The bonding of plastic sheeting to metal is a recent development of the surface coating industry. The product, a pre-finished material, has the strength of the base metal and exterior finish of the plastic. It is used in making radio and television cabinets, furniture, and chemical containers.

In order to improve the bonding practice, it is necessary for the engineer to be well informed of the fundamental principles involved. A knowledge of the theory of bonding, the nature of the bond, and the factors affecting the bond strength would be helpful in attaining this goal.

The purpose of this investigation was to study the factors affecting the bond strength between polyvinyl chloride sheeting and metal.

The metals used in this investigation were aluminum, brass, copper, nickel, low carbon steel, and stainless steel. The plastic sheeting was bonded to the metal by means of synthetic adhesive. Five different commercial adhesives were used. These were vinyl chloride-acetate resin, VYNW, modified vinyl chloride-acetate resin, VMCH, vinyl acetate resin, A-70, vinyl alcohol-acetate resin, T-24-9, and vinyl alcohol-acetate resin, MA-28-18.

The specimens of metal were treated as follows. Three sets of specimens were prepared. The first set was degreased with solvent only, the second one was polished and degreased, and the third one was degreased and etched. Semi-rigid polyvinyl chloride sheeting was bonded to the metal at a temperature of 70°, 150°, 250°, and 350°F under a pressure of 200 pounds per square inch. A series of the bonded specimens was stretched to 10, 20, and 30 percent elongation. A series of steel-steel laminates was prepared. They were bonded by different adhesives at 250°F under 200 pounds per square inch. The specimens of this series were tested for shear strength.

The effect of surface conditions, of bonding temperatures, of nature of metals, of types of adhesives, and of amount of plasticizer in the adhesive upon the bond strength between polyvinyl chloride sheet and metal was determined and the following conclusions were reached:

1. The bond strength was affected by surface conditions. Etched specimens had higher bond strength than polished ones except low carbon steel.

2. The bonding temperature had no definite influence on the bond strengths of aluminum, nickel, low carbon steel, and stainless steel laminates.

3. The bond strengths of brass and copper laminates increased with the bonding temperature.

4. The average bond strengths of polished specimens of low carbon steel, aluminum, stainless steel, nickel, copper, and brass were 19.6, 15.5, 14.2, 8.5, 5.5, and 2.5 pounds per inch respectively. The strengths of these metal laminates followed the order of these metals in the galvanic series except aluminum.

5. The adhesion between adhesive and metal varied directly with the polarity of the adhesive.

6. The bond strength was also affected by the amount of plasticizer in the adhesive. When the laminates were subjected to stretching, the rate of decrease in strength was inversely proportional to the amount of plasticizer in the adhesive.