Polyurethane Group Research Articles

Preparation and property evaluation of nanocomposites based on polyurethane‐modified epoxy/montmorillonite systems

AbstractMontmorillonite nanoclay and polyurethanes obtained from polyethylene glycol (PUR 400) and polyoxypropylene diol (PUR 1002) were used to enhance the mechanical properties of an epoxy resin. Maximum impact strength improvement was obtained with compositions containing 2% nanoclay and 10% PUR 400 as well as that with 1% nanoclay and 15% PUR 400, corresponding to 110% and 75%, respectively, in relation to the unmodified epoxy resin. Moreover, a 10‐fold increase was observed with respect to the flexural strain at break for the composition containing 15% PUR 1002 and 2% nanoclay. SEM micrographs have indicated that the mechanism of mechanical property enhancement is associated with increased yield of the epoxy matrix. Moreover, FTIR results showed that some chemical reactions have taken place between the hydroxyl groups of epoxy resin and the isocyanate groups of polyurethane, explaining partly the improvement in the mechanical properties of the polymer matrix. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:237–248, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20192

Investigation of adhesion of modern wound dressings: a comparative analysis of 56 different wound dressings

In the process of chronic wound care, adhesive wound dressings may cause pain and injury in the wound environment during dressing changes. At present, no standardized test procedures are available for the investigation of adhesion of wound dressings. Therefore, our study aimed to test the adhesion of different wound dressings on steel as well as on healthy skin. Within an open, comparative study, the adhesive areas of 56 wound dressings were investigated. The adhesives were categorized into acrylate (n = 23), silicone (n = 9), hydrocolloid (n = 17) and polyurethane groups (n = 7). Using an especially modified testing machine, the adhesion of the wound dressings was measured on steel as well as on the skin of healthy study participants, in compliance with the European EN 1939:2003 standard. The energy required to remove the wound dressings from human skin, was measured in Newton (N) and the following median values were obtained: hydrocolloid (2.25 N) > acrylate (1.14 N) > polyurethane (0.9 N) > silicone (0.7 N). The subjective pain intensity during the removal of the wound dressings was recorded using the visual analogue scale (VAS) with values ranging from 0 to 10. For hydrocolloid, it was 6.8, for acrylate 4.9, for polyurethane 3.1 and for silicone 2.5 points VAS. In comparison with human skin, the adhesion of wound dressings was significantly higher on steel (P < 0.0001), but was different for the different groups of wound dressings. Moreover, there was a statistically significant correlation between the adhesion and pain intensity (correlation coefficient 0.806; P = 0.01). The knowledge about the widely differing adhesion properties of different wound dressings on the skin of patients should nowadays be considered during the individual selection of the applied products. Based on these data, different types of wound dressings could be developed, guaranteeing a good adhesion and a low traumatic risk when removed.

Polyurethane and PTFE barriers for guided bone regeneration: A hismorfometric study in rabbits parietal bone

The purpose of this study was to evaluate the process of bone repair in surgical defects created in parietal bone of rabbits by the guided bone regeneration technique, using polyurethane (PUr) and PTFE barriers. The surface characteristics of the barriers in scanning electronic microscopic were also evaluated. In this research, 24 adult rabbits were used, 12 were in control group (C) and 12 were in experimental groups (right parietal – PUr group and left parietal – PTFE group). In the C group, the defect was filled only by blood clot. In the experimental groups, the PUr and PTFE barriers were positioned on the floor and on the surface of each bone defect. After 15, 30, 60 and 90 days, 3 animals in the C and 3 in the experimental groups were sacrificed and the defect bones were submitted to microscopic analysis. The results of the study showed no significant differences in the experimental groups, demonstrating quantitative and qualitative superiority bone fill and faster bone regeneration when compared to the C group. The physical barriers presented homogenous surface and no porosity. The PUr was biocompatible, osteoconductive and was not absorbed during the process of bone repair.

