This equipment, frequently referred to as hot spray”, is prevalent not only in two component coating systems like polyurea coatings and polyurethane coatings, but also in polyurethane spray foams.
Dynamic tensile strength of polyurea is measured at an ultrahigh strain rate of 1.67 × 107 s−1 by generating spall failures inside thick polyurea coatings bonded to steel plates using laser-generated stress waves of several nanoseconds in duration. Polyureas were first developed in the early 1980's for automotive fascia applications due to their high strength and impact resistance. Polyurea coatings are of interest for coating because they are tougher than urethanes and can be applied to metal surfaces by spray techniques with good adhesion.
Polyurea coatings as spray foam applications has been a proven technique for extending the durability and life of many substrates. Traditionally, a polyurea protective coating is applied using a high-pressure spray system, removing the excessive overspray typically associated with high-pressure applications. Moreover, these exhibit superior characteristics in spray applications such as improved mechanical, thermal, and chemical resistance, short curing and setting time and high durability as compared to its substitutes.
Figure 7: After the test, pictures of the back faces of steel plates with polyurea sprayed on the back surface: (a) 2 mm polyurea coating; (b) 4 mm polyurea coating; (c) fragments of 4 mm coating. The polyurea coatings disconnected from the steel plate surface and showed a circular debonded area at the center of the plates. As shown in Table 6 , in both cases of 2 mm and 4 mm coating thickness, the steel plates with polyurea coated on the front surface performed better than those covered on the rear face at blast tests.
The thick (4 mm) and thin (2 mm) polyurea coatings, whether on the front or back surface of steel plates, reduced about 40% and 30% of the deflection deformation, respectively, while the areal density increased by only 27% or 13%. It should be noted that, due to spray inhomogeneity, the thickness of the polyurea coating was not as precise as the thickness of steel plates. The research was focused on the questions how the location of polyurea coating with respect to the loading direction and the thickness of polyurea coating affect the blast resistance performance of steel plates.
Influencing factors should be taken into account 12 - 15 Ackland et al. 12 applied commercially produced coatings on the surface of mild steel plates to carry out close-in blast experimental tests in air. Roland et al. 8 , 9 applied elastomeric coatings on the front face to enhance the ballistic resistance of steel armor under impact loading generated by a high-speed projectile. Polyurea is particularly suited for coating concrete in construction applications, such as roof repairs, car park decks and bridges, where the spraying environment often varies from day to day.
Polyurethane and polyurea coatings are ideal for protecting concrete against the effects of moisture, abrasion, corrosion, and chemical attack. Polyurethane and polyurea coatings protect concrete against the effects of moisture, abrasion, corrosion, and chemical attack.
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