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What is Plastisol?

M. Walker
M. Walker

Plastisol is a compound made from various resins mixed with plasticizers, which are designed to increase the fluidity of the resins. The resin is usually made out of particles of polyvinyl chloride (PVC), a plastic polymer that contains a series of vinyl groups, or carbon-carbon double bond units. Upon mixing the particles with the plasticizer, the compound can be heated, dissolved, and molded. Applications of plastisol include molding, casting, textile inks, and screen-printing.

Since the plasticizer is able to increase the elasticity of the vinyl polymer, the two can form a liquid upon heating. Plastisol is fully dissolved and mixed at a temperature of 350.6°F (about 177°C), at which point it can be placed into a mold to cool. Once the temperature reaches below 140°F (about 60°C), the plastic has set and formed a solid, flexible object. In addition to PVC resins other plastics can be added, but plastisol will still remain a completely solid compound upon curing.

Man with a drill
Man with a drill

This molding practice makes plastisol a good candidate for slush molding and casting, processes used to create detailed molded products. The liquid plastic compound is inserted into a metal mold, which is then spun at high speeds. Spinning utilizes centripetal force to press the liquid into the smaller spaces of the mold and ensure even contact throughout. Once spun, the mold can be heated to cure the material, as metal molds are not negatively affected by heat in the same way as more flexible resin molds. Slush molding is generally considered to create more complex molds than simpler spin casting practices, but it is less detailed and less costly than plastic injection molding techniques.

Plastisol is also commonly used for screen-printing and textile inks because it is not water-soluble and does not require a washing process after printing. The compound is also considered relatively safe and has a health hazard rating of one, indicating that it is only slightly hazardous. Flammability and reactivity are also low, as are potentially harmful solvents within the plastic mixture and the presence of volatile organic compounds (VOCs).

The main requirements of screen-printed fabrics are that they can withstand the heat needed to cure the plastisol inks and that they can provide a porous enough surface for the compound to bind. Unlike dyes, plastic textile inks do not become absorbed by the fibers in fabrics. Instead, they bond to the fibers and form a coating around them, which is why a porous surface is necessary for a strong hold.

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