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PubMed2005

Dynamic infrared linear dichroism study of the temperature-dependent, viscoelastic behavior of a poly(ester urethane).

In the study reported here, of the poly(ester urethane), Estane 5703, simultaneous dynamic mechanical analysis (DMA) and dynamic infrared linear dichroism (DIRLD) measurements have been carried out at continuously variable temperatures from -50 to +30 degrees C. Multivariate curve resolution-alternating least squares (MCR-ALS) analysis of the spectral data has been correlated with the thermo-mechanical properties. Spectral changes, analyzed as a function of temperature, are compared with the storage and loss moduli to provide insight into viscoelastic behavior at the molecular level. In addition, the data for pure Estane have been compared to those for plasticized Estane samples, which contain 10 and 30% plasticizer by weight. These comparisons show a strong and consistent correlation between the macroscopic rheological properties and the microscopic (molecular, inter-molecular, and sub-molecular) responses of this block co-polymer.

Circular Dichroism↗
PubMed2005

Midterm results with the use of polycarbonate urethane heterografts for dialysis access.

Dialysis access surgery is currently one of the most common vascular operations as the dialysis patient population increases. Although autogenous arteriovenous fistulae stand as the preferred method of access due to excellent patency and lower complication rates, grafts may provide alternative approaches when an autogenous fistula is impractical usually due to depleted veins. We aimed in this study to assess early and midterm outcome with the use of Expedial heterografts (LeMaitre Vascular Ltd., Wrexham, UK) for angioaccess between October 2000 and December 2004. Patients were prospectively followed for pre- and peri-operative course with 1st, 6th and 12th month outpatient controls for patency and complication rates. A total of 34 heterografts were implanted in 30 patients (22 males and 8 females; median age 60.6 years, range 32 - 70). The mean followup for 30 patients were 16.3 +/- 6.1 (range 4 - 30) months. 28 grafts (82.4%) were placed in forearm position. Primary and secondary patencies were found as 81% and 94%, respectively (p = 0.15), with the median censored primary and secondary patencies of 27 +/- 1.7 months (95% CI, 23.38 to 30.67) and 30.42 +/- 1.1 months (95% CI, 28.30 to 32.54), respectively. Only presence of diabetes was found as a significant risk factor in the regression model (p = 0.01). We suggest that the polycarbonate urethane heterografts with acceptable patency/complication rates and shorter maturation times for dialysis access serve an alternative for these patients.

Adult↗
PubMed1991

Polyether urethane urea membrane for an improved hemodialysis.

This paper reviews our current activities of developing polyether urethane urea membranes for hemodialysis application. It is observed that the processing parameters such as precipitation medium, precipitation temperature etc. can influence the porosity of the membrane and subsequently the permeability property. Polyurethane/poly(methyl methacrylate) blended membranes have also shown high permeability. All the membranes are subjected to different sterilization processes and the pore sizes before and after sterilization are determined. The changes in the pore size due to sterilization seems to effect the permeability.

Biocompatible Materials↗
PubMed2006

Development of composite porous scaffolds based on collagen and biodegradable poly(ester urethane)urea.

Our objective in this work was to develop a flexible, biodegradable scaffold for cell transplantation that would incorporate a synthetic component for strength and flexibility and type I collagen for enzymatic lability and cytocompatibility. A biodegradable poly(ester urethane)urea was synthesized from poly(caprolactone), 1,4-diisocyanatobutane, and putrescine. Using a thermally induced phase separation process, porous scaffolds were created from a mixture containing this polyurethane and 0%, 10%, 20%, or 30% type I collagen. The resulting scaffolds were found to have open, interconnected pores (from 7 to >100 um) and porosities from 58% to 86% depending on the polyurethane/collagen ratio. The scaffolds were also flexible with breaking strains of 82-443% and tensile strengths of 0.97-4.11 MPa depending on preparation conditions. Scaffold degradation was significantly increased when collagenase was introduced into an incubating buffer in a manner that was dependent on the mass fraction of collagen present in the scaffold. Mass losses could be varied from 15% to 59% over 8 weeks. When culturing umbilical artery smooth muscle cells on these scaffolds higher cell numbers were observed over a 4-week culture period in scaffolds containing collagen. In summary, a strong and flexible scaffold system has been developed that can degrade by both hydrolysis and collagenase degradation pathways, as well as support cell growth. This scaffold possesses properties that would make it attractive for future use in soft tissue applications where such mechanical and biological features would be advantageous.

Animals↗
PubMed2004

Light-curing reinforcement for denture base resin using a glass fiber cloth pre-impregnated with various urethane oligomers.

