems using toughening modifiers that are relatively low in cost and created higher-value products for recycled solid rubber. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 271–277, 1997     

Degradation behavior of an ultraviolet and hygrothermally aged polyurethane elastomer: Fourier transform infrared and differential scanning calorimetry studies

The degradation behavior of an elastomeric polyurethane (PU) was investigated with accelerated ultraviolet (UV) and hygrothermal (HT) techniques. Samples were subjected to UV exposure and HT conditions for 3 or 5 months and were removed in 1‐month intervals from the test chambers. Their chemical structure was evaluated with Fourier transform infrared (FTIR) spectroscopy. The thermal transitions of the aged samples were evaluated with differential scanning calorimetry (DSC). Both FTIR and DSC results showed no evidence of significant structural damage to the HT‐aged PU throughout exposure. FTIR analysis of the UV‐aged samples showed a noticeable change in the chemical structure of the polymer after 1 month of UV exposure. The results from DSC correlated with the FTIR analysis of the UV‐aged samples. Spectroscopic and thermal analysis of the aging of the PU samples was correlated to mechanical analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Semi-interpenetrating polymer networks from castor oil-based polyurethanes and chlorinated rubber

Semi-interpenetrating polymer networks (semi-IPNs) were prepared by crosslinking castor oil in the presence of chlorinated rubber. Crosslinking in toluene solution was effected with 2,4-toluene diisocyanate or hexamethylene diisocyanate at various NCO/OH ratios. The semi-IPNs were obtained as tough films and were characterized by their mechanical, thermal, morphological and electrical properties.     

Ozone cracking and flex cracking of crosslinked polymer blend compounds

Ozone cracking and flex cracking of crosslinked elastomer blends of brominated isobutylene/para‐methylstyrene copolymer (BIMSM) and unsaturated elastomers, such as polybutadiene rubber (BR) and natural rubber (NR), are studied. This saturated BIMSM elastomer, which is a terpolymer of isobutylene, para‐bromomethylstyrene, and para‐methylstyrene, functions as the ozone‐inert phase of the blend. Ozone cracking is measured by the failure time of a tapered specimen under a fixed load in a high severity ozone oven, whereas flex cracking is ranked by the De Mattia cut growth. The ozone resistance of BIMSM/BR/NR blends is compared to that of a BR/NR blend (with or without antiozonant) at constant strain energy densities. The effects of the BIMSM content in the blend, the structural variations of BIMSM, and the network chain length between crosslinks on these two failure properties, which are important in crosslinked compounds for applications in tire sidewalls, are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2183–2196, 2007     

Carbon nanotubes‐filled thermoplastic polyurethane–urea and carboxylated acrylonitrile butadiene rubber blend nanocomposites

This article reports the preparation and characterization of multiwalled carbon nanotubes (MWCNTs)‐filled thermoplastic polyurethane–urea (TPUU) and carboxylated acrylonitrile butadiene rubber (XNBR) blend nanocomposites. The dispersion of the MWCNTs was carried out using a laboratory two roll mill. Three different loadings, that is, 1, 3, and 5 wt % of the MWCNTs were used. The electron microscopy image analysis proves that the MWCNTs are evenly dispersed along the shear flow direction. Through incorporation of the nanotubes in the blend, the tensile modulus was increased from 9.90 ± 0.5 to 45.30 ± 0.3 MPa, and the tensile strength at break was increased from 25.4 ± 2.5 to 33.0 ± 1.5 MPa. The wide angle X‐ray scattering result showed that the TPUU:XNBR blends were arranged in layered structures. These structures are formed through chemical reactions of ? NH group from urethane and urea with the carboxylic group on XNBR. Furthermore, even at a very low loading, the high degree of nanotubes dispersion results in a significant increase in the electrical percolation threshold. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40341.     

Development of an intermediate layer for multilayer hoses used in turbo lines of motor vehicles

Multilayer hoses for turbo lines can be produced by ethylene acrylic rubber (AEM) as the inner layer and peroxide cured ethylene propylene diene monomer (EPDM) as the outer layer. In such a case, the polar AEM should adhere well to the apolar EPDM to ensure proper functioning. In this work, new blends were developed and optimized to offer potential for using as intermediate bonding layers. Different compositions of dipolymer AEM/EPDM and terpolymer AEM/EPDM blends with and without maleic anhydride grafted EPDM (Ma‐g‐EPDM) as a compatibilizer were successfully prepared. Curing behaviors, as well as mechanical and thermal properties of the blends were investigated in detail. The effects of the compatibilizer addition were also explored by dynamical mechanical analysis, DeMattia and scanning electron microscope. It is found that Ma‐g‐EPDM is more effective in terpolymer AEM containing blends. Additionally, 60/40:AEM/EPDM weight ratio is the most suitable proportion for turbo lines. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46525.     

