Curing problems

With this system there is no serious curing problem for coatings under 50 mils thick, but for coatings of the order of 100 mils, about three weeks are required to remove the volatile solvents... 

Cure problems can be divided into problems that give material defects and problems that make the process inefficient. Some examples of common problems of the first type will be discussed in this section. 

This message is discouraging, because it implies that unintended consequences can never be avoided. As the more acute problems affecting humans and their environment are tackled and cured, problems that had seemed inconsequential can suddenly become limiting. Nevertheless, the experienced biological engineer should be more able than others to anticipate the likely consequences of his or her technological fixes and to be prepared to deal with than. 

It is indispensable to thoroughly stir up pourable RTV-2 silicone rubber bases and components, with the exception of the transparent or translucent grades, prior to use in order to redisperse homogeneously any inactive filler that might have settled during storage. Otherwise severe curing problems may result. 

The bipartite beams bonded with the adhesive layers 009 and 013 did not perform as expected. The adhesive layers yielded at very low loads when the first beams were tested (Fig. 33). A visual inspection indicated curing problems the adhesive layer had not fully hardened. Later tests in the laboratory of the adhesive manufacturer confirmed problems with scaling up whereas the samples produced in the labora-... 

Combat risks at source, rather than taking palliative measures - cure problems not alleviate. 

Newer types of high-performance paints used on ship exteriors include those based on epoxy resins, polyurethane resins, vinyl resins (also vinyl/ alkyd or vinyl/acrylic blends) or chlorinated rubber. Epoxies and polyurethanes are chemically-curing types and present curing problems at low temperatures, whilst the overcoating intervals are critical for best adhesion... 

A major sub-group, the modified phenolics , was developed to reduce brittleness, still a very pronounced family characteristic. This modified, more flexible form, is widely and effectively used in the aircraft construction industry. However, the family as a whole has not proved to be particularly attractive in mass production engineering industries where the curing problems are not easily accommodated. Despite this, their role as laminating and bonding agents in the traditional wood-associated industries and the capability of the modified form to bond metal are important. 

Pigmentation of UV coatings has always presented curing problems. Thioxanthones were shown to have utility in these applications. This photoinitiator class absorbs in longer wave length regions of the UV spectrum where pigment absorptions are less intense. 

Don t make unrealistic promises, e.g. about curing problems or staying until better . Always check your consultant s and CMHT s views, especially regarding timescales. Involve a few key staff (e.g. CC, ward manager), and reinforce the community plan wherever possible ... 

The DIIS convergence accelerator is available for all the SCF semiempirical methods. This accelerator may be helpful in curing convergence problems. It often reduces the number of iteration cycles required to reach convergence. However, it may be slower because it requires time to form a linear combination of the Fock matrices during the SCF calculation. The performance of the DIIS accelerator depends, in part, on the power of your computer. 

Alternative Methods of Curing. The presence of salt in hides and skins has been a problem for taimers. Moreover, the quantity of salt, usually 10—20% by weight in cured hides, is an environmental problem. In the discharge of the water from the rewet and washing, the soluble soHds are normally greater than 20, 000 mg/L. This amounted to 2000 4000 mg/L in the combined waste stream of the taimery. 

Textiles. Microwave drying of textiles is under investigation, in addition to the possible uses for curing of impregnated and dyed fabrics (182). A microwave clothes dryer for consumer or commercial apphcation is also under discussion (183). Considerable developmental work and media pubhcity have occurred. Problems remain, however, particularly relating to arcing and resonant heating of metal objects that may be present in a load of clothes. These problems may be alleviated by operation at 915 rather than 2450 MHz (184). 

Spectroscopy. Infrared spectroscopy (48) permits stmctural definition, eg, it resolves the 2,2 - from the 2,4 -methylene units in novolak resins. However, the broad bands and severely overlapping peaks present problems. For uncured resins, nmr rather than ir spectroscopy has become the technique of choice for microstmctural information. However, Fourier transform infrared (ftir) gives useful information on curing phenoHcs (49). Nevertheless, ir spectroscopy continues to be used as one of the detectors in the analysis of phenoHcs by gpc. 

The recovery of fiber from broke (off-specification paper or trim produced in the paper mill) is compHcated by high levels of urea—formaldehyde and melamine—formaldehyde wet-strength resin. The urea resins present a lesser problem than the melamine resins because they cure slower and are not as resistant to hydrolysis. Broke from either resin treatment may be reclaimed by hot acidic repulping. Even the melamine resin is hydrolyzed rapidly under acidic conditions at high temperature. The cellulose is far more resistant and is not harmed if the acid is neutralized as soon as repulping is complete. 

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