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PubMed2001

Characterization of thermally generated aerosols from polyurethane foam.

Isocyanates constitute a group of highly reactive chemicals used on a large scale for the production of flexible polyurethane (PUR) foam. Exposure to isocyanates is known to produce irritation of the mucous membranes and the eyes. Isocyanates also have strong sensitizing properties and may cause occupational asthma. It is therefore important to monitor isocyanate emissions at workplaces. To obtain information for the improvement of isocyanate samplers and for health risk assessments of exposure, the emitted aerosol from two types of flexible PUR foam subjected to thermal degradation was characterized. Particle size distribution and toluene diisocyanate (TDI) concentration in the emitted aerosols were measured. Thermal degradation of flexible PUR foam at temperatures from 250 to 300 degrees C produced an aerosol with a geometric mean particle diameter of 30-50 nm. Between 5% and 9% of the PUR foam was emitted as TDI, and 2% to 6% of TDI monomers were found in the particle phase under the experimental conditions used. The 2,6-TDI isomer was more abundant in the gas phase than in the particle phase.

Aerosols↗
PubMed2001

Exposure to 4,4'-methylenediphenyl diisocyanate (MDI) during moulding of rigid polyurethane foam: determination of airborne MDI and urinary 4,4'-methylenedianiline (MDA).

Occupational exposure to 4,4'-methylenediphenyl diisocyanate (MDI) was measured during moulding of rigid polyurethane foam. The aim of the study was to find out whether an MDI-derived urinary amine metabolite could be detected in the urine of workers exposed to apparently low levels of MDI. Airborne MDI was sampled on 1-(2-methoxyphenyl)-piperazine (2MP)-impregnated glass fibre filters and determined by high-performance liquid chromatography (HPLC) using ultraviolet (UV) and electrochemical (EC) detection. The limit of detection of MDI was 3 ng ml-1 for a 20 microliters injection. The precision of sample preparation, expressed as relative standard deviation (RSD), was 1.3% with UV detection and 2.1% with EC detection at a concentration of 70 ng MDI ml-1 (n = 6). The 2MP-MDI derivative was stable at +4 degrees C up to eight weeks. The accuracy of the method was validated in an international quality control programme. Workers (n = 57) from three different factories participated in the study. Urinary 4,4'-methylenedianiline (MDA) metabolite was determined after acid hydrolysis as heptafluorobutyric anhydride derivatives by gas chromatography-mass spectrometry using chemical ionisation and monitoring negative ions. The limit of detection in urine was 0.2 nmol l-1. The precision of six analyses for a urine sample spiked to a concentration of 1 nmol l-1 was 29% (RSD). The MDI concentrations were below the limit of detection in most (64%) of the air samples collected in the worker's breathing zone. Still, detectable amounts of MDA were found in 97% of the urine samples. Monitoring of urinary MDA appears to be an appropriate method of assessing MDI exposure in work environments with low or undetectable MDI concentrations in the workplace air.

Adult↗
PubMed2002

Determination of isocyanates, aminoisocyanates and amines in air formed during the thermal degradation of polyurethane.

An air sampling method for the determination of isocyanates, aminoisocyanates and amines formed during the thermal degradation of polyurethane (PUR) is presented. The method is based on the collection of air samples using impinger flasks containing di-n-butylamine (DBA) in toluene with a glass fibre filter in series. Isocyanates are derivatized with DBA to urea derivatives, and amines are derivatized in a subsequent work-up procedure with ethyl chloroformate (ET) to carbamate esters. Amine, aminoisocyanate and isocyanate derivatives were characterized using liquid chromatography-time of flight mass spectrometry (LC-TOFMS) and liquid chromatography-chemiluminescent nitrogen detection (LC-CLND). Quantification was performed by LC-MS, monitoring molecular ions [MH]+ in the electrospray mode. The instrumental detection limits for amines, aminoisocyanates and isocyanates were in the ranges 30-40, 2-3 and 3-70 fmol, respectively. Thermal degradation products of PUR were observed in high concentrations during welding in district heating pipes and PUR-coated metal sheets. Eleven isocyanates, three amines and five aminoisocyanates were identified. The concentrations of isocyanates, aminoisocyanates and amines in samples collected in the smoke close to the welding spot were in the ranges 150-650, 4-290 and 1-70 ppb, respectively. In samples collected in the breathing zone, isocyanates and aminoisocyanates were observed in the ranges 9-120 and 4-19 ppb, respectively. The compounds were present in both gas and particle phases. Volatile compounds dominated in the gas phase, whereas less volatile compounds dominated in the particle phase. The method presented makes it possible to sample and determine amines and aminoisocyanates, in addition to isocyanates. The need to monitor these compounds is clearly illustrated by the high concentrations found during the thermal degradation of PUR.

