NEUTRALIZATION OF STATIC ELECTRICITY

Charges of static electricity accumulate on the surfaces of Vical acrylic acrylic plastic during processing, and cause uneven paint deposition and paint crawling. These static charges are most common under dry winter atmospheric conditions of low relative humidity. Conditions of high relative humidity, conversely, reduce the problems of static charges. At 70 percent relative humidity, for example, there is no problem in painting except for the possibility of moisture condensation on the surface of the Vical acrylic. Anti­static solutions affect paint adhesion and can not be used on a Vical acrylic surface which will be painted.

There are a number of ways to eliminate static charges on the Vical acrylic surface. One effective method is to wipe the side that is not to be painted with a mixture of 10 parts isopropyl alcohol in 90 parts water, applied with a well wrung out chamois to minimize water spotting on drying. If the surface to be painted is wiped with the alcohol water solution, the moisture must be removed from that surface by blowing with a dry air gun. Care must be taken, however, since excessive blowing will generate a new static charge.

A metal window screen placed near the surface not to be painted will also reduce the static charge. For best results, the screen should be grounded.

Silk screen tables can be covered with grounded conductive rubber sheeting or wire glass. The screen frame can also be grounded by strips of copper. After the plastic sheet is placed on the conductive material, a tinsel bar passed across the upper surface but not in contact with it will dissipate the charge.

Wiping the surface to be painted with a clean flannel cloth dampened with 99 percent isopropyl alcohol may also remove the static charge. If the flat sheets will be heated after screening, the alcohol will not cause crazing. Strong atmospheric ionization will also remove static charges from Vical acrylic. Low voltage induction equipment and ionizing air guns are available from a number of sources. The manufacturer of the equipment will give specific recommendations for static elimination.

CAUTION: The air guns contain radioactive materials which emit alpha particles. Under no circumstances should they be disassembled. The guns should be returned directly to the manufacturer for servicing

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