Decorating pretreatment

New pretreatments for aluminium to enable it to be nickel plated more easily have led to novel decorative applications including large mirrors. Wyszynski has described a proprietary process applicable to a wide range of aluminium alloys. 

A large segment of the metal parts produced by industry are painted for both decorative purposes as well as to increase the corrosion resistance and extend the useful life of the product. To obtain maximum quality from painted metal articles, it is of paramount importance to pretreat the metal parts with a conversion coating process. ( 1,2) Pretreatment processes contribute a significant improvement in corrosion protection and durability to metal articles by ... 

Polyethylene parts are decorated by silk screening, hot stamping, or dry offset printing. For satisfactory printing, the surface must be oxidized by hot air, flame, chlorination, sulfunc acid-dichromate solution, or electronic bombardment. Hot air or flame methods are used with molded parts flame or electronic methods with films. Inks specially made for polyethylene give best results. Roll-leaf hot stamping does not require pretreatment of the suifaoe. 

Metallized polypropylene (PP) is used today in many different fields such as automotive, decoration, electrical. In order to obtain a good adhesion between the aluminium and the polymer a pretreatment of the film prior to the metallization is necessary. Indeed, the very extreme surface of the polymer has to be modified in order to prepare it to a good adhesion with the metal. Thus the polymer is placed in a low pressure plasma of nitrogen with a corona discharge configuration of electrodes, and the metallization is carried out in situ after the pretreatment in nitrogen. This process, which simulates an industrial polymer film treatment has proven a great efficiency for very short treatment times (23 ms) (1).However, the mechanisms responsible for the improvement of adhesion are not totally explained yet. 

XANES. - Au(CH3)2(acac)/MgO X-ray absorption, near edge spectroscopy (XANES) was used to determine the oxidation state of MgO-supported Au particles. These samples were prepared by decorating the surface of MgO with a Au(III) complex Au(CH3)2(acac). The samples were then analyzed for Au oxidation state as a function of the pretreatment gas (He or H2) and pretreatment method. With increasing temperature of treatment, in either He or H2, the Au was reduced from the cation to the metal. In the absence of H2, it was speculated... 

Mcrogr q>hs show the ze and morphology evolution of the DA and AA series of catalysts (Fig. S and 6 ). The morphology changes in these catalysts with the high temperature pretreatment is evident initid spherical particles change to irregular ones decorated by small ones. Perforated particles are also observed (Fig. 7). 

Most parts are easily released from the mold after completion of the curing cycle if the mold is pretreated with waxes or silicones to lubricate the surface, and/or a mold release agent (zinc stearate, paraffin wax, etc.) is added to the resin to facilitate the removal of parts. With certain release agents, either on the mold surface or in the mix, problems such as difficulties in decorating or bonding parts after molding can occur. This is particularly true with certain silicones, which can also cause corrosion or erosion of metallic and nonmetallic surfaces when used as inserts (electrical connector, etc.). 

Priming involves the application of a coating on the surface of the plastic product to promote adhesion or to prevent attack by the solvents in a subsequent protective or decorative coating. In some cases priming can be done after cleaning. In others, it must be done after pretreatment. 

Zinc electroplated onto steel gives a bright and smooth finish. It is used for decorative effect and to protect delicate objects where rough or uneven finishes cannot be tolerated (in instrument parts) and for articles that cannot withstand the pretreatment or temperatures required in the other coating processes. Electroplated zinc is also very ductile, and the process is widely... 

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