Air Pollutants↗
PubMed2002

On-line solid phase extraction with polyurethane foam: trace level spectrophotometric determination of iron in natural waters and biological materials.

This paper reports the development of a simple and accurate on-line procedure for preconcentration and determination of dissolved iron in waters and biological materials using unloaded polyether-type polyurethane foam as solid extractor. In the developed flow injection system, the analyte was preconcentrated from acidic aqueous medium as iron-thiocyanate complex with post-elution with ascorbic acid solution and spectrophotometric measurement with 1,10-phenanthroline as colorimetric reagent. In order to improve the performance of the system several chemical and flow variables were investigated as well as the effect caused by the presence of possible interferents. The method was validated by the analysis of two certified reference materials. Application of the methodology was carried out by the determination of dissolved iron content in eight natural water samples with different characteristics. The results were compared with those obtained by electrothermal atomic absorption spectrometry (ETAAS) and no statistical difference was observed. The detection limit was 0.75 microgram l-1 and the RSD was 1.2% for 2 min preconcentration time. At this condition, a productivity of 20 samples h-1 was achieved. Increasing the preconcentration time up to 3 min, a detection limit of 0.45 microgram l-1, an RSD of 1.5% and an analytical throughput of 15 h-1 were verified.

Automation↗
PubMed2002

Exposure to airborne isocyanates and other thermal degradation products at polyurethane-processing workplaces.

The thermal degradation products of polyurethanes (PURs) and exposure to isocyanates were studied by stationary and personal measurements in five different occupational environments. Isocyanates were collected on glass fibre filters impregnated with 1-(2-methoxyphenyl)piperazine (2MP) and in impingers containing n-dibutylamine (DBA) in toluene. connected to a glass fibre postfilter. The derivatives formed were analysed by liquid chromatography: 2MP derivatives with UV and electrochemical detection and DBA derivatives with mass spectrometric detection. The release of aldehydes and other volatile organic compounds into the air was also studied. In a comparison of the two sampling methods, the 2MP method yielded about 20% lower concentrations for 4,4'-methylenediphenyl diisocyanate (MDI) than did the DBA method. In car repair shops, the median concentration of diisocyanates (given as NCO groups) in the breathing zone was 1.1 microg NCO m(-3) during grinding and 0.3 microg NCO m(-3) during welding, with highest concentrations of 1.7 and 16 pg NCO m(-3), respectively. High concentrations of MDI, up to 25 and 19 microg NCO m(-3), respectively, were also measured in the breathing zone during welding of district heating pipes and turning of a PUR-coated metal cylinder. During installation of PUR-coated floor covering, small amounts of aliphatic diisocyanates were detected in the air. A small-molecular monoisocyanate, methyl isocyanate, and isocyanic acid were detected only during welding and turning operations. The diisocyanate concentrations were in general higher near the emission source than in the workers' breathing zone. A sampling strategy to evaluate the risk of exposure to isocyanates is presented.

Air Pollution, Indoor↗
PubMed2002

Biological monitoring of aromatic diisocyanates in workers exposed to thermal degradation products of polyurethanes.