The effect of urethane and urea content on the gas permeation properties of poly(urethane-urea) membranes

The effect of urethane and urea contents on gas separation properties of the groups of polyurethane–urea membranes is studied. The membranes used in this study were prepared by polytetramethylene-glycol (PTMG) and isophorone diisocyanate (IPDI) prepolymers. The prepolymers were converted to final polymer using the designed proportion of 1,4-butane diol (BDO) and 1,4-butane diamine (BDA) as a chain extender. Five different BDO/BDA ratios were chosen in order to synthesize poly(urethane-urea)s with different urethane/urea linkage content. The prepared polymers were characterized and the permeability of gases through them was investigated. Results obtained by Fourier transform infrared spectrometer (FT-IR) and differential scanning calorimetery (DSC) indicate that by increasing the urea linkage in the polymers, the microphase separation of hard and soft segments increase. Study of the X-ray diffraction (WAXD) patterns confirmed that polyols may be arranged in small crystalline structures. Permeation measurements of polymers revealed that the permeability of gases decreases with increasing urethane content in the polymers and selectivity of gases decreases with increasing urea content. The solubility and diffusivity of gases indicate solubility domination of gas transport in these membranes. The results of permeability also show high amounts up to 128 Barrer (1 Barrer = 1 × 10 −10 [cm 3 (STP) cm/cm 2 s cm Hg]), and high selectivity for carbon dioxide with respect to nitrogen (CO 2/N 2: 27).

Influence of Nanosilica/Polyurethane Composite Coating on IR Effectiveness and Visible Light Transmission Properties of Polyethylene

Polyethylene (PE) film was coated with nanosilica-polyurethane layer using rod Mayer process. The nanosilica-polyurethane system was prepared by dispersing nanosilica (SiO2) powder into solvent borne polyurethane (PU) binder under vigorous stirring. Various compositions of nanosilica-polyurethane slurry were prepared. A battery of characterization procedures were used to study the properties of the nanocomposite coating. ATR FTIR confirmed the presence of functional groups of silica and polyurethane. The uniformity of silica dispersion was probed using scanning electron microscopy (SEM). With the introduction of nanosilica to polyurethane binder, the visible light transmittance and ultra-violet (UV) radiation of nanosilica-polyurethane system reduced with increasing nanosilica content and coating layer thickness. The PE coated with nanocomposite containing 14wt% nanosilica and with 8 µm coating thickness showed &gt;88% transmittance in the visible light region. Infrared (IR) effectiveness (between 7 μm to 13 μm wavelengths) measurements by FTIR also showed that nanosilica/polyurethane system coating on PE film surface greatly improved the infrared opacity properties of PE film.

Thermal stability of glued wood joints measured by shear tests

The thermal stability of glued wood joints is an important criterion to determine the suitability of adhesives in the field of engineered wood. During their product life, glued wood joints can be exposed to high temperatures in various ways (direct exposure to the sun, fire, etc.). Thereby the cohesiveness of the adhesive must not degrade. This raises the question of how the strength of bonding changes under thermal load. The current investigation covers the influence of temperature (T=20 to 220°C) on the shear strength of glued wood joints. Different adhesive systems were investigated. With increasing temperature, the shear strength of solid wood and also of glued wood joints decreased. There were big differences in thermal stability and failure behaviour between the adhesive systems as well as within the polyurethane group. The thermal stability of one-component polyurethane systems can be greatly varied by modifying their chemical structure. Well adapted one-component polyurethane adhesives reach a strength similar to that of phenol resorcinol resin.

Assessment of amniotic and polyurethane membrane dressings in the treatment of burns

As allograft and xenografts are not available in Islamic countries, amniotic membrane seems to be an effective alternative in the management of deep burns. Its proven bioactivities and modest price suggest that it might be superior to synthetic dressings. Forty-six patients were enrolled in this randomized, controlled clinical trial conducted in the Burn Unit at Suez Canal University Hospital, Ismailia, Egypt. All age groups and both gender were included in the study. Only patients with less than 50% total body surface area burned were included, thus minimizing the dropouts in both groups. All were either second or third degree. These patients were randomly assigned either to group I: amniotic membrane (Biomembrane) dressing, or group II: polyurethane membrane (Tegaderm) dressing. Those in group I demonstrated a significantly lower rate of infection and required less frequent dressing changes than those in group II. They also sustained less electrolyte and albumin loss. The rate of healing in the amniotic membrane group was significantly faster than in the polyurethane group. Furthermore, pain was significantly less when Biomembrane was used. Based on these findings, we recommend the use of lyophilized gamma-irradiated amniotic membrane as an effective alternative for allograft and xenografts in Islamic countries and the Jewish population.