The purpose of this study was to investigate the flexural properties of denture base resin reinforced using glass fiber cloth and a urethane oligomer. The five types of oligomer used in this study were S5, S9, S3, U4, and U6, which have varying functional groups and viscosities. The flexural properties of S9 with glass fiber cloth could not be measured because S9 is elastic. In the heat-cured resin reinforced with S9, the reinforcement peeled away from the resin. In the self- and light-cured resins reinforced with S9, the flexural properties increased significantly. When reinforced with the other four oligomers (S5, S3, U4, and U6), the flexural strength and flexural modulus of the self-, heat-, and light-cured resins increased significantly (p<0.01).

Acrylic Resins↗
PubMed2005

Mechanical properties of an experimental soft lining material based on urethane oligomer.

The purpose of this study was to investigate the apparent viscosities and mechanical properties of two experimental light-curing soft lining materials (SLM-1 and SLM-2) based on soft-type urethane oligomers, as well as the shear bond strength and dye penetration between the denture base resin and the polymerized SLMs after storage in water. The apparent viscosities of SLM-1 and SLM-2 were 144.0-146.9 and 1.9 Pa x s respectively. After storage in water for two prescribed periods (one day and three months), the mechanical properties of the SLMs on the overall were 10.6-20.6 MPa for elastic modulus, 69.3-72.1 for hardness, and 3.8-4.0 MPa for adhesive strength. Tensile strength was observed to decrease after three months' storage in water, when compared to that after one-day storage (p < 0.01). Water sorption rates also differed significantly (p < 0.05)--namely 3.0 and 2.8 mg/cm2 for SLM-1 after one day and three months respectively, and 2.0 and 2.2 mg/cm2 for SLM-2. As for dye penetration, no infiltration was observed at the denture base resin-SLM interface after three months' storage. Based on the results of this study, it seemed like the SLMs possess many suitable properties for use with a new technique that we recently developed for preparing denture base resin and soft lining material.

Acrylic Resins↗
PubMed2002

[Quantitative characterization of adsorbed bovine serum albumin on modified surfaces of poly(ether urethane) materials using ATR-FT-IR spectroscopy].

Attenuated total reflection (ATR) FT-IR spectroscopy was used to quantitatively characterize the extent of bovine serum albumin (BSA) adsorbed on the surface-coating-modified poly(ether urethane) (PEU) matrix. The two surface modifying additives (SMA) were respectively a tri-block-coupling-polymer of stearyl poly (ethylene oxide)-4,4'-methylene diphenyl diisocyanate-stearyl poly(ethylene oxide), for short MSPEO, and another similar block-coupling polymer with the Cibacron Blue F3G-A endgroups, for short cibaMPEO. The experiments of static BSA adsorption were composed by two parts. One was static isothermal adsorption, and the other was static adsorption kinetics. The quantitative characterization was based on the optical principles of FT-IR, method of experiment and index of the apparatus, by which the enhancement of BSA adsorption on the SMA-modified surfaces was confirmed.

Adsorption↗
PubMed1991

The mechanical and microscopic aspects of the deformation and fracture of a poly (ether urethane-urea) spun arterial prosthesis.

The mechanical properties of a microporous, electrostatically spun poly (ether urethane-urea), used in the construction of arterial prostheses, have been examined, with particular reference to anisotropic, crack initiation processes and preconditioning. The results demonstrate considerable anisotropy in relation to samples derived from circumferential and longitudinal directions of the tube wall structure related to the spinning process. There is also a considerable difference in crack initiation on inner and outer surface of the arterial wall, again related to the processing conditions. The results provide an important contribution to an understanding of structure-property relationships in microporous arterial prosthesis.

Biocompatible Materials↗
PubMed1992

A new technique for the custom fabrication of mouthguards with photopolymerized urethane diacrylate.

The use of protective mouthguards in athletes has proven to be an effective and inexpensive means of preventing traumatic injuries to the teeth and supporting structures. Of the three general types of mouthguards available currently, the custom-fabricated type is considered superior to stock and mouth-formed protectors. A new technique is introduced for the fabrication of custom-made mouthguards with light-curing urethane diacrylate material.

Acrylic Resins↗
PubMed1998

[Study on the structures of poly (urea) urethane by FTIR and 1H NMR methods].

Using the FTIR and 1H NMR methods, the structures, relative ratio and inventory ratio of segmented poly (urea) urethanes which are synthesized with different extenders (1,4-butandiol, ethylene diamine and their mixtures)have been studied successfully and the ratationship between the branch ratio and inventory ratio has been determined.

English Abstract↗
PubMed2006

[FTIR spectroscopic studies of hydration effect on the molecular structure of polyether urethane].