Exposure to diisocyanates was assessed by biological monitoring among workers exposed to the thermal degradation products of polyurethanes (PURs) in five PUR-processing environments. The processes included grinding and welding in car repair shops, milling and turning of PUR-coated metal cylinders, injection moulding of thermoplastic PUR, welding and cutting of PUR-insulated district heating pipes during installation and joint welding, and heat-flexing of PUR floor covering. Isocyanate-derived amines in acid-hydrolysed urine samples were analysed as perfluoroacylated derivatives by gas chromatography mass spectrometry in negative chemical ionisation mode. The limits of quantification (LOQs) for the aromatic diamines 2,4- and 2,6-toluenediamine (2,4- and 2,6-TDA) and 4,4'-methylenedianiline (4,4'-MDA) were 0.25 nmol l(-1), 0.25 nmol l(-1) and 0.15 nmol l(-1), respectively. The LOQ for the aliphatic diamines hexamethylenediamine (HDA), isophoronediamine (IpDA) and 4,4'-diaminodicyclohexyl methane (4,4'-DDHM) was 5 nmol l(-1). TDA and MDA were detected in urine samples from workers in car repair shops and MDA in samples from workers welding district heating pipes. The 2,4-TDA isomer accounted for about 80% of the total TDA detected. No 2.6-TDA was found in the urine of non-exposed workers. The highest measured urinary TDA and MDA concentrations were 0.79 nmol mmol(-1) creatinine and 3.1 nmol mmol(-1) creatinine, respectively. The concentrations found among non-exposed workers were 0.08 nmol mmol(-1) creatinine for TDA and 0.05 nmol mmol(-1) creatinine for MDA (arithmetic means). Exposure to diisocyanates originating from the thermal degradation of PURs are often intermittent and of short duration. Nevertheless, exposure to aromatic diisocyanates can be identified by monitoring diisocyanate-derived amines in acid-hydrolysed urine samples.

Adult↗
PubMed2004

Determination of technical grade isocyanates used in the production of polyurethane plastics.

A method for determination of technical grade isocyanates used in the production of polyurethane (PUR) is presented. The isocyanates in technical grade products were characterised as di-n-butylamine (DBA) derivatives using LC-MS and LC-chemiluminescent nitrogen detection (CLND) and the total isocyanate content was compared to a titration assay. For collection of isocyanates in air, an impinger-filter sampling technique with DBA as derivatisation reagent was used. Characterised DBA and nonadeuterium labelled DBA derivatives of isocyanates in technical products were used as calibration standards and internal standards, respectively, in the analysis of air samples. Three workplaces were studied where PUR products were produced either by spraying or by moulding. In both technical products and in air samples, a number of monomeric, oligomeric and prepolymeric isocyanates of e.g. methylenebisphenyl diisocyanate (MDI) and hexamethylene diisocyanate (HDI) were characterised. Several of these have not previously been described in workplace atmospheres. In the technical isocyanate products, between 69 and 102% of the NCO content determined by titration was accounted for by LC-CLND. Quantifications of a wide range of isocyanates in air samples were performed with correlation coefficients in the range 0.988-0.999 (n= 8) and the instrumental detection limits were 0.7-25 pg. At the two workplaces where MDI- and HDI isocyanurate-based products were sprayed, the isocyanate composition in the air reflected the composition in the technical product. At the workplace where a MDI-based product was used in a moulding process, only the monomeric isocyanates were found in the air. The advantage of using characterised technical grade isocyanates as analytical standards was clearly demonstrated and the possibility of using index compounds when monitoring isocyanate exposure is discussed.

Air Pollution, Indoor↗
PubMed2003

Fungi are the predominant micro-organisms responsible for degradation of soil-buried polyester polyurethane over a range of soil water holding capacities.

