Polyurethane paints

Compounds based on S—EB—S usually contain polypropylene, which improves solvent resistance and processibiUty and raises upper service temperatures. Compounds intended for use in the automotive industry are able to survive 1000 hours air exposure at temperatures of 125°C with only minor changes in properties (54). Very soft compounds have been developed to replace foam mbber for interior trim parts. In this and similar appHcations, these soft compounds are usually insert molded over polypropylene or metal and then coated with flexible polyurethane paint (55). Other automotive appHcations include products intended for sound deadening, flexible air ducts, and gear shifter boots, as weU as improving the properties of sheet mol ding compounds. 

Moisture-curing polyurethane paints and bituminous paints, specially formulated for the purpose, are also suited for application to damp substrates other polyurethane paints should not even be applied to dry surfaces if the relative humidity is high. 

Where fumes or deposits which act as anti-oxidants are present, no orthodox paint which dries by oxidation can give satisfactory service. Instead, a coating which dries either by evaporation (e.g. a selected chlorinated rubber paint), or by a cross-linking reaction (e.g. a catalysed epoxy or two-component polyurethane paint) must be used. 

A mathematical model has been developed describing the chemistry and the physics of the process of curing polyurethane paints. 

The curing of polyurethane paints is a complex chemical and physical process therefore a mathematical model may be a valuable tool to describe the process and manage the data. 

Both pigmented and unpigmented polyurethane paints have been prepared using a polyester resin containing hydroxyl functional groups and the biuret trlmer of hexamethylenedllsocyanate as a crosslinker. The molar ratio of hydroxyl/isocyanate has been chosen 1.0 and the pig-ment/binder ratio 0.6. 

The isocyanate concentration during curing of polyurethane paints has been quantified by tracing the infrared absorption of the isocyanate group (2272 cm- ) with a Perkin Elmer 983 spectrophotometer. 

In our opinion, the model has proved to be a valuable tool for the quantification of important phenomena occurring during the curing of polyurethane paints. 

Low melting point Low boiling point Physically soft Malleable, not brittle Low electrical conductivity Dissolve in non-polar solvents Insoluble in polar solvents Ice melts in the mouth Molecular nitrogen is a gas at room temperature We use petroleum jelly as a lubricant Butter is easily spread on a piece of bread We insulate electrical cables with plastic3 We remove grease with methylated spiritb Polyurethane paint protects the window frame from rain... 

From the data obtained for the different specimens it can be seen that there is significantly different behaviour between the poor, porous coatings (bitumen) and the polyurethane paint samples. Of the polyurethane samples only one showed any evidence of corrosion beneath the coating during the duration of the test and this was an unpigmented single coat specimen. 

Table II shows the details of preparation for the second set of 10 painted steel specimens. A polyurethane paint (Marlnox SR-2, Mabraco International, 20 des Navlgateurs, QuSbec, Canada) along with an initial coating of an aluminxim containing paint (prSpolymSre d aluminium, Mabraco International) was the second type of paint system used in this study.

Results of Impedance teste conducted on specimens with the polyurethane paint always showed capacitance In the pF cm range. In spite of no rinsing oTCrati n being carried out. The resistances are In the 10-10 0 cm range. 

Figure 7 shows the Impedance plots as a function of temperature obtained using a specimen having the polyurethane paint coating. The resistance Is of the order of 10 S2 cm and the... 

When a thick coating (-100-160 ijm) of polyurethane paint Is applied (e.g. specimen 29), the activation energy Is of the order of 26 kcal/mol. This Indicates the higher energy barrier presented by a non-porous coating. 

Figure 8 presents the Impedance behavior of polyurethane-painted specimen after 4 hours of Immersion and after 10 days of Immersion. The Impedance spectrum does not show any appreciable variation. Further Information on the behavior of the Tremclad and the Marlnox systems (specimens 25 and 27) for Immersion times upto 10 days Is given In Table IV. The variation In corrosion... 

Uses. Polyurethane paints and varnishes as an elastomer in casting compounds, flexible textile coatings... 

Uses. Production of polyurethane foams and plastics used in polyurethane paints and wire coatings the most commonly used material is a mixture of 80% 2,4 isomer and 20% 2,6 isomers... 

Two-pack polyurethane paints exhibit film properties comparable to those of solvent-borne polyurethane coatings (Bittner and Epple, 1996 Mirgel, 1993). 

Unless you have been employed in the automobile refmishing or other business where painters manually mix two-component polyurethane paint systems, it is unlikely that you will be exposed to large amounts of HDI. 

Abstract— The use of organosilanes as adhesion promoters for surface coatings, adhesives and syntactic foams is described and reviewed in the light of published work. Data are presented on the beneficial effect of silanes, when used as pretreatment primers and additives, on the bond strength of two pack epoxide and polyurethane paints applied to aluminium and mild steel. It is shown that silanes when used as additives to structural epoxide and polyurethane adhesives are less effective than when used as pretreatment primers on metals but are highly effective on glass substrates. The compressive properties of glass microballoon/epoxide syntactic foams are shown to be markedly improved by the addition of silanes. 

The effect of silanes on the bond strength of a two-pack polyurethane paint Direct pull-off, silane on surface... 

Reference to Table 7 will show the data for the two-pack polyurethane paint, and indicate a similar improvement to that of the epoxide paint due to the use of silanes. Although there are differences in the values for particular silanes on the different substrates and surface treatments, the general picture is that AAMS and MPS are the most effective in epoxide and polyurethane paints. 

Although not reported here the silanes used in conjunction with the epoxide and polyurethane paints were largely ineffective with the oxidative cure systems. 

A similar set of curves is shown in Fig. 2 for the polyurethane paint. Here again the non-silane control lost most of its bond strength in the first 3 days and the loss was continuing after 15 days. The paint containing MPS and the AAMS treated surface equilibriated after 7 days. 

Figure 2. Rate of loss of bond strength of a polyurethane paint on aluminium—under water immersion conditions.

It seems less likely that MAMS is reactive towards either epoxide or isocyanate groups. In spite of this MAMS performed well, in some cases, notably the polyurethane paint on mild steel and aluminium, see Tables 3 and 7, better than ECMS and APES. Clearly chemical reaction is not a prerequisite for bond strength enhancement. Chain tangling, simple physical effects, may play an important role with both MPS and MAMS and possibly other silanes. 

Diazocines 192 and alkyl-substituted derivatives were among lower and higher ring homologs used as catalysts for making epoxy resin hardeners and materials for elastomers, polyurethanes, paints, etc. (86JAP6133158). 

The paint used must be flexible enough to withstand all repeated movements in the material. The most suited paint is a nonyellowing polyurethane paint, which can normally be applied to the well-cleaned surface. If required, the surface can be primed with a special primer that is obtainable from the larger suppliers such as Loctite (Henkel Loctite Corporation, Dusseldorf, Germany). 

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