Curing condition

The processing of hides and skins into leather results in a large quantity of waste materials (9). The hide in the salt-cured condition contains salt in a crystalline form, water as salt solution, and as hide Hquid components, flesh, blood, manure, and surface dirt from the animal. 

The maximum recommended film thickness is 25 p.m. At greater thicknesses, volatiles from the curing reaction, mainly water and some formaldehyde and phenol, can cause defects. These coatings have excellent electrical insulation properties, ie, up to 20 V/p.m, because of low moisture absorption and low conductance. The coatings are hard with low flexibiUty, depending on curing conditions and film thickness. 

Laminates are pressed in steam-heated, multiple-opening presses. Each opening may contain a book of as many as ten laminates pressed against pohshed steel plates. Curing conditions are 20—30 min at about 150°C under a pressure of about 6900 kPa (1000 psi). 

Erequendy, the curing equipment available, ie, presses, autoclaves, LCM lines, etc, do not allow the curing conditions to be varied as desired, so the compounder must design a cure system compatible with the existing equipment while also meeting the compound performance requirements. 

Although sealant manufacturer s Hterature commonly reports modulus values, these values must be interpreted carefully. Specimen sizes, test rate, cure conditions, and the time a sealant has been allowed to cure when tested can all have a significant effect on modulus. Therefore, for a tme comparison, sealants should be evaluated by a standard test that examines all sealants by the same procedure. In general, the longer a sealant has been allowed to cure, the more reaUstic the modulus data. 

The compression set of sihcone mbber is similar to organic types of mbber at low (0—50°C) temperatures, ranging from 5 to 15% (380). Above 50°C, sihcone mbber is superior, but compression set increases with time and temperature. Sihcone mbber is more tear-sensitive than butyl mbber, and the degree of sensitivity is a function of filler size and dispersion, cross-link density, and curing conditions. The electrical properties of sihcone mbber are generally superior to organic mbbers and are retained over a temperature range from —50 to 250°C (51). Typical electrical values for a heat-cured sihcone mbber are shown in Table 9. 

Typical substrates for siUcone release coatings are supercalendered kraft paper, glassines, and thermally sensitive films such as polyethylene and polypropylene. Ideal curing conditions are 150°C or lower, and line speeds are as fast as 460 m /min. Key properties for release coatings are cure speed, integrity of cure, and stable release values. 

Resin-based repeUents may be used alone or in combination with durable-press resins. They are widely used as extenders for fluorochemical repeUents. When used alone, several of the resin-based finishes require an acid catalyst and curing at temperatures above 150°C for maximum repeUency and durabUity. When coappUed with durable-press finishes, which themselves require a magnesium chloride catalyst, the catalyst and curing conditions for the durable-press finish provide the necessary conditions for the repeUent. 

Post-Curing. Post-curing at elevated temperatures develops maximum physical properties (tensile strength and compression-set resistance) in fluorocarbon elastomers. General post-cure conditions are 16 to 24 h at 200 to 260°C. 

The ASTM heat distortion temperature (deflection temperature under load) test may be used to characterise a resin. Resins must, however, be compared using identical hardeners and curing conditions. 

Since the functionality available for curing most commercial PF resins is likely to consist mainly of o-hydroxymethyl units, it is obvious that these groups do condense al signihcant rates under the high temperature curing conditions that... 

Polymerization and curing rates of novolacs depend strongly on the acidity of the reaction mixture. Fig. 16 depicts the general pH dependence. Fig. 17 shows a partial structure for a hexa-cured novolac. Incorporation of amine is widely, though not universally, reported in hexa-cured novolac structures. In addition to the structure shown in Fig. 17, A, A -dibenzyl and A, A, A -tribenzylamine linkages have been reported [185-192]. The main by-products of hexa-curing conditions are water and ammonia, though formaldehyde is also produced. The structure and abundance of the amino portions of the cured polymer vary considerably with conditions. 

One-step vulcanization, wide range of curing conditions, high loading elasticity, snappiness, no deformation, weatherability. ozone resistance, heat resistance, tear resistance, coating performance, adhesive properties, skid resistance, abrasion resistance... 

Epoxy phenolic coatings These materials are also cured at relatively high temperatures and are made by the reaction of the epoxy resin with the phenolic resin. They are slightly less critical in application requirements, are less sensitive to curing conditions and can be applied in thicker coats. The best use for both these materials is as tank linings used for the storage or food products, drinks, etc. or for process plant, evaporators, etc. that contain boiling water. 

Gel time values of the three systems measured as abrupt change in the slope of G (t) under isothermal curing conditions show that gelation occurs earlier in PWE system at all temperatures considered as shown in Table 11.27. ETPI behaves like a catalyst for the primary epoxy-amino reaction which dominates the cure until vitrihcation occurs. Dynamic mechanical analysis and dielectric spectroscopic analysis carried out by the authors also confirm the above conclusions. 

Thermocouples were placed in the curing part so that the model could be compared to the actual process. The model accurately predicted the cure time and temperature curing profiles for several parts with different geometries and curing conditions. 

Urea-formaldehyde resins are used as the main adhesive in the forest product industry because they have a number of advantages, including low cost, ease of use under a wide variety of curing conditions, low cure temperatures, water solubility, resistance to microorganisms and to abrasion, hardness, excellent thermal properties, and a lack of color, especially in the cured resin. 

Modification of the FT-IR analysis techniques to analyze coatings under isothermal cure conditions provides the data needed to determine the rate constants for each reaction. An effective method to generate the rate constants from the experimental data has been found and will be described. 

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