Curing distilled water

Thermal analysis, moisture uptake and dynamic mechanical analysis was also accomplished on cured specimens. Thermal analysis parameters used to study cured specimens are the same as those described earlier to test resins. The moisture uptake in cured specimens was monitored by immersing dogbone shaped specimens in 71 C distilled water until no further weight gain is observed. A dynamic mechanical scan of a torsion bar of cured resin was obtained using the Rheometrics spectrometer with a temperature scan rate of 2°C/minute in nitrogen at a frequency of 1.6Hz. The following sections describe the results obtained from tests run on the two different BCB resin systems. Unless otherwise noted all tests have been run as specified above. 

Premixed blends of acrylamide and bisacrylamide prepared with varius ratios of monomers were purchased from Eastman Kodak Chemical Company (Rochester, NY). The 37.5 1 and the 19 1 preparations were used for the study. Gels made from these mixtures will be referred to as 2.6% and 5% cross-linked polyacrylamides, respectively. Five grams of each monomer blend were added to 95-g portions of distilled water. Solution was achieved by mixing for 1 h. To each sample was added 1 ml each of a 1% solution of N, N, N, N -tetramethylethylenediamine (Eastman Chemical Co., New Haven, CT) and a 10% solution of ammonium persulfate (Mallinckrodt Laboratory Chemicals, Phillipsburg, N.1). The solutions were poured into an open polyethylene mold and allowed to cure for 12 h at room temperature. The gels were carefully removed and placed in an excess of distilled sterile water for 48 h. The water was replaced several times during the equilibration period. It was felt that this was sufficient to remove unreacted monomers and impurities. The gels were then cut with a steel-ruled die into circles 40 imn in diameter. 

To determine the wet bond strength coated panels were immersed in distilled water for 1500 h, removed and discs 25.4 mm in diameter stamped from them. The surfaces were wiped with a dry tissue and bonded between two cylindrical test pieces using a polyamide cured epoxide adhesive and immediately placed in a sealed container at 100% RH for the adhesive to cure. After 16 h the specimens were broken on an Instron Universal Test Machine with minimum delay. Recovered values were measured after the panels had dried out at room temperature and humidity for 7 days. Clearly, it is unlikely that the values reported represent the minimum bond strengths, as some drying out is almost inevitable, but the values are directly comparable. 

Electrolyte 0.3% KC1 aq. solution prepared with twice-distilled water, containing 0.02 M benzotriazole. Polarization Cathodic 5 V for 10 min and 10 min without potential (with air bubbling). Joints were tested after 24 h in boiling water. Adhesive 100 parts diglycidyl ether of bisphenol A (Epon 828 from Shell Chemical Co.) cured with four parts dicyandiamide at 175DC for 2 h. 

Srogress, samples of the matrix resins were removed and cast in 1-inch iameter cylindrical aluminum cups to form discs 1/8-inch thick. These were cured in the same oven with the filament-wound structures. The discs were then placed into distilled water contained in small beakers located in a room air conditioned to maintain 25°C. Periodically, the... 

The resulting pastes, for all cases, were placed into a PVC cylindrical sleeve body. The conducting composite material glued to the copper contact was cured at 40°C during a week. Before each use, the surface of the electrode was wet with doubly distilled water and then thoroughly smoothed, first with abrasive paper and then with alumina paper (see more details on the preparation of GECE in Procedure 7). 

UMEs used in our laboratory were constructed by sealing of carbon fibre into low viscosity epoxy resin (see Fig. 32.4) [118]. This method is simple, rapid and no specialised instrumentation is required. Firstly, the fibres are cleaned with this aim. They are immersed in dilute nitric acid (10%), rinsed with distilled water, soaked in acetone, rinsed again with distilled water and dried in an oven at 70°C. A single fibre is then inserted into a 100- iL standard micropipette tip to a distance of 2 cm. A small drop of low-viscosity epoxy resin (A. R. Spurr, California) is carefully applied to the tip of the micropipette. Capillary action pulls the epoxy resin, producing an adequate sealing. The assembly is placed horizontally in a rack and cured at 70°C for 8h to ensure complete polymerization of the resin. After that, the electric contact between the carbon fibre and a metallic wire or rod is made by back-filling the pipette with mercury or conductive epoxy resin. Finally, the micropipette tip is totally filled with epoxy resin to avoid the mobility of the external connection. Then, the carbon fibre UME is ready. An optional protective sheath can be incorporated to prevent electrode damage. 