The Use of Ultrasound to Assess the Thrombogenic Properties of Teflon and Polyurethane Catheters for Short-Term Use in Systemically Healthy Horses

The objective of this study was to establish an ultrasound scoring system to assess the degree of fibrin tag and clot formation associated with jugular catheters in horses. A second objective was to test the hypothesis that, in healthy horses undergoing short-term anesthesia, polyurethane (PU) catheters have a different ultrasound score compared with polytetrafluoroethylene (Teflon) catheters. Twenty-three systemically healthy horses requiring anesthesia were randomly assigned PU or Teflon catheters. The mean catheter dwell time was 5 hours. Ultrasound was used to examine the jugular vein before catheter placement, before catheter removal (mean, 4 hours 45 minutes), and approximately 24 hours after catheter insertion (mean, 24 hours 42 minutes). The repeatability of the ultrasound scoring system was assessed by producing a series of randomly ordered selected still images for independent evaluation by four radiologists on two separate occasions. The interobserver and intraobserver repeatability was determined using a weighted kappa statistic, with substantial intraobserver repeatability mean κ .77 (range, .59–.91) and moderate interobserver repeatability mean κ .53 (range, .33–.67). The proportion of positive bacteriologic cultures in the polyurethane (PU) and Teflon groups was compared using Fisher's exact test, with no significant difference ( P > .99) between the two groups. The distribution of the scores from the PU and Teflon groups was compared using the Mann-Whitney test, with no evidence of a difference between groups at the time of catheter removal ( P = .23) and 24 hours after catheter insertion ( P = .20). Further studies with a larger sample of systemically healthy horses are required to substantiate this preliminary finding.

Comparison of Tissue Reaction with Three Different Endografts Used for Exclusion of Carotid Artery Aneurysm in a Dog Model

To assess the efficacy and biocompatibility of balloon-expandable stainless-steel stents covered with various membrane types. Stents covered with biomembrane (ie, piglet greater omentum vein), polyurethane, or expanded polytetrafluoroethylene (ePTFE; n = 12 each) were implanted into the 36 bilateral carotid arteries of 18 dogs to treat 36 surgically created saccular side wall aneurysms. Treated dogs were administered anticoagulation therapy after stent implantation. Angiography was performed immediately after the procedure and at 2, 4, and 12 weeks. Aneurysm isolation, primary parent artery patency, acute thrombosis in the stent, and endoleak were investigated. Two dogs in each group were killed at each follow-up interval, the stent-implanted arteries were removed for light and electron microscopy, and aneurysm thrombosis, stenosis rate, and endothelialization progress were observed. Thirty-six stents were successfully placed and 36 aneurysms completely isolated, with no endoleaks revealed by immediate or follow-up angiography. The primary patency rates of the biomembrane-, polyurethane-, and ePTFE-covered stents were 91.7%, 50%, and 66.7%, respectively. At 12 weeks, a luminal narrowing of 24.27% +/- 6.23% was seen in the biomembrane group, compared with 30.78% +/- 1.41% (P = .025) in the polyurethane group and 20.56% +/- 7.22% (P = .247) in the ePTFE group. All treated aneurysmal pouches had filled with thrombi and stent wires were encased by extended neointima. Endothelialization in the biomembrane group had begun by 2 weeks, which was earlier than in the polyurethane or ePTFE groups. All three stent-grafts successfully excluded carotid aneurysms. Biomembrane-covered stents showed better primary patency and less intimal hyperplasia than polyurethane- or ePTFE-covered stents.

