Open cures

Rubber) open cure, -lager, n, bonded warehouse, -lagerprtifung, /. Paints, etc.) exposure test(ing). freilassen, t.t. set free, liberate. 

Concrete structures should be constructed in accordance with BS 5337 or BS 8110 as appropriate. The concrete must be properly cured under shuttering, or a curing membrane, for seven days followed by at least 28 days open curing prior to the commencement of lining. Surfaces have to be free from voids and projections and are often screeded to give a satisfactory finish. 

The calendering process and its conditions are developed or modified according to the requirements of subsequent operations and the purpose for which the sheet is used. Thus for sheets which are to be open cured, such as in chemical plant lining and custom built items such as inflatables and ebonite pipes, roll coverings for paper and steel mills, the calendering needs to be more exact than the sheets which are used for blank preparation for molding of... 

The screw in the injection unit is not compressed and is charaeterised by its relatively low L/D ratio of 15 1 (compare this to 20 1 for thermoplastics). This is brought about by having the feed zone shifted forward. A surface-cured serew is used as standard. A fully eured version is advised for use with extremely abrasive materials. Bimetal construction of the eylinder makes for extremely long service life. Generally, the heating eontrol systems can be adjusted aeross three or four independent temperature zones. An open, cured nozzle is serewed directly into the nozzle soeket and can therefore be tempered precisely. 

Application Open/cure time Shelf life Storage Wt. Gal. 

Furan hot-box resins are used in both ferrous and nonferrous foundries (66,67). In this process, resin and catalyst are intimately mixed with dry sand and then blown into heated metal boxes containing a cavity the shape of the desired core. In seconds, the surface of the sand mass hardens and, as soon as the core has cured sufficiently to be rigid and handleable the box is opened and the core removed. Automotive cores with exceUent dimensional accuracy and high strengths are made via this forty-year-old process. 

Both the hquid and cured 2-cyanoacryhc esters support combustion. These adhesives should not be used near sparks, heat, or open flame, or ia areas of acute fire ha2ard. Highly exothermic polymerization can occur from direct addition of catalytic substances such as water, alcohols, and bases such as amines, ammonia, or caustics, or from contamination with any of the available surface activator solutions. 

With a sufficiently long press cycle, a state of complete cure is reached. At this point, the laminate is cooled in the press, under pressure, and removed for finishing operations. If the press is opened at a temperature above the boiling point of trapped volatiles, vaporization occurs causing interlaminar blistering which mins the laminate. 

Foam. PhenoHc resin foam is a cured system composed of open and closed ceUs with an overall density of 16—800 g/cm. Principal appHcations are in the areas of insulation and sponge-like floral foam. The resins are aqueous resoles cataly2ed by NaOH at a formaldehyde phenol ratio of ca 2 1. Free phenol and formaldehyde content should be low, although urea may be used as a formaldehyde scavenger. 

Catalyst Selection. The low resin viscosity and ambient temperature cure systems developed from peroxides have faciUtated the expansion of polyester resins on a commercial scale, using relatively simple fabrication techniques in open molds at ambient temperatures. The dominant catalyst systems used for ambient fabrication processes are based on metal (redox) promoters used in combination with hydroperoxides and peroxides commonly found in commercial MEKP and related perketones (13). Promoters such as styrene-soluble cobalt octoate undergo controlled reduction—oxidation (redox) reactions with MEKP that generate peroxy free radicals to initiate a controlled cross-linking reaction. 

Those that cure well between these temperatures are often referred to as intermediate set. Cold set types naturally set much faster at intermediate temperatures. Cold pressing of plywood is usually done in a hydraulic press. The press may then be opened, the clamped assembly removed and allowed to stay under the pressure of the clamps for at least four hours to set the glue. 

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). 

To make a decorated plate, the mold is opened shortly after the main charge of molding compound has been pressed iato shape, the decorative foil is laid ia the mold on top of the partially cured plate, ptinted side down, and the mold closed again to complete the curing process. The melamiae-treated foil is thus fused to the molded plate and, as with the decorative lamiaate, the overlay becomes transparent so that the ptinted design shows through yet is protected by the film of cured resia. 

Fig. 9. Initiation of epoxy cure. Irradiation of a triaryl sulfonium salt produces a radical cation that reacts with an organic substrate RH to produce a cation capable of releasing a proton. The proton initiates ring-opening polymerization. X = BF , PFg, AsFg, and SgFg. ...

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