Alcohols also promote wettability and penetration of the wood surface. This may easily be shown by the following simple experiment. When equal sized drops of distilled water were placed on the surface of a freshly planed piece of southern yellow pine, the times for the drops to completely soak into the wood were observed. On the early wood it took 65 seconds and on the latewood 179 seconds. When similar drops of 50% ethanol solution were used instead of pure water, it required only six seconds to disappear into the earlywood and 26 seconds into the latewood. However, if a small drop of adhesive syrup, with no hardener added, was placed on the wood surface, no adsorption took place at all. It was surmised that the viscosity prevented its permeation. When the adhesive was diluted with 50% alcohol it was readily absorbed and produced a red stained spot on either earlywood or latewood areas. This showed that the low molecular weight adhesive molecules could readily permeate the wood structure before condensation with the curing agent. 

The effects of moisture on epoxy fracture are not conclusive. Scott et al. reported that an amine cured epoxy, normally displaying stick-slip fracture at room temperature and low rates, exhibited stable behavior when immersed in distilled water. Also, they found that the rate necessary to promote the unstable to stable crack growth transition at room temperature was increased by two orders of magnitude in the presence of the water. Yamini and Young , on the other hand, found that testing in water tended to suppress stable behavior and promote stick-slip fracture in an amine cured epoxy over a wider range... 

ASTM standard specimens and procedures were used for flexure (D-690), compression (D 695), Izod impact and torsional pendulum analysis (TPA). For tension, D1822 tensile impact specimens were substituted for D638 specimens to conserve material. Test specimens were machined from the plates and cylinders using a water cooled dlamond wheel. All the specimens were dried in vacuo at 100°C for three weeks before testing or subsequent postcure treatment. Half the specimens were post-cured for 2 hours at 225°C in vacuo before testing. Selected specimens were Immersed in distilled water at 80°C for 6 weeks for moisture uptake determinations. 

Lawson et al. (2000) examined the migration of constituents from solvent-free adhesives used to bond 12 pm PET film to 45 pm LDPE. The technique of MALDl-MS, a soft ionisation technique capable of looking at sample mixtures over a mass range of 150-500,000 Da without prior separation, was employed. The adhesives studied were based on a solution of mixed isomers of MDl in polymeric MDI with either polyether or polyester-based polyols. Pouch testing of cured laminates with distilled water was undertaken (two hours at 70 °C) with the LDPE surface in contact with the water. 

Physical properties were evaluated using standard DIN or ASTM specifications. The sealants were filled into Teflon molds to form homogeneous test pieces of comparable thickness. The specimens were then moisture cured and conditioned at 25 °C and 50% relative humidity for 14 days before mechanical property testing. The hardness of the cured sealant samples was measured by Shore A. Shelf life at 50 °C was determined for a maximum of 21 days. Tack-free times were determined by finger touch under ambient conditions. For adhesion testing the substrates were first wiped with either methyl ethyl ketone (aluminum, steel, glass, concrete, wood) or methanol (PVC, PMMA, ABS, polystyrene), then washed with detergent, rinsed with distilled water, and allowed to air dry prior to preparation of the test specimens. Specimens were cured for 14 days at ambient conditions. 

Co-immobilization Pectin, 6 g, was dissolved in 78 ml distilled water, with subsequent addition of 6 ml sodium acetate buffer (1 M, pH 4.2) and 10 g wet yeast. Silica containing immobilized enzyme (206.5 U/g dried silica or 272.2 U/g dried silica) was then mixed with the suspension at the ratio of 1.5 g of wet silica-enzyme/20 g yeast-pectin suspension. One gram of dried silica corresponded to 1.5 of wet silica. Finally, the suspension was dropped in a 0.2 M CaC solution, and 18.5 g of 4 mm spherical particles were formed after curing in a refngerator, for 18 to 20 h. 

