Extrusion blow molding of plastic mold

Well-known blow molding objects are bottles, buckets, cans, boxes, and all the containers that contain food, beverages, cosmetics, medicines, and daily necessities. Large blow molded containers are commonly used for packaging chemicals, lubricants and bulk materials. Other blow molding products include balls, bellows and toys. For the automotive industry, fuel tanks, car shock absorbers, seat backs, center brackets, and armrest and headrest coverings are all blow molded. For machinery and furniture manufacturing, blow molded parts are shells, door frames, frames, clay POTS, or boxes with an open face. Extrusion blow molding is a method of making hollow thermoplastic parts.

Polymer

Ordinary blow molding extrusion plastic raw material is high density polyethylene, blow molding processing most of the milk usually has this polymer made. Other polyolefins are often processed by blow molding. Depending on the use, styrene polymers, polyvinyl chloride, polyester, polyurethane, polycarbonate and other thermoplastics can also be used for blow molding.

Engineering plastics are widely accepted in the automotive industry. The selection of blow molding processing materials is based on mechanical strength, weather resistance, electrical properties, optical properties and other properties.

Material mix

Various types of melt mixing equipment are used, from roller mills and batch mixers to single - and twin-screw extruders. Continuous mixing (extruder) is commonly used equipment because it provides a consistent quality product and reduces operating costs. 

There are two mixed types:

Distributed mixtures can be evenly distributed without high shear stress in remixing. Such mixtures are called extensional or laminar mixtures.

Dispersed mixing, also known as strong mixing, in which high shear stresses are applied to break up clumped solids. For example, when the additive pellet is broken, the actual particle size is reduced.

Mixing operations often require two mixing types in one process.

Process

3/4 of blow molding products are made by extrusion blow molding. Extrusion is the process of forcing material through a hole or mold to make a product.

Extrusion blow molding process consists of 5 steps: 

1. plastic embryo (hollow plastic tube extrusion); 

2. Close the flap mold on the mold, clamp the mold, and cut off the mold; 

3. Blow to the cold wall of the mold cavity, adjust the opening and maintain a certain pressure during the cooling period, 

4.open the mold, and write down the blown parts; 

5. Trim the flaps to get the finished product.

Extruded

Polymer mixing is defined as the process of upgrading a polymer or polymer system through melt mixing. The mixing process ranges from the addition of a single additive to the treatment of multiple additives, polymer alloys and reactive mixing. It is estimated that a third of all polymer production in the United States goes through blending. The mix can be customized according to the performance requirements of the final application. Hybrid products have hybrid properties, such as high gloss and excellent impact resistance, or precision molding and good stiffness.

The mixed polymer is usually pelleted for further processing. However, industry is increasingly interested in combining mixing with a further process, such as profile extrusion