AIMS: To investigate the relationship between soil water holding capacity (WHC) and biodegradation of polyester polyurethane (PU) and to quantify and identify the predominant degrading micro-organisms in the biofilms on plastic buried in soil. METHODS AND RESULTS: High numbers of both fungi and bacteria were recovered from biofilms on soil-buried dumb-bell-shaped pieces of polyester PU after 44 days at 15-100% WHC. The tensile strength of the polyester PU was reduced by up to 60% over 20-80% soil WHC, but no reduction occurred at 15, 90 or 100% soil WHC. A PU agar clearance assay indicated that fungi, but not bacteria were, the major degrading organisms in the biofilms on polyester PU and 10-30% of all the isolated fungi were able to degrade polyester PU in this assay. A 5.8S rDNA sequencing identified 13 strains of fungi representing the three major colony morphology types responsible for PU degradation. Sequence homology matches identified these strains as Nectria gliocladioides (five strains), Penicillium ochrochloron (one strain) and Geomyces pannorum (seven strains). Geomyces pannorum was the predominant organism in the biofilms comprising 22-100% of the viable polyester PU degrading fungi. CONCLUSIONS: Polyester PU degradation was optimum under a wide range of soil WHC and the predominant degrading organisms were fungi. SIGNIFICANCE AND IMPACT OF THE STUDY: By identifying the predominant degrading fungi in soil and studying the optimum WHC conditions for degradation of PU it allows us to better understand how plastics are broken down in the environment such as in landfill sites.

Biodegradation, Environmental↗
PubMed2002

Light microscopy evaluation of polyurethane vascular grafts porosity by Sudan Black B staining.

In small-diameter vascular grafts, the porosity of the internal surface plays an important role because it affects initial thrombus deposition and therefore the graft's patency. As well as many other studies reported in the literature we have carried out a study of the relationship between porosity and the manufacturing parameters of polyurethane (PU) grafts by standard scanning electron microscopy (SEM) analysis. However, SEM was not completely satisfactory for evaluating the 'sponge-like' uptake of water by the graft due to the unavoidable water loss and metal coating during preparation. In fact this preparation produces artefacts of the three-dimensional porous structure. To avoid this problem we investigated the possibility of observing the graft's internal surface through a stereomicroscope after it had absorbed water. We looked into a simple staining procedure which preferentially colours the PU graft fibres with respect to the void areas. After testing different kinds of stains, we eventually found that Sudan Black B, which usually stains for all kinds of lipid, turned out to be an excellent stain for the water-loaded PU grafts when diluted with ethanol. This staining procedure, coupled with a computerized image analysis system, allowed us to evaluate the degree of void and average void size of the graft internal surface and to correlate these data with graft density and manufacturing parameters.

Azo Compounds↗
PubMed2000

Selection of a polyurethane membrane for the manufacture of ventricles for a totally implantable artificial heart: blood compatibility and biocompatibility studies.

Membranes made from 4 commercial poly(carbonate urethanes): Carbothane (CB), Chronoflex (CF), Corethane 80A (CT80), and Corethane 55D (CT55), and from 2 poly(ether urethanes): Tecoflex (TF) and Tecothane (TT) were prepared by solution casting and sterilized by either ethylene oxide (EO) or gamma radiation. Their biocompatibility was evaluated in vitro in terms of proliferation, cell viability, and adhesion characteristics of human umbilical veins (HUVEC), monocytes (THP-1), and skin fibroblasts, and by measuring complement activation through the generation of the C3a complex. Their hemocompatibility was determined by measuring the level of radiolabeled platelet, neutrophil, and fibrin adhesion in an ex vivo arteriovenous circuit study in piglets as well as via an in vitro hemolysis test. The results of this study showed no endothelial cell proliferation on any of the materials. The cell viability study revealed that the CB, CF, and TF membranes sterilized by EO maintained the highest percentage of monocyte viability after 72 h of incubation (>70%) while none of the gamma-sterilized membranes displayed any cell viability. The fibroblast adhesion and C3a generation assays revealed that none of the materials supported any cell adhesion or activated complement, regardless of the sterilization method. The hemolysis test also confirmed that the 4 poly(carbonate urethanes) were hemolytic while none of the poly(ether urethanes) were. Finally, the ex vivo study revealed that significantly more platelets adhered to the CB and CT55 membranes while the levels of neutrophil and fibrin deposition were observed to be similar for all 6 materials. In conclusion, the study identified the CF and TF membranes as having superior biocompatibility and hemocompatibility compared to the other polyurethanes.

