Polyresin is a compound used for making statues, figurines, and decorative furniture. It is sturdy and can be molded intricately. As a result, it allows a great level of detail with consistent texture. It is of two types in general namely, Polyester resin and Synthetic resin.
Polyester resins are unsaturated resins used in molding a compound. These fiber glass compounds are used in restaurants, kitchens, restrooms and other areas that require washable walls but serve the display purpose.
Synthetic resins are hard and comprises of viscous liquids which can be categorized into several classes. These are copolymers or thermosetting plastics, prepared by the process of esterification.
Epoxy resin is the basic class of synthetic resins which is stronger than concrete, seamless and waterproof. Another similar class is acetal resin and it is not as complex as epoxy resin.
Another class of synthetic resins is Ion exchange resins which is widely used in water purification and catalytic process of organic substances.
Unsaturated polyester resins is the most commonly used class of resins with composition of more than 75% of resins.
The procedure followed in casting resin is summarized below. Resin casting is a method of plastic casting. First a mold is created that is filled with liquid synthetic resin, which then hardens. These are used in the production of collectible toys, models and figures, as well as small-scale jewelry production.
The process involves the transformation of the liquid monomer into a polymer which occurs on hardening of the solid.
Acrylic glass which is commonly used for framing photos and other display purpose is not a glass but rather a plastic polymer that is transparent, and very hard.
But the simplest method in resin casting is gravity casting method. Here the resin is poured into the mold and pulled down into all the parts by gravity. The action of vacuum is essential here are it helps to expel bubbles and any air gaps between them. These kind of compounds are highly priced due to the amount of hands-on labor involved in the final stage.
Polyresins are used in the production of customized toys and figures as well as scale models. They are generally produced in small quantities, from the tens to a few hundred copies, compared to injection-molded plastic figures which are produced in many thousands. Resin casting is more labor intensive than injection molding.
The traditional sculpting process is first employed in the creation of mold. After the mold has been made, a synthetic resin mixed with a curing agent, is poured into it. Within minutes the material hardens, yielding castings or copies in the shape of the mold into which it has been poured. The hardened resin casting is removed from the flexible mold and allowed to cool.
Due to aggressive nature of most compounds used for casting and the high temperature of the reaction the mold gradually degrades and loses small details. The sprues and seams are then sanded or cut by free hand and the small details are craved and polished.
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