Blow molding is a molten tube (called a parison or preform) formed of a thermoplastic material (polymer or resin). The parison or preform is placed in a cavity, which is expanded by compressed air to form a cavity. It is cooled before being taken out of the mold. Nowadays, China Pet Bottle have been loved and trusted by customers all over the world for their excellent quality and suitable price.
Any hollow thermoplastic part can be made into a blow mold. Parts are not limited to bottles, they have only one opening, and their diameter or size is usually smaller than the overall size. These are some of the most common shapes used in consumer packaging, but there are other typical blow moldings.
The basic concept of blow molding comes from the glass blow molding process. As early as the 1880s, there was a patented method for extrusion molding and blow molding of cellophane polymers. Early methods and materials for blow molding plastics were very rough and not suitable for large-scale production. It was not until the late 1930s that the first commercial machines and products were used to produce blow molded bottles. The main event that sparked and drove early commercial blow molding was the development of low-density and high-density polyethylene for blow molding and consumer packaging.
The main difference between blow moulds is the method of forming the parison; the size of the parison and the method of moving between the parison and the blow mould by extrusion or injection molding; whether fixed, shuttle, linear or Rotating.
In an extruded Pet Preform mold (EMM), the polymer melts and the solid extruded melt is extruded through a die to form a hollow tube or parison. The two halves of the cooling mold are then closed around the parison, pressurized air is introduced through the pin or needle, and it expands into a mold shape to form a hollow portion. After the hot plastic is sufficiently cooled, the mold is opened and the parts are taken out.