Polymer Siding. This kind of siding is made from polypropylene resin. The typical application for this kind of siding is Shake and Shingle cladding with a cedar pattern which can be used as a whole house application or in accent areas. Polymer siding utilizes an injection molding process that enables the final product to have a highly defined three-dimensional pattern in a variety of styles, sizes and colors. The product mold is precisely shaped to give it the exact dimensions needed and it incorporates any other necessary configurational details, such as ribbing on the back for extra stability. The molten compound is injected into the mold, which is itself heated to a high temperature. Upon completion of this step the piece is finished, and all that remains is for it to cool down. Injection molded siding began to enter the market in the mid 1990s and has grown steadily in popularity ever since as processes have been improved, styles have been enhanced and colors increased. CertainTeed offers six types of polymer siding under our Cedar Impressions® product category. Cedar Impressions include perfections shingles, rough-split shakes and half-round shingles to round out a complete offering. These distinctive polymer siding panels are available in up to 31 low-gloss colors with a wide variety of coordinating trim.