Requirements for curing

The use of nylon-11 for powder coatings or dry coatings (qv) has been developed in response to a growing concern for the environment (44) (see Coating PROCESSES, powder technology). Electrostatic deposition allows thin films to be appHed to metal substrates. Once the powder is appHed, it must be melted and coalesced into a continuous plastic film. Eorced draft or irradiant ovens are used for fusion, and because no polymerization or cross-linkage are required for curing, coated objects can be processed quickly and air-cooled (45). 

A number of modified amines have been marketed commercially. For example, reaction of the amine with a mono- or polyfunctional glycidyl material will give a larger molecule so that larger quantities are required for curing, thus helping to reduce errors in metering the hardener. 

Due to the absence of the non-rubber constituents present in the NR some differences in compounding occur, although, in essence, the principles are the same. An increased level of stearic acid is generally required for cure activation and approximately 10% extra accelerator is necessary to achieve a similar cure rate to NR similar sulphur levels are, however, used. IR can be cured by the same type of systems as NR. 

Large-mass parts Conventional coating of large-mass parts requires exceedingly long times in convection ovens. A considerable reduction of times required for cure is to melt the powder with IR and use fast UV-initiated free radical curing reactions. 

Lossick JG, Muller M, Gorrell (1986) In vitro drug susceptibility and doses of metronidazole required for cure in cases of refractory vaginal trichomoniasis. J Infect Dis 153 948-955... 

The fact that a 10-minute press time at 150 °C and 150 psi was required before high wet strength was obtained indicated the need for more energy to cure the lignin adhesive than was required for cure of a phenolic adhesive. The... 

Apply only thin adhesive layers, since the moisture on the surface required for curing is insufficient for a complete cure (particularly at low atmospheric moisture). 

HOST FACTORS A critical determinant of antibiotic efficacy is the status of the host humoral and cellular defense mechanisms. In the immunocompetent host, merely halting the multiplication of the microorganism with a bacteriostatic agent frequently is sufficient to cure the infection. If host defenses are impaired, bacteriostatic activity may be inadequate and a bactericidal agent is required for cure. Examples where this applies include bacterial endocarditis, bacterial meningitis, and disseminated bacterial infections in nentropenic patients. Patients with HIV-1 infection and acquired immunodeficiency syndrome have impaired cellular immune responses. Therapy for opportunistic infection therefore often is snppressive bnt not cnrative disseminated infections with Salmonella or atypical mycobacteria typically require prolonged antibiotic therapy to prevent relapse. 

A cure rate study (as detailed previously) was carried out to assess UV cure response of the dlepoxyslloxane model compounds, and to compare them with cure response of analogous dlepoxy organic results. The UV flux required for cure of 2 mil coatings of these materials using both lodonium catalysts is displayed in Table V. 

An advantage of such modified amines is that because of higher molecular weight larger quantities are required for curing, and this helps to reduce errors in metering the hardener. These hardeners are also extremely active, and the pot life for a 500-g batch may be as little as 10 min. 

The thickness of an oil-paint coating is restricted on account of the atmospheric oxygen required for curing. With thick layers (25-30 pm on vertical surfaces and... 

The amine is just a catalyst and is not consumed in the reaction. After curing, it remains in the sand of the mould or core and has to be purged. The purging period currently lasts 10 to 15 times longer than the injection of the amine. The amount of amine required for curing is about 0.05 % based on the sand weight, but typically 0.10 to 0.15 % is used. 

A study of microwave curing (70) effectiveness was made with a magnetron at 28 W power and a frequency of 2.45 Ghz in an 18 cm diameter cylindrical tunable cavity. With this system, samples can be cured in 10 min to approximately 99% conversion as measured by DSC. By way of comparison, for thermal samples, heating at 195 °C for two hours and postcure at 240 °C for one hour was required for cure to this extent. 

Each of the above concepts, as well as other factors such as energy requirements for cure and post-cure effects, are major contributors toward developing radiation curable coating systems that have bonding capabilities to a wide variety of substrate materials. The major emphasis of this paper will center on polymer design for improved adhesion. 

Except for some epoxy compounds, heat and pressure are usually required for curing. Most alloy adhesives are solvent-based dispersions or 100% solids. These adhesives have a balanced combination of properties and are generally stronger over wider temperamre ranges than other adhesives. They are suitable as structural adhesives and are used where the highest and strictest end-use conditions must be met (regardless of cost) such as in military applications. ... 

Lewis Acids. Lewis acids, eg, boron trihalides, contain an empty outer orbital and therefore seek reaction with areas of high electron density. Boron trifluoride, BF3, a corrosive gas, reacts easily with epoxy resins, causing gelation within a few minutes. Complexation of boron trihalides with amines enhances the curing action. Reasonable pot lives using these complexes can be achieved because elevated temperatures are required for cure. Reactivity is controlled by the choices of the halide and the amine. The amine choice also affects other properties such as solubility in resin and moisture-sensitivity. Boron trifluoride monoethylamine (BF3 NH2C2H5), a crystalline material which is a commonly used catalyst, cures epoxy resins at 80-100°C. A chloride version is also commercially available. Other Lewis acids used in epoxy curing include stannic chloride and tin octanate. 

The definition of 5afe-Drive-Away Time (SDAT) is the time required for curing of the windshield adhesive to achieve full passenger retention in the case of a defined crash (Fig. 69). 

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