PAINTABILITY

Wood Preservation. The use of chromium compounds ia wood preservation is largely because of the excellent results achieved by chromated copper arsenate (CCA), available ia three modifications under a variety of trade names. The treated wood (qv) is free from bleeding, has an attractive ohve-green color, and is paintable. CCA is widely used, especially ia treating utility poles, bull ding lumber, and wood foundations. About 62% of all the chromic acid produced ia the United States is consumed by the wood preservation industry (77,167) (see Building materials, survey). 

A long-standing goal in polyolefins is the synthesis of polymers bearing polar functional groups such as acrylate, esters, or vinyl ethers, etc [24,40]. These copolymers might endow polyolefins with useful properties such as adhesiveness, dyeability, paintability, and print-ibility. Advances have recently been made in polymerizing polar monomers with cationic metallocene catalysts... 

Other alloy additions in commercial use include iron (often a two-layer electroplated coating with less iron—typically 20% —in the under-layer to assist formability and more iron—often 80% —in the outer layer to assist paintability) cobalt (0.15-0.35%) similar amounts of chromium (the zinc/ chromium/chromium-oxide coating known as Zincrox) and a range of ternary alloys and of composite coatings. 

The need to paint the blends has also resulted in new painting systems. Recently, a nonpolar color coat based on a hydrogenated polybutadiene diol and melamine resin for TPO bumper fascia was invented. The breakthrough technology allows the elimination of the TPO pretreatment step such as adhesion promoter, flame, or plasma during manufacturing. The paintability of two different types of E-plastomers was evaluated. The olefinic white paint was found to provide excellent paint adhesion for both types of metallocene plastomers. Paint peeling was not observed in any of the test... 

Catalyzed paints, while quite expensive, do have superior coverage as well as excellent protective qualities. They can be used not only on walls but on work benches, equipment, or any other paintable surface. 

Table 5. Improved paintability of Polystyrene Plate Treated by Surface Photografting Method.

PPO/PA blend for passenger cars. A new conductive version of the on-line paintable Triax PA/ABS blend is proposed by Bayer. Heat deflection temperature is in the 180-200°C range ensuring resistance to the temperatures encountered in the drying ovens during cathodic dip coating. 

For example, the scratch resistance of talc-filled TPOs modified with 2-3% silicone from masterbatches is significantly improved and visible whitening is suppressed under conditions that damage the same TPO without silicone. Paintability must be verified but a low silicone level (2.5% for example) does not affect paintability, and weathering resistance increases showing less change in aspect than the control without silicone. 

PPE/PA alloys are more heat-resistant allowing in-line paintability. Surface appearance reaches Class A for automotive parts. 

They must be mounted flush with the ceiling or the walls (or partitions) and sealed with paintable silicone. 

WOOD PRESERVATIVE. A material applied to wood to prevent its destruction by fungi, wood-boring insects, marine borers and fire. A common characteristic of these materials is toxicity to those organisms that attack wood, or in the case of fire retardants the ability to control combustion in terms defined by the Underwriters Laboratory. In addition, a satisfactory wood preservative must aiso (a) be capable of penetrating wood, (bi remain in the wood for extended periods withonl losing its effectiveness due to chemical breakdown, (c) be harmless to humans and animals, (d) be noncorrosive and. (e) be available in quantity at a reasonable cost, Foi certain uses, the preservative may be required to be colorless, odorless, nonswellmg and paintable. 

Paintability is generally not a problem under dry normal conditions. Unusually high relative humidity conditions can affect adhesion of the paint film or cause chemical crystal blooming on the paint surface due to the increased moisture content of the wood. Natural or clear finishes are generally not used for treated wood because the chemicals may cause darkening or irregular staining. 

Polymer manufacturers offer paintable grades of polypropylene or copolymer blends with talcum or other mineral fillers with such grades the tolerance of over-treatment seems to be increased—which can be advantageous, especially with flame treatment. 

In the manufacture of highly resilient flexible foams and thermoset RIM elastomers, graft or polymer polyols are used. Graft polyols are dispersions of free-radical-polymerized mixtures of acrylonitrile and styrene partially grafted to a polyol. Polymer polyols are available from BASF, Dow, and Union Carbide. In situ polyaddition reaction of isocyanates with amines in a polyol substrate produces PHD (polyhamstoff dispersion) polyols, which are marketed by Bayer (21). In addition, blending of polyether polyols with diethanolamine, followed by reaction with TDI, also affords a urethane/urea dispersion. The polymer or PHD-type polyols increase the load bearing properties and stiffness of flexible foams. Interreactive dispersion polyols are also used in RIM applications where elastomers of high modulus, low thermal coefficient of expansion, and improved paintability are needed. 

Several techniques including corona discharge [1], plasma treatment [1,3,4], flame treatment [1], and irradiation with UV light in the presence of a UV sensitive gas [5-8] have been developed to modify the polymer surface. The principle of those surface treatment technologies is to introduce polar groups onto the polymer surface. This provides significant improvement of wettability, paintability, biocompatibility and also adhesion to other polymers or metals. 

A number of phenols, especially chlorinated phenols and certain metal-organic compounds, such as copper naphthenate and phenyl mercury oleate, are effective preservatives. Pentachlorophenol and copper naphthenate are most commonly used, and are carried into the wood in 1-5 percent solutions in petroleum oil. Pentachlorophenol is colorless, and can be applied in clear volatile mineral oils to mill-work and window sash requiring a clean, nonswelling, and paintable treatment. 

It is evident in Figures 30.18 and 30.19 that, after the accelerated adhesion test, the primer-coated air LPCAT treated TPOs showed poor adhesion performance as compared to argon and methane LPCAT-treated TPOs. This is a clear indication that air-plasma treatment can achieve the paintable surface but cannot provide the treated surface that can be painted in a durable manner. The poor durability can be attributed to (1) the water-sensitive nature of adhesion and (2) the excessive degradation of polypropylene that causes weaker boundary layer. 

Beneficial properties One-component system good adhesion without the use of primer paintable good resistance to ultraviolet radiation easy application and clean-up good packing stability low cost fast skinning... 

The reaction conditions must be mild enough that the reacted wood still possesses the desirable properties of wood. The wood should remain strong, retain its natural color (unless a color change is desirable), still be a good electrical insulator, not become dangerous to handle, and be gluable and paintable. 

Most of the chemicals used in fire-retardant formulations have a long history of use for this purpose, and most formulations are based on empirical investigations for best overall performance. These chemicals include the phosphates, some nitrogen compounds, some borates, silicates, and more recently, amino-resins. These compounds reduce the flame spread of wood but have diverse effects on strength, hygroscopicity, durability, machinability, toxicity, gluability, and paintability (J, 12, 13). 

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