Synthesis and characterization of biodegradable polyurethanes based on L‐cystine/cysteine and poly(ϵ‐caprolactone)

Tunable biodegradable polyurethanes (PUs) with favorable mechanical properties were synthesized from 1,6‐hexamelthylene diisocyanate (HDI) as the hard segment, poly(?‐caprolactone) (PCL) as the soft segment, and L ‐cystine ester as chain extender. The structure of PUs was confirmed by FTIR and ¹H‐NMR. The results of differential scanning calorimeter, thermogravimetric analysis, dynamic mechanical analysis, and tensile test revealed that the thermal and mechanical properties of PUs were strongly influenced by the molecular weight of soft segment PCL. In the presence of glutathione, the disulfide group cleaved into thiols, realizing the PUs degraded and the molecular weight decreased. For PU [550], it remained only 50% of the original M_w. Evaluation of cell viability demonstrated the nontoxicity of the PUs, which facilitated their potential in biomedical applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanical properties of crosslinked polyurethane elastomers based on well‐defined prepolymers

This article presents research findings for selected mechanical properties of polyurethane elastomers. The studied elastomers were synthesized with the prepolymer‐based method with the use of controlled molecular weight distribution (MWD) urethane oligomers and with the classical single‐stage method. Prepolymers with defined MWDs were obtained with the use of a multistage method, that is, step‐by‐step polyaddition. To produce elastomers, isocyanate oligomers were then crosslinked with triethanolamine, whereas hydroxyl oligomers were crosslinked with 4,4′,4′′‐triphenylmethane triisocyanate (Desmodur RE). The tensile strength of the obtained elastomers ranged from 1.0 to 7.0 MPa, the ultimate elongation approached 1700%, the Shore A hardness varied from 40 to 93°, and the abrasion resistance index fell within 15–140. The effects of the types of raw materials used, the chemical structures, the production methods, and the supermolecular structures on the mechanical properties of the obtained polyurethane elastomers were examined. When the obtained findings were generalized, it was concluded that the structural changes in the polyurethanes, which were favorable for intermolecular interactions, improved the tensile strength, hardness, and abrasion resistance of the materials and impaired their ultimate elongation at the same time. More orderly supermolecular structures and, therefore, superior mechanical properties were found for polyurethane elastomers produced with the prepolymer method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of fullerene derivatives on the gas permeability of thermoplastic polyurethane elastomers

In an effort to improve the gas barrier properties of thermoplastic polyurethane (TPU) elastomers, fullerene derivatives were added as fillers, and the resulting O₂ and CO₂ permeabilities were analyzed. The addition of 5 wt % polyhydroxylated fullerene {fullerenol [C₆₀(OH)_n] mixture, where n = 6–12} decreased the gas permeability by approximately 10–20%. According to the hole volumes computed with the results from positron annihilation lifetime spectroscopy, the addition of fullerene derivatives did not produce any changes in the hole volumes of the TPUs. Thus, the reduction in the TPU gas permeability was not caused by changes in the hole volumes. Instead, an inhibited diffusion of gas molecules by fullerene particles was deduced as the cause of the decrease in gas permeability from changes in the diffusion coefficient with temperature. The addition of urethanized fullerene, prepared through the chemical modification of fullerenol, markedly affected the TPU gas barrier properties. As compared to fullerenol addition, the gas barrier properties improved approximately fourfold for O₂ and approximately fivefold for CO₂. These results suggest that the dispersability of urethanized fullerene in TPU was higher than that of fullerenol. We found that the gas barrier properties were independent of the structure of polyol. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39986.     

Interchain crosslinkable polymer blends of polyurethane and polyacrylic elastomer (sulfur cure)

Blends of polyurethane and polyacrylic elastomers prepared by three different blending techniques have been studied in different blend ratios. The processability of the polyurethane elastomer was improved as a result of blending with the polyacrylic elastomer. The blending technique has a significant role in determining the physical properties of the blends. Improvement of physical properties was observed in the blends containing the interchain crosslink bonds. IR spectral analysis suggested the formation of interchain crosslink between the two elastomers phases on heat treatment, before the addition of any curatives. Thermal stability of the blends was also improved when preblending and preheating techniques were applied. The extraction of the single phase by solvent was also restricted to a significant extent for the preheated sample probably due to the interchain crosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 845–853, 2004     

Resistivity and Thermal Reproducibility of the Carbon Black and SnO2/Sb Coated Titanium Dioxide Filled Silicone Rubber Heaters

Summary: Flexible heaters were prepared by extruding platinum‐catalyzed silicone rubber compound with electroconductive carbon black (CB) and SnO₂/Sb coated titanium dioxide (TiO₂). Two types of acicular‐shaped TiO₂ with average particle sizes of 1.7 and 5.2 µm, and two types of spherical‐shaped TiO₂ with average particle sizes of 0.3 and 2.5 µm were selected. Thermoelectric switching phenomena were investigated for the silicone rubber/CB/TiO₂ system. Positive temperature coefficient (PTC) was significant when the acicular filler was added rather than spherical ones. Resistivity change and thermal reproducibility of the extruded heaters were also investigated by applying periodically AC voltage of 220 V. The heaters containing acicular‐shaped TiO₂ exhibited excellent electrical reproducibility.