セグメントポリウレタンにおけるソフトセグメント成分の変化に伴う染色性の変化

The aim of this study is to clarify the dyeing behavior with acid dyes in the segmented polyurethanes with soft segments composed of various ratios of PTMG and PEG components by measuring the dye uptake. Experiments revealed that the higher ratio of PEG component resulted in increasing the hydrophilic property and decreasing the aggregate structure in the segmented polyurethanes. Aqueous dyeing solution, consequently, seemed to adsorb positively into the intra-molecules of polyurethanes.Considering the stress-strain relations and water-swelling characteristics of polyurethane films, the dye affinities of the films before and after dyeing were evaluated. After dyeing, the segmented polyurethane films seemed to losing hydrogen-bonding ability resulting in making the aggregate structure small. It was suggested that the dyestuff molecules were adsorbed in the hard segments of the polymers with some form of bonding.Furthermore, it was observed that the dye adsorption for CI Acid Red 114 was higher than that for CI Acid Red 37 among two kinds of acid dyes applied in this study. It was suggested as follows: (1) CI Acid Red 114 having bulky molecular structure against CI Acid Red 37, ca. 1.6 times in molecular weight, contributed to adsorb into the segmented polyurethanes with van der Waals forces. (2) CI Acid Red 114 molecule modified with formic acid in dyeing bath changing to insoluble form for water adsorbed easily onto the hydrophobic group of the segmented polyurethanes.

Polyurethane cuffed endotracheal tubes to prevent early postoperative pneumonia after cardiac surgery: A pilot study

Patients receiving mechanical ventilation through an endotracheal tube are at increased risk for pneumonia. Because microaspiration of contaminated supraglottic secretions past the endotracheal tube cuff is considered to be central in the pathogenesis of ventilator-associated and postoperative pneumonia, better sealing of the upper trachea by the endotracheal tube cuff could possibly reduce this risk. We therefore postulated that use of a polyurethane cuffed tube would prevent early postoperative pneumonia through this mechanism in a population of cardiac surgical patients. In a prospective, single-blind, randomized study, patients scheduled for cardiac surgery were allocated to intubation with a polyurethane cuffed endotracheal tube or the routinely used polyvinyl chloride cuffed endotracheal tube. Patients were scheduled for routine or emergency cardiac surgery and admitted to an 8-bed cardiac surgical intensive care unit of a tertiary care hospital. A total of 134 patients were available for analysis (67 in each group). Whereas mortality was not different between the groups, the incidence of early postoperative pneumonia and empirical prescription of antibiotic therapy were significantly lower in the polyurethane group than in the polyvinyl chloride group (23% vs 42%, P < .03). Intensive care unit and hospital stays were not significantly different between the two study subsets (3 +/- 5 days vs 3 +/- 4 days and 16 +/- 9 vs 17+/-11 days, respectively). In a multivariate regression analysis, preoperative serum creatinine levels (odds ratio 1.85, confidence interval 1.02-3.37, P = .04) and perioperative transfusion (odds ratio 1.50, confidence interval 1.08-3.37, P = .015) were independently associated with increased risk of early postoperative pneumonia, whereas use of a polyurethane endotracheal tube was protective (odds ratio 0.31, confidence interval 0.13-0.77, P = .01). Polyurethane cuffed endotracheal tubes can reduce the frequency of early postoperative pneumonia in cardiac surgical patients.

Polyurethane adhesives based on carborane-containing compounds

The results are reported of studies of adhesives based on polyurethanes containing carborane groups. It is established by TGA methods that for polyurethane-carborane systems, total mass losses upon heating to 600°C are equal to 20%, whereas for adhesives free of carborane groups, such losses are equal to 80%. It is revealed that the properties of the adhesives studied are substantially affected by carborane isomeric structure. Compositions containing polyestercarboranes with m-carborane provide higher stability of adhesive joints to elevated temperatures. Results of the study of the kinetics of gas evolution are reported and the scheme of the two-stage mechanism of thermal degradation is proposed. Results of IR spectroscopy analysis show that upon the curing of carborane-containing polyurethane composition, isocyanate groups of polyisocyanate first interact with hydroxyl groups of polyestercarborane, which results in the formation of macrodiisocyanates. Subsequent heating to 350°C leads to further curing of compositions that involves carborane, ester, and polyurethane groups.

