Curing the Film

Before curing at elevated temperature the coated items should be allowed to dry thoroughly at low temperature (room temperature for organic solvents or 50° -80°C for water dispersions) to remove any residual solvent. They should then be brought smoothly up to the recommended curing temperature. Any residual solvent will otherwise tend to bubble or ciss . 

Typical curing temperatures are listed in Table 11.2. In general a manufacturer s recommendations for the cure schedule should be followed, but where these are difficult because of either excessive temperature or excessive time it may be possible to reduce the temperature and increase the time or vice versa. However, for every type of binder there will be a temperature below which satisfactory curing will not take place. 

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The main disadvantage is that web temperatures of 275-325° F are required to cure the film. These temperatures affect the paper properties adversely, and therefore higher-quality, more-expensive paper must be used. Even so, blisterii or cracking in the folder may be a problem. Moreover, the solvent emission, although reduced significantly, is not eliminated, and, as with the ultraviolet light-cured inks, paper printed with these thermally-catalyzed inks cannot be recycled in the currently used processes (8, 9). 

A series of device wafers were processed along with the KBr IR plates and magnetic and IR measurements were performed using varying cure ambients. It was found that a vacuum bake at 220° C was sufficient to cure the films completely and preserve the magnetic properties of the Ni/Fe films. Figure 12 shows typical IR comparisons of the air cured and vacuum cured films. For all device applications,a vacuum bake at 220° C was chosen as the standard processing condition. 

Anhydrides. Polyanhydrides and not monoanhydrides must be used to cure epoxy surface coatings. They are used in powder form for powder coatings and in solution for can coatings both forms are hot curing. The films have a good acid resistance, and do not impart an undesirable taste to foods. 

It seems, then, that epoxidized methyl esters of oleic, linoleic, and linolenic acid contribute equally to yellowing, taking into consideration die added amount of crosslinker. The observed yellowing with epoxidized methyl ricinoleate is rather poor, and the reason for fliat is not yet fully understood. For all of the model compounds under investigation, it can be concluded that the films show poor coating characteristics after heat-curing. The films are too brittle and do not resist the standard re-versed-impact tests. It is likely fliat epoxide functionalities between 1 and 3 per alkyl chain are too low to form flexible three-dimensional networks. 

As with other techniques, the material requirements for rotogravure printing depend on the curing process. For drying (solvent removal), a viscosity of between 0.01 and 0.2 mPa s is appropriate, resulting in a film about 1 p,m thick [23], which is more than sufficient for many printed electronics applications. UV curing the film allows for thicker films, up to about 8 p,m thick. 

Residual Monomers - Compositions to be checked for unreacted monomer were prepared with 1% of hexadecane as an internal standard prior to curing. Following cure, the film was extracted with CCl for two hours in the presence of 0.5% of phenothiazine in a rolling t>ottle. Gas chromagraphic analysis is run as quickly as possible. Samples not immediately analyzed were refrigerated until used. 

Oven or autoclave used to apply heat to melt and cure the film... 

The effect of polymerization has been demonstrated with two fluorinated surfactants, one polymerizable and one nonreactive, added to polyCmethyl-methacrylate) lacquer. After curing, the films were rinsed with a solvent. Contact-angle measurements (Fig. 8.1) [47,49] showed that the film containing the polymerizable surfactant (i) had been permanently hydrophobized, whereas the nonreactive surfactant (ii) had been washed away. A preformed polymer (iii) also gave a permanently hydrophobic surface. 

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