Spray application, polyurethanes

Spray applications of rigid polyurethane - Alternatives currently in use for spray applications include carbon dioxide/water and HCFC-14 lb. Long-term alternatives will be HFCs. 

Pipe fittings such as bends, tees and crosses, unless large enough to enable spray application of the lining, are usually lined by casting using internal mould formers. The pipe fitting is assembled with the internal mould and preheated, the polyurethane mixture injected and the whole is oven cured. 

Large institutional and commercial refrigerators, freezers, and cold storage areas, including cryogenic equipment and gas tanks, are insulated with polystyrene or polyurethane foams. Polystyrene foam is popular where cost and moisture resistance are important polyurethane is used for spray application. Polystyrene foam is also used in load-bearing sandwich panels for low-temperature applications. 

ASTM C 945-81 (1987) Standard Practice for Design Considerations and Spray Application of a Rigid Cellular Polyurethane Insulation System on Outdoor Service Vessels, 11 pp (Comm C-16)... 

Inhalation and dermal exposure can occur during the manufacture and use of HDI. Workers and individuals in close proximity to an area where spray applications of polyurethane paints may be exposed. 

These two-pack cold-cure solvent-borne coatings have excellent durability and abrasion resistance. They are designed for spray applications on steel, aluminium and light alloy surfaces wMch have been suitably pretreated. Base and hardener are mixed in 3 1 or 5 1 ratios as recommended by the manufacturer and the pot life is around 2 hours under normal working conditions (20 C) and should not be used after the stated time. Polyurethane/acrylic resin combination is also available. Two-pack polyurethanes are widely used in veMcle body repair and can contain isocyanate which is a basic constituent in the production of polyurethane and is the most common cause of industrial asthma and it is also a skin irritant. It should be easily identified by a label on the container which should say contains isocyanates, harmful by inhalation and in contact with skin . Waterborne two-pack polyurethane finishes are available. 

In essence these systems carry out a job similar to that performed for very many years in the polyester chop-and-spray applications, the only differences being that polyurethane has a different profile of reactivity and viscosity build-up than polyester and that, at least in one case, the glass roving is conducted through the mixing device instead of being fed outside of it. 

Due to its advanced technology and low cost the rubber industry often prefers the use of sulphur-vulcanized polyurethane elastomers even though some of their technical properties, e.g. resistance to thermal degradation, are inferior to the peroxide- and diisocyanate-cured grades which often have short processing times (i.e. they are scorchy) and whose cure may be adversely affected by the presence of moisture in the unvulcanized rubber mix water is present in rubber fillers, e.g. carbon blacks usually contain about 0-5-1% and some non-black fillers such as silicas and clays 2-10%. Also to maximize scorch time it is common practice to quench-cool the rubber after internal mixing by immersion in cold-water tanks or by cold-water spray application to the surface of the hot-milled sheet. 

Spra5ung of the foam formulation by special two-stream spray gims onto suitable surfaces is often conducted. On-site applications for spray foam include roofs, tanks, vessels, cavity walls, and pipes. Spray-applied polyurethane foams are produced in densities ranging from 1.3 to 3.0 Ib/ft (21-48 kg/m ). The lower-density foams are used primarily in nonload-bearing applications (cavity walls and residential stud-wall insulation). The higher-density foams are used in roofing applications. The 1 1 volume ratio of the A and B components required for spray foams excludes the poly(isocyanurate) chemistry from this application. In spray foam formulations, PMDI in combination with the more reactive amine polyols... 

Applications. The principal use for rigid polyurethane foams is for iasulation ia various forms utilized by a variety of iadustries. Lamiaates for resideatial sheatiag (1.2 to 2.5 cm thick with aluminum skins) and roofing board (2.5 to 10.0 cm thick with roofing paper skins) are the leading products with about 45 metric tons of Hquid spray systems also ia use. Metal doors iasulated by a pour-ia-place process coastitute another substantial use. 

A typical application of these coatings is the use on carrier pipes installed by thrust boring techniques at major road, rail and river crossings. Sprayed polyurethane coatings of 900 thickness, are also commercially available on ductile iron pipes. 

Although rolling and dipping are sometimes used, power spray painting is the usual method of paint application. Among the coatings used are polyurethane, epoxy, acrylic, alkyd and vinyl based paints. With paints that are oven cured, products must have sufficient heat resistance to survive without distortion, etc. 

Application verification (AV) monitors are devices that are placed within test plots to measure actual spray deposition that occurred during application. The main function of AV monitors is to show whether or not the intended amount of test material was actually deposited on the soil surface. Application monitors consisting of soil-filled containers, paper disks, polyurethane foam plugs, and glass Petri dishes have all been used successfully for this purpose. Prior to using a monitor in the field, it is important to determine that the test substance can indeed be successfully extracted from the monitor and that the compound will be stable on the monitor under field conditions... 

Table 9.2 summarizes some technological characteristics of typical one-pack and two-pack FBZ formulations, as well as the curing conditions. Viscosity is sufficiently tow and suitable for spray or roll applications. In most cases, high-solid coatings can be obtained. The materials described herein include the bicomponent polyurethanes obtained by addition of Z1030 to Z1072 or Z1073... 

The bulk of the ngid polyurethane and polyisocyanurate foam is used in insulation. See also Insulation (Thermal) More than half (60%) of the rigid foam consumed in 1994 was in the form of board or laminate die remainder was used in pour-in-place and spray foam applications. 

All conventional spray foams are based on polyurethane (PU) systems [1]. They provide excellent mechanical properties and outstanding thermal insulation. Thus, they are widely used especially in construction, i.e. pipe or building insulation and interior applications. 

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