Animals↗
PubMed2001

Growth of endothelial cells on different concentrations of Gly-Arg-Gly-Asp photochemically grafted in polyethylene glycol modified polyurethane.

To improve endothelial cell adhesion and growth on the surface of polyethylene glycol modified polyurethane (PU-PEG), cell adhesive peptide Gly-Arg-Gly-Asp (GRGD) was photochemically grafted to the surface. The surface grafted GRGD-N-Succinimidyl-6-[4'-azido-2'-nitrophenylamino]hexanoate (SANPAH) on a PU-PEG surface was performed by adsorption and subsequent ultraviolet irradiation. Fourier transform infrared spectra (FTIR) and electron spectroscopy for chemical analysis (ESCA) confirmed the GRGD grafted to form a PU-PEG-GRGD surface. The composition fraction of nitrogen calculated from ESCA analysis for the PU-PEG-GRGD surface was well correlated with the concentration of GRGD to be immobilized. Human umbilical vein endothelial cells (ECs) were well adhered and growing on the PU-PEG-GRGD surface. Moreover, the viability of ECs growing on PU-PEG-GRGD surfaces, analyzed by MTT test, was also well correlated with the GRGD concentrations immobilized on the surface. With photochemical techniques, we could manipulate different contents of GRGD to form multiple regions of PU-PEG-GRGD surface that could enhance the growth of ECs on the surface, and the enhancement efficiency was well correlated with GRGD contents.

Cell Adhesion↗
PubMed2003

A polyurethane vascular access graft and a hybrid polytetrafluoroethylene graft as an arteriovenous fistula for hemodialysis: comparison with an expanded polytetrafluoroethylene graft.

AIM: We evaluated a polyurethane vascular access graft (TVAG), a hybrid polytetrafluoroethylene graft (hPTFEG), and an expanded polytetrafluoroethylene graft (ePTFEG) for postoperative complications and graft patency in their use as prosthetic devices of vascular access for hemodialysis. METHODS: Between August 1993 and October 2001, we treated 200 patients in whom A-V fistulas were placed by the same surgeon. These were divided into the following four groups according to the type of blood access: 27 cases of ePTFEG, 23 cases of TVAG, 22 cases of hPTFEG, and 128 cases of an autogenous A-V fistula. We calculated the cumulative patency rates by the Kaplan-Meier method, including primary (problem-free) and secondary (revised or functional) patency rates. RESULTS: The hPTFEG group experienced few thromboses. The absence of perigraft edema in the TVAG group permitted the early use of the TVAG within a few postoperative days for hemodialysis. Among the three graft groups, the primary patency was the best in the hPTFEG group (94.7% at 1 year and 86.1% at 2 years), with a significant difference versus the ePTFEG group. In regard to secondary patency, hPTFEG had an excellent patency of 100% at 1 year and 90.9% at 2 years, and TVAG had a comparable patency with that of ePTFEG. CONCLUSION: The hPTFEG was considered superior to ePTFEG in terms of being complication-free and had the excellent 2 year secondary patency of 90.9%. TVAG, with a patency equal to that of ePTFEG, could be used immediately after implantation due to the absence of limb edema.

Arteriovenous Shunt, Surgical↗
PubMed2000

Lumbar catheterization of the subarachnoid space with a 32-gauge polyurethane catheter in the rat.

Chronic catheterization of the subarachnoid space of rats is an important tool for intrathecal drug delivery in pharmacologic investigations of pain. We describe a technique using direct lumbar insertion of a small 32-gauge polyurethane (PU) catheter without extensive surgery. Location of the catheter was confirmed with 2% lidocaine injection 1 day later, and methylene blue injection after 7-14 days. This method improved recovery of the rat after catheter implantation and reduced neurologic complications.