Scanning electron micrograph of the fractured surface of the extruded composites.     

Characteristics and performance of electroactive paper actuator made with cellulose/polyurethane semi‐interpenetrating polymer networks

This article introduces a cellulose/polyurethane (PU) semi‐IPN‐based electroactive paper (EAPap) actuator. The fabrication process, bending actuation test, and its characteristics are explained. For the fabrication of cellulose/PU semi‐IPN EAPap actuator, cotton cellulose was dissolved into N,N‐dimethylacetamide (DMAc) and lithium chloride (LiCl) solvent system. PU prepolymer prepared by poly[di(ethylene glycol) adipate] and hexamethylene diisocyanate (HDI) was mixed with DMAc cellulose solution by stirring. The mixed solution was spin‐coated on a wafer and cured to form cellulose/PU semi‐IPN films using 1,1,1‐tris(hudroxymethyl)propane as the crosslinker. The characteristics of the cellulose/PU semi‐IPN film were investigated by FTIR, scanning electron microscopy (SEM), X‐ray diffraction pattern (XRD), and tensile test. The bending actuation performance of the actuator was evaluated in terms of free bending displacement with respect to the actuation frequencies, voltages, and humidity levels. It shows a good bending actuation at room humidity condition. The actuation principle of the actuator is also discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of water‐compatible antifungal polyurethane with grafted benzimidazole as the antifungal agent

We compared two series of benzimidazole (BI)‐grafted polyurethane (PU), one of which was water‐compatible, to compare their antifungal activities. The water‐compatible PU series had an additional 2,2‐bis(hydroxymethyl)propanoic acid group in the PU backbone. The water‐compatible PU series had a lower crosslinking density and tensile strength compared to the other PU series with increasing BI content. Although ordinary PU did not suppress fungal growth (Chaetomium globosum), the water‐compatible PU completely suppressed the growth even though it contained half as many BI groups. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41676.     

Evaluation by various experimental approaches of the crosslink density of urethane networks based on hydroxyl‐terminated polybutadiene

Crosslink density (CLD) is an important characteristic for elastomeric polymer networks. The mechanical and viscoelastic properties of the elastomers are critically dependant on the CLD. Several methods have been adopted for its determination, but swelling and stress–strain methods continue to be more popular because of the convenience associated with these techniques. In this article, the determination of CLD of allophanate–urethane networks based on hydroxyl‐terminated polybutadiene and toluene diisocyanate with swelling and stress–strain methods is reported. The Flory–Rhener relationship was applied to calculate CLD from the swelling data. CLDs were also calculated from the initial slope of the stress–strain curve (Young's modulus), Mooney–Rivlin plots, equilibrium relaxation moduli, and dynamic mechanical properties. A comparison was drawn among the values obtained with the various methods. Although the CLD values obtained from Mooney–Rivlin plots were slightly lower than those obtained from swelling data, the values obtained with Young's modulus and storage modulus were considerably higher. The values obtained with swelling and equilibrium relaxation moduli data were very close to each other. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3129–3133, 2007     

Effect of a small amount of sulfur on the physical and mechanical properties of peroxide‐cured fully saturated HNBR compounds

Sulfur can be used as crosslink coagent in unsaturated elastomer. In this work, a fully saturated HNBR with 39 wt % nitrile content was selected to investigate the effect of a small amount of sulfur acting as crosslink coagent on the physical and mechanical properties of peroxide‐cured vulcanizates. First, selective cleavage of polysulfide (? Sx? ) and monosulfide(? S? ) bond by combined thiol‐piperidine treatment were performed and the existence of poly/monosulfide bond in sulfur‐contained HNBR compounds was verified. Then, no‐filler HNBR compounds with various content of sulfur were investigated to detect the influence of sulfur on the crosslink density and cure kinetics. The MDR results showed that the crosslink density of HNBR compounds reduced only when the amount of sulfur is 0.25 phr and above. Besides, the curing rate of no‐filler HNBR compounds increased with the increasing of the amount of sulfur and reached a maximum at a dosage of 0.25 phr sulfur. Finally, physical and mechanical properties of fully formulated compounds were evaluated and it was found that the addition of small amounts of sulfur in fully saturated HNBR compounds could improve the dynamic properties of peroxide‐cured HNBR compounds remarkably but at a cost of slightly higher compression set values and a small loss in heat aging resistance. In a conclusion, small amount of sulfur can impart the peroxide vulcanizates some “sulfide properties” like dynamic property, tensile strength, but at the same time, due to the introduction of sulfur, some “peroxide vulcanizates property” like heat‐resistance property, hot air resistance were weakened slightly. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41612.     