Preparation and characterization of castor oil‐based polyurethane/poly(o‐methoxyaniline) blend film

AbstractBlends made up of castor oil‐based polyurethane (PU) and poly(o‐methoxyaniline) (POMA) were obtained in the form of films by casting and characterized by FTIR, UV‐Vis‐NIR spectroscopy, and electrical conductivity measurements. Doping was carried out by immersing the films in 1.0M HCl aqueous solution. Chemical bonds between NCO group of PU and NH group of POMA were observed by means of FTIR spectra. The UV‐Vis‐NIR spectra indicated that the presence of the PU in the blend does not affect doping and formation of the POMA phase. The electrical conductivity research was in the range of 10−3 S/cm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Hydrogen bonds in heterogeneous blends based on semicrystalline polyurethane and styrene-acrylic acid block copolymer

New film-forming polymer composites based on the semicrystalline polyurethane and the styreneacrylic acid block copolymer have been synthesized. The effect of hydrogen bonds on the phase structure and properties of the composites has been studied by dynamic MTA, DSC, thermogravimetry, and IR spectroscopy. Formation of the network of intermolecular hydrogen bonds between urethane groups of polyurethane and carboxyl groups of block copolymer components leads to a decrease in the microphase separation of the composites under study and improves their thermooxidative stability.

Effects of alleviated tension at the nerve repair site using biodegradable tubular conduits: Histological, electrophysiological and functional results in a rat model

BACKGROUND: The effect of mobilization on the functional regeneration of peripheral nerves remains controversial. Functional efficacy of alleviated tension at the nerve repair site in a full range of motion model in the rat was recently published elsewhere. This study sought to determine the effect of alleviated tension at the nerve repair site using biodegradable tubular conduits for segmental nerve splinting to block, thereby blocking variable tension. METHODS: In 60 rats, the right sciatic nerve was transected midthigh and coapted immediately microsurgically. The animals were divided into four groups. Group N, epineural nerve repair (control). For the groups listed below, segmental tubular nerve splinting with alleviated in situ tension at the nerve suture site was performed using tubular conduits of different biodegradable materials. Polyurethane group, biodegradable polyurethane tubular conduits. Neuragen group, collagen I tubular conduits. Neurolac group: DL-lactide-e-caprolactone tubular conduits. Full range of motion of lower limbs was ensured by passive motion of hind limbs once a week after functional testing. Histological and electrophysiological assessment and 12 postoperative weekly function tests (toe spread test and BBB Locomotor Rating Scale) were carried out. RESULTS: Functional results were significantly better in all groups using segmental biodegradable tubular nerve splinting for alleviated in situ tension at the nerve repair site, mainly because of less endoneural scar formation at the nerve suture segment. However, this effect was attenuated when polyurethane tubular conduits were used. Electrophysiologic results showed increased amplitude and compound nerve action potential area in the alleviated tension groups. Nerve conduction velocity was fastest in the Neuragen group. CONCLUSIONS: Complete alleviation of in situ tension at the nerve suture site with biodegradable tubular conduits seems to improve functional peripheral nerve regeneration by significant decrease of endoneural collagenization in the nerve suture segment. Additionally, our findings suggest that alleviated tension in the nerve suture segment using biodegradable conduits depends upon which material is used.

Adhesion formation and intraperitoneal catheters: Histologic findings in a rat model

Pieces of polyurethane, Teflon, silicone, and polyvinyl chloride were placed intraperitoneally to compare the histologic findings regarding intraperitoneal adhesion development in a rat model. The overall adhesion score differed significantly among the groups, the highest being in the Teflon group (mean 13.2), followed in descending order by the polyvinyl chloride group (10), the silicone group (9.6), and the polyurethane group (6.8). Thus, polyurethane causes the least adhesion development and can be used more extensively for the construction of catheters for intraperitoneal use.

Hydrogen‐bonded polyurethane complexes based on 4‐alkoxybenzoic acids as the low molar mass components

AbstractSupramolecular polyurethane complexes based on a polyurethane with a pendant pyridyl unit (PUPy) as the hydrogen bond acceptor and 4‐octyloxybenzoic acid (OOBA) or 4‐butyloxybenzoic acid (BOBA) as the hydrogen bond donor were prepared. The primary driving force for the formation of these complexes is the hydrogen bonding between the pyridyl polyurethane group and the carboxylic acid group, while the urethane group only contributes to the binding of acid molecules to a minor extent. Phase separation in the BOBA/PUPy and OOBA/PUPy systems occurred at low molar ratios: BOBA and OOBA formed amorphous polyurethane complexes at a molar ratio of 0.2, while the OOBA/PUPy complex exhibited a glassy smectic mesophase at a molar ratio of 0.4. In comparison to the previously studied complexes of PUPy and 4‐dodecyloxybenzoic acid (DOBA), where side‐chain ordering prevailed, OOBA/PUPy complexes showed a high tendency of the main‐chain crystallization at molar ratios of 0.4 or higher. This is due to weak overall van der Waals interactions between the short octyl tails and effective intra‐ and/or intermolecular hydrogen bonding between the urethane and pyridyl groups of the polymer backbone. Copyright © 2004 Society of Chemical Industry