Animals↗
PubMed2006

Seeding of human vascular cells onto small diameter polyurethane vascular grafts.

INTRODUCTION: Thrombogenicity of small diameter vascular prostheses might be reduced by complete coverage of the luminal surface with vascular cells. We investigated cell seeding on polyurethane vascular prostheses (PUVP). METHODS: 45 PUVP were divided into three groups of n = 15 each: Group A (diameter 20 mm, gamma-sterilized), Group B (diameter 4 mm, gamma-sterilized), and Group C (diameter 4 mm, ethylene oxid [Eto]-sterilized). Human smooth muscle cells (SMC), fibroblasts (FB), and endothelial cells (EC) were isolated from saphenous vein segments and expanded in culture. PUVPs were pre-seeded with a mixed culture of FBs and SMCs (mean 7.7 +/- 2.3 x 10(6) cells) followed by EC seeding (mean 4.4 +/- 0.9 x 10(6) cells). Seven days after cell seeding, PUVPs were perfused under a pulsatile flow. Flow definitions were as follows: adaption phase: low flow, resulting pressure: 60/30 mm Hg; high flow: resulting pressure: 160/50 mm Hg, lasting for 4 hours in all groups. Three subgroups were defined out of each group, differing in the perfusion strategy: high flow immediately, adaption phase of 15 minutes followed by high flow, and adaption phase of 30 minutes followed by high flow. Specimens were taken after each seeding procedure, prior to and after perfusion, and then examined using a scanning electron microscope (SEM) and immunohistochemical staining procedures. RESULTS: Pre-seeding with the mixed culture revealed a better initial adhesion in Groups A and B compared to group C (76% vs. 41%). In Groups A and B, EC seeding (adhesion 72%) resulted in a confluent EC layer. Immunohistochemical stainings were positive for collagen IV, laminin, CD31, and factor VIII, but negative for eNOS. In Group C, only isolated cells were found after each seeding procedure, which rounded up and vanished during the next days. When perfused with high-flow immediately, Group A and B prostheses revealed small defects (< 10% of the surface) of all cell layers. After perfusion with an adaption phase of 15 minutes only few defects were found within the EC layer with an intact basement membrane. An adaption phase of 30 minutes resulted in a confluent cell layer without significant cell defects. After perfusion, the endothelial cells also stained positive for eNOS. CONCLUSION: Seeding of a mixed culture consisting of FBs and SMC resulted in an excellent EC adhesion and resistance to shear stress. Cell attachment was better on gamma-sterilized PUVPs compared to Eto-sterilization. The cells obviously maintained their ability to adapt to shear stress.

Adaptation, Physiological↗
PubMed1988

Patency rate of small caliber fibrous polyurethane vascular prostheses implanted in the dog carotid and femoral artery improved by use of acetylsalicylic acid and dipyridamol.

Segments of 3 mm diameter fibrous polyurethane vascular prosthesis of length 3-4 cm were prepared. They were bilaterally implanted in the carotid and femoral arteries of male and female beagles. Four groups consisting of animals receiving either no medication or thrombocyte aggregation drugs were studied: Group A (8 dogs), no medication: group B (19 dogs), 500 mg acetylsalicylic acid (ASA) once daily and 25 mg dipyridamol (DIP) three times daily orally for 6 weeks after the implantation operation; group C (14 dogs), 250 mg ASA and 25 mg DIP three times daily orally for 6 weeks after the implantation operation; group D (12 dogs), 250 mg ASA and 25 mg DIP three times daily orally for 25 weeks after the implantation operation. Medication was started one week prior to the implantation operation. In group A, all prostheses were occluded at week 6. There was a significant difference in patency rates between groups B-D and C-D. No significant differences in patency rates could be found between groups B and C. The best patency rates were obtained 25 weeks after implantation in group D for both the right and left carotid and right and left femoral implantation sites. Highest patency rates were observed when ASA and DIP were given for 25 weeks.

Animals↗