Cure and scorch in the processing of ethylene‐propylene‐diene terpolymer (EPDM)

The objective of this work is to ascertain the characteristics of desirable (cure) and especially undesirable (scorch) crosslinking when carbon black filled ethylene propylene diene terpolymer (EPDM) is processed using different peroxide initiators. The mixing temperature and the nature of the peroxide initiator are crucial parameters affecting scorch (undesirably premature crosslinking) in this rubber. Processability and properties of EPDM prepared using various mixer set temperatures have been investigated. Dicumyl peroxide (Luperox DC), di(t‐butylperoxy) diisopropylbenzene (Luperox F), and 2,5‐dimethyl‐2,5‐di(t‐butylperoxy) hexane (Luperox 101) were used as crosslinking initiators. Higher mixing temperatures give shorter scorch times, greater scorch magnitudes, greater heterogeneities in crosslink spatial distribution and poorer tensile properties. However, extreme localization of the unwanted crosslinking at the rubber‐filler interface does have a beneficial effect. Luperox DC offers poorer processability and poorer resulting properties than do Luperox F and Luperox 101, due to its shorter half‐life and greater solubility in the rubber phase. This is the first time that the spatial heterogeneity of crosslinking and scorch has been related to the basic thermodynamics of 3‐component 2‐phase systems. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44523.     

Novel method for preparation of polyurethane elastomers with improved thermal stability and electrical insulating properties

A novel method was developed for the preparation of polyurethane with enhanced thermal stability and electrical insulation properties via the reaction of epoxy‐terminated polyurethane prepolymer (EPU) and poly(amic acid) (PAA). EPUs were synthesized from the reaction of glycidol with NCO‐terminated polyurethane prepolymers, which were prepared from the reaction of polycaprolactone‐based polyol (CAPA) of different molecular weights and some commercially available diisocyanates including hexamethylene diisocyante, toluene diisocyanate, and 4,4′‐methylene bis(phenyl isocyanate). PAA was prepared from the reaction of equimolar amounts of pyromellitic dianhydride and oxydianiline. The effects of PAA content, the nature of diisocyanate, and the molecular weight of CAPA on the mechanical, thermal, thermomechanical, and electrical properties of the final networks were investigated. The crosslink density of the samples was determined according to an equilibrium swelling method using the Flory–Rehner equation and was correlated to the structure of the final polymers. Gel content and activation energy of network formation in the absence and the presence of a tertiary amine catalyst were also studied. The results showed considerable improvement in the thermal, electrical, and mechanical properties compared to those of other common polyurethanes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1776–1785, 2007     

Preparation,hydrogen bonding and properties of polyurethane elastomers with 1,2,3-triazole units by click chemistry

Two kinds of diols containing 1,2,3-triazole units were synthesized through the azide-alkyne cycloaddition reaction between propargyl alcohol and 1,4-diazidobutane. One of the diols, (butane-1,4/1,5-diylbis[1H-1,2,3-triazole-1,4/1,5-diyl])dimethanol (BDTDO-1), containing 1,4/1,5-disubstituted 1,2,3-triazole regioisomers, was directly prepared under thermal condition without Cu(I) catalyst. The other diol, (butane-1,4-diylbis[1H-1,2,3-triazole-1,4-diyl])dimethanol (BDTDO-2), containing 1,4-disubstituted 1,2,3-triazoles, was prepared by Cu(I) catalyzed click chemistry. Then, two kinds of 1,2,3-triazole modified polyurethane elastomers (PUEs) were prepared from the reaction of 4,4′-methylenebis(phenyl isocyanate) and poly(tetramethylene ether) glycol, with BDTDO-1 or BDTDO-2 as the chain extender (CE). It was found that the introduction of 1,2,3-triazoles and their substitution positions had significant influences on the hydrogen bonding, thermal and mechanical properties of PUEs. Compared with the PUE prepared from 1,4-butanediol as the CE, the PUE containing symmetric 1,4-disubstituted 1,2,3-triazoles units in the main chains shows higher values of hydrogen bonding, physical crosslinking density, Young's modulus, tensile strength and melting temperature, while lower glass transition temperature, resulting from the rigid structure and the ability to form more hydrogen bonds. However, the introduction of asymmetric 1,4/1,5-disubstituted 1,2,3-triazole moieties decreases the values of hydrogen bonding, thermal and mechanical properties of PUE appreciably due to the destruction of the ordered structure of the hard segments.