DYNAMIC MECHANICAL STUDIES OF POLYURETHANE COMPOSITES FILLED WITH GLASS MICROFILLERS

Ceramic microspheres with unique composition and diameter, modified by different surface treatments, were blended with polyurethane (PU) in various proportions to improve the visco-elastic and mechanical properties of PU composites. Results of dynamic mechanical spectra indicate that the introduction of micro-beads H50, D32 and K37 into the PU network leads to the shift of glass transition temperature. Besides, the intensity of loss tanδ of PU composites decreased as a function of the filler's concentration, due to reduced concentration of polymer backbones. Both the shift of Tg as well as the changes of loss tanδ show that the introduction of microspheres not only creates physical bonding with PU but also causes steric effects due to the adsorption of N−H and C=O functional groups of PU on the filler surface. However, the introduction of various microfillers shows the composites to have different Young's modulus. This evidence shows that the rigidity and elasticity of polymer composite can be finely tuned by the introduction of various surface-treated microfillers as well as the amount of filler added.

Nano-structure phosphorus-containing polyurethane dispersions: synthesis and crosslinking with melamine formaldehyde resin

Nano-particle-size phosphated polyurethane dispersions were synthesised from phosphorus-containing macroglycol, bis (hydroxymethyl) propionic acid and methylene-bis-(4-isocyanatocyclohexane) (H 12MDI). After the carboxylic acid groups of the phosphated polyurethane were neutralised by suitable bases, water was added to form the phosphated polyurethane dispersion. Chain flexibility affected particle-size reduction because flexible particles are more deformable in a shear field. During phase inversion the dispersed phase can more easily be broken into smaller particles. Depending on the number of hydrophilic groups present, the dispersion can be obtained in a very finely divided form, so that it practically has the appearance of a solution. Crosslinking of the dispersions with melamine showed that hexamethoxymethyl melamine does not self-condense during the curing and co-condensation was predominant. It was further shown that the cure response of the polyurethane dispersions was affected by the nature of the neutralising amine. Triethanolamine neutralised dispersions gave very poor cure response compared with triethylamine due to the low-volatility and the tendency to enter side reaction with the melamine.

Contraceptive effectiveness of a polyurethane condom and a latex condom: A randomized controlled trial

Objective To compare the contraceptive effectivenesses of a polyurethane condom and a standard latex condom. Secondary outcomes of interest were safety, functionality, discontinuation, and acceptability. Methods We randomized 901 couples to use either the polyurethane condom or a standard latex condom as their only form of contraception. We tested for pregnancy at enrollment and at every scheduled follow-up visit (weeks 4, 10, 16, 22, and 30). Results The 6-month typical-use pregnancy probabilities were 9.0% (95% confidence interval [CI] 5.9, 12.2) for the polyurethane group and 5.4% (95% CI 2.9, 7.8) for the latex group; the hazard ratio was 1.7 (95% CI 1.1, 2.7), and we failed to reject the null hypothesis of our test of noninferiority. Females in the polyurethane group reported fewer genital irritations (hazard ratio 0.6; 95% CI 0.5, 0.8; P < .01), whereas males in both groups reported the same number of genital irritations (hazard ratio 1.0; 95% CI 0.7, 1.5; P = .94). Total clinical failures (breakage and slippage) were 8.4% for the polyurethane condom and 3.2% for the latex condom (difference 5.3%, 90% CI 2.8, 7.7). The risk of discontinuation did not differ between groups. Participants judged both condoms favorably in terms of the four primary acceptability outcomes (willingness to purchase, willingness to recommend, confidence in method, and general comfort). Conclusion The polyurethane condom was not shown to be as effective as the latex comparator condom for pregnancy prevention. However, the risk of pregnancy in the polyurethane group falls in the range of other barrier methods. For people with latex sensitivity or who find latex condoms unacceptable, this polyurethane condom represents one of several synthetic male condom alternatives currently available on the US market.