The best glues for adhering hard plastic materials are polystyrene cement and cyanoacrylate, also known as instant glue or superglue. Some glues have been specifically designed for particular plastics, such as polypropylene, acrylics and polyvinyl chloride.
When gluing plastics together, the surfaces should be clean and dry. In some cases it may be necessary to roughen up the surfaces with fine-grade sandpaper to achieve the strongest bond. Similarly, if gluing plastic joints, a beveled or slightly rounded edge may help.
After gluing them together, it is important to leave the pieces to dry for the length of time recommended by the glue instructions. For the best results, hold glued pieces together with clamps, tape or rubber bands, or, if flat, place under heavy books.