The interaction between water molecules and the polar groups in linear polyether urethane was studied by FTIR and subtraction spectroscopy technique. Direct proofs of the combining of water molecule and carbonyl group were obtained. The reorganizations of the ether linkage, carbamate, and carbon-hydrogen chain after hydration were also observed. These results suggest that the FTIR and subtraction spectroscopy technique could be a useful tool to investigate the hydration mechanism of polymer materials.

English Abstract↗
PubMed1990

[Mechanical properties and curing depth of urethane tetramethacrylate-based composite resins].

Mechanical properties and curing depth of light-cured composite resins based on five types of urethane tetramethacrylate (UTeMA; IP-4 M, XY-4 M, MC-4 M, HM-4 M and TM-4 M) were investigated, and compared them with those of UDMA-based composite resins. Composites based on UTeMA monomers containing an aromatic or cyclohexane ring in their chemical structure (IP-4 M, XY-4 M and MC-4 M) showed a relatively rigid properties than those based on aliphatic UTeMA (HM-4 M and TM-4 M). The composite resins based on XY-4 M monomer showed a curing depth and transmission coefficient superior to the other composite resins. UTeMA-based composites showed a significantly higher rigid properties than UDMA-based composites, while their rigidity did not improve the flexural strength.

Composite Resins↗
PubMed1989

[Adhesive efficiency of new bonding agents to dentin on bonding agent using urethane acrylate oligomer].

The tensile bond strength of new bonding agents on human dentin treated with 37% phosphoric acid solution for 60 sec to a photocurable composite resin was measured and the fractured surface was then observed by SEM. The new bonding agents consisted of various 20 wt% high molecular monomers (MW. 1500, 5000, urethane acrylate oligomer) as a base monomer. The best bonding agent was a mixture of 20 wt% 1500 molecular monomer as a base monomer and the value of the tensile bond strength was 91 +/- 17 kgf/cm2. The tensile bond test and SEM image of the fracture surface suggested that a high molecular monomer as a base monomer promoted the adhesive efficiency to human dentin.

Acrylic Resins↗
PubMedDate not supplied

Polyether-urethane elastomers for small-diameter arterial prostheses.

Textile polymers have been used for the manufacture of synthetic arterial prostheses. The extreme rigidity of these polymers has severely limited the nature of the structures that could be fabricated, so that the mechanical properties and structural form of the prostheses bear little resemblance to those of natural arteries. The variety of chemical structures, of mechanical properties and of means of fabrication make it possible to produce a compliant flexible prosthesis having a more delicate structure, thereby acquiring better tissue and blood compatibility and good long-term durability. These, and an acceptable form that encourages good surgical practice, account for the good performance of the prosthesis. By way of illustration, an electrostatically spun microfibrous arterial prosthesis of small diameter is described. It is made of a polyether-urethane urea (Biomer). We report good two-year patency for arterial prostheses of our design used to replace the common carotid artery in dogs.

Animals↗
PubMed1980

Blood pressure and heart rate response to apomorphine in urethane anesthetized rats.

The mechanisms involved in the hypotensive effect of apomorphine were studied in urethane anesthetized rats. The intravenous injection of apomorphine (0.01-0.75 mg/kg) produced a dose dependent fall in mean blood pressure. At the higher doses used (0.5-0.75 mg/kg) a marked bradycardia accompanied the hypotensive effect. These cardiovascular effects were prevented by pretreating the animals with pimozide (0.01-0.1 mg/kg). Low doses of haloperidol (0.03-0.3 mg/kg) did not antagonize the hypotensive action of apomorphine. Higher doses of haloperidol (1-3 mg/kg) reduced markedly the mean blood pressure. Atropine (1 mg/kg) partially antagonized the decrease in mean blood pressure induced by apomorphine and prevented completely the bradycardia. Hexamethonium (10 mg/kg) reduced the mean blood pressure and when apomorphine was administered, a residual hypotensive effect and no bradycardia was observed. It is concluded that the cardiovascular actions of apomorphine are central in origin and mainly due to the stimulation of a dopamine receptor. A probable peripheral effect could not be discarded.

Animals↗
PubMed1998

New 1,2,3-triazole derivatives (ureas, amides, urethanes) with a potential biological interest.

This paper reports the preparation of three series of 1,2,3-triazole derivatives bearing an ureido substituent (compounds 5a-h), a carboxamido substituent (compounds 6a-f) or an urethane substituent (compounds 7a-l). Some compounds were submitted to in vitro functional tests on guinea-pig isolated intestinal preparations and/or to in vitro antitumor and antiviral screening. The tested compounds showed no activity on guinea-pig ileum, except compound 7g, provided of contracturant properties; similarly, no anticancer or antiviral significant activity was found.

Animals↗