Coating Procedures for Plastisol CoatingsComments Off on Coating Procedures for Plastisol Coatings
Plastisol coatings are applied to many different products in order to supply them with aesthetic qualities, tactile softness and gripping power. For instance, tools like pliers and screwdrivers are often fitted with plastisol coatings on their handles in order to provide the user with a solid grip instead of sheer metal. Plastisol coatings involve a plasticized resin combined with many PVC particles, which provide the plastisol with increased durability, toughness and thickness. In order to stay affixed to substrates, plastisol must be combined with a primer, which connects the plastisol particles to the substrate. Different kinds of primers are used depending on the adhesion coating method and the intended result. The plastisol itself has many desirable features, including chemical resistance to acids, alkalines, detergents, oils and certain solvents. Plastisol coatings also maintain structural integrity to – 65 degrees Fahrenheit and provide extraction resistance to different oils and detergents. A plastisol coating can perform well for approximately ten years. Plastisol mixtures can be varied to allow differences in gloss, thickness, toughness and other physical properties.
There are many types of coating procedures that work well with plastisols, most all of which involve heating (curing) the substrate and plastisol resin and a cooling period. These different plastisol coating procedures yield a variety of results and differences in the thickness, texture and geometry of the coating. Some coatings are directly applied to a substrate while others are made in molds.
Dip molding is accomplished in either a hot or cold dip process. In hot dip molding, the substrate is heated and the plastisol resin is heated until bubbles appear, as if it were boiling. The substrate is then slowly dipped straight into the liquid plastisol and then removed slightly faster so the entire piece is coated in plastisol. Cold dip molding is used when the substrate cannot undergo heating, such as in the case of a wooden or fabric substrate, and it is simply dipped into the heated plastisol resin as is. After the dipping procedure, both hot and cold dip molding require the substrate be briefly “cured,” or heated until the plastisol achieves a solid state.
Slush molding is similar to dip molding but involves an extra step to ensure complete coating of a substrate. The process is generally used in cases where the substrate has a complex geometry and includes nooks and crannies that may be difficult to coat by simply dipping the piece into the plastisol resin. Following the dipping procedure, a substrate undergoes slush molding by being affixed into a centrifuge that spins very quickly. This spinning process ensures that the resin fills in all the parts of the substrate. The substrate is then cured and the resin solidifies as in dip molding.
Rotational molding is used to make products that are hollow, such as buoys and balls. A mold of the product is filled with heated resin, and then the mold rotates at slow speed, allowing the liquid within to slowly coat the entirety of the mold. The plastisol eventually solidifies in the shape of the mold.
Casting is similar to rotational molding but does not involve the movement. When a product with a complex geometry needs to be coating in plastisol, a mold can be made of the shape of plastisol needed. The heated plastisol liquid is then poured into the mold and heated until it solidifies. Once it solidifies, the plastisol mold acts as a sleeve for the product, and can be affixed to the substrate with a small amount of adhesive.
Spray coating is used to apply a very thin film coating of plastisol to a substrate. The substrate is sprayed with heated liquid plastisol by a gun, and then heated to allow the plastisol to solidify.
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