Expanded Polystyrene (also Styrofoam), polypropylene, polyethylene, and polyurethane. These two alkenes are precursors to polymers, including polyethylene, polystyrene, acrylates, polypropylene, etc. Acrylonitrile butadiene styrene (ABS) is a material that is stronger than pure polystyrene. Styrene is the precursor to polystyrene and several copolymers. Polarizers are routinely used to detect stress in plastics such as polystyrene and polycarbonate. The highest growth came in the production of plastics, polystyrene, and polypropylene. The state of Maine ban Styrofoam (polystyrene) containers in May 2019. Toy and replica versions made of polystyrene foam or plastic are also available. Mothra's silk was created from a form of liquid styrofoam called "expanded Polystyrene". Due to the low density of polystyrene foam, it is not economical to collect. This may someday be of use in the effective disposing of polystyrene foam. Previous experiments generally used plastic ablators, typically polystyrene (CH). Efforts have been made to find alternatives to polystyrene, especially foam in restaurant settings. The growing chains can add across the double bonds of rubber molecules forming polystyrene branches. Macroscopically, graupel resembles small beads of polystyrene.