Weighed amounts of bio-polyols, catalyst (Stannous 2-ethyl hexanoate), surfaetant (polyether-modified polysiloxane), and blowing reagent (distilled water) were mixed well in a paper cup. A prescribed amoimt of MDI was added to the mixture, which was then stirred with a high-speed stirrer (5,000 rpm) for 15 s. After stirring, the mixture was poured immediately into another paper cup, and the foam was allowed to rise and set at ambient conditions (22 °C). Finally, the foam samples were cured at room temperature for 24 h before any analysis can be conducted. The formulations of the prepared foams are shown in Table 2. 

NaCl solutions, showed typical Increases when transferred to distilled water at 212°F. Also, the fact that the Hypalon exposed to hot brine over long periods can still be seamed or patched, indicates that curing of the Hypalon does not take place. (Figure 9)... 

A RT-curing (EPl) and a hot-curing epoxy adhesive (EP2) prepared as bulk materials and as layers on two types of stainless steel have been investigated during curing and aging in dried air and in distilled water. 

Joints immersed in distilled water at 57 C for 96 hours. Cured with methylenedianiline. 

D Almeida [40] has reported interlaminar shear strength (ILSS) results for 65v/o Kevlar 49 fibres in DER 383 epoxy resin cured with 27phr DEH 50 aromatic polyamine with a void content below 0.5%. The ILSS values decreased as a function of immersion time, with specimens immersed in distilled water declining faster than those in saline solution, which is absorbed more slowly. When the results were normalized to water content the results were coincident, suggesting that the degradation mechanism was the same in both cases (Fig. 7.7). 

Davies et al. [64] studied the influence of water absorption on the interlaminar shear strength and end notch flexure (ENF mode II shear) fracture toughness of quasi-unidirectional (88% 0°, 12% 90°) E-glass fibres in DGEBA epoxy resin cured with an amine hardener. Laminates were immersed in (a) distilled water and (b) the Atlantic Ocean ( at Boca Raton, Florida) for up to 8 months at temperatures of 20°C, 50°C and 70°C. Sea water was more slowly absorbed than distilled water. This observation has frequently been made and it provides some reassurance that laboratory tests using distilled water are useful, if slightly cautious, estimates of behaviour in the ocean. 

The synthesis of arsphenamine was reported by Ehrlich and Bertheim (1912) and it was patented and then manufactured by the firm, Hoechst (DRP 224 953), and sold by them under the name Salvarsan . The initial announcement of a cure for syphilis was taken up by the newspapers, and Ehrlich became a world celebrity overnight. This fame gave him little pleasure, for he had worries that arose from the discovery. For example, arsphenamine was oxidized in the air to a more toxic product, now known to be oxophenarsine 6.4) a much more selective and desirable drug, and one that would in time replace arsphenamine (see Section 6.2). However, at that time, the uncontrolled oxidations were causing deaths, so that Ehrlich decided that arsphenamine must be issued only as single doses, and in sealed tubes from which all oxygen had been removed. He also issued directions for the preparation of solutions in sterile distilled water, neutralization, and intravenous injection without delay. These directions were often departed from, and the resulting disasters attracted unfortunate publicity. Ehrlich later introduced neoarsphenamine ( 914 ), a more soluble derivative. 

The poly(oxyphenylene) was electrodeposited from freshly prepared solution containing 0.23 M of 2-allylphenol, 0.4 M of allylamine, 0.2 M of butylcellosolve (ethyleneglycol monobutylether) in water/methanol mixture (1 1 by volume) by applying a constant potential of 4 V from constant voltage power-supply (Zentro-Elektrik, Type LA 15/156 B) between the cathode (a platinum coil of 1.5 cm area) and the substrate (anode). The current was monitored with a Keithley 177 microvoltmeter and recorded with a Metrawatt, Model SE 780 recorder. The electrodeposited films of poly(oxyphenylene) formed within half of an hour (aprox. 1.5 /xm thick) were rinsed with distilled water and cured at 150°C for 30 min. 

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