Extrusion blow molding is a method of manufacturing hollow thermoplastic making parts. The well-known blow molding objects include bottles, buckets, tanks, boxes and containers of all packaged foods, beverages, cosmetics, medicines and daily necessities. Large blown plastic containers are usually used in chemical products, lubricants and packaging of bulk materials. Other blow molding products have balls, bellows and toys. For automobile manufacturing, fuel tank, car shock absorber, seat back, center bracket and armrest and headrest cover are all blown. For machinery and furniture manufacturing, blow molding parts have shells, door frames, frames, ceramic POTS or to an open box.
3/4 of the blow molding products are made by extrusion blow molding.
Extrusion blow molding process consists of 5 steps:
1. Plastic type embryo (extrusion of hollow plastic tube);
2. In the type embryo, the valve is closed, clamped and cut off the mold;
3. Blow up the cold wall of the cavity, adjust the opening and maintain some pressure during cooling.
4. Open the mould and unload the blown parts;
Trim the edges to get the finished product.
Polymer mixing is defined as a process by which a polymer or polymer system can be improved by a mixture of melt. Mixing process from single additive to a variety of additives, polymer alloys and reactive mixtures has a wide range. It is estimated that one-third of all polymer production in the United States is mixed. Mixing ingredients can be customized according to the performance requirements of the final application. Mixing products have mixed performance, such as high gloss and excellent impact strength, or precision moulding and good rigidity.
Mixtures of good polymers are usually used for further processing. However, the growing interest in industry is to combine the mix with the next process, such as extrusion of profiles so as to avoid reheating the polymer.
Various types of melt mixers are used, from the roller mixer and the batch mixer to the single screw and twin screw extruder. Continuous mixing (extruding machine) is the most commonly used equipment, because he can provide products with consistent quality and can reduce operating expenses. There are two types of mixing: distributed mixtures can be evenly distributed without high shear stress in mixing ingredients. This type of mixture is known as extended mixing or laminar mixing.
Distributed mixing is also known as strong mixing, where high shear stress is applied to break up the solid. For example, when the additive mass is broken, the actual particle size becomes smaller.
Mix and match operations often require two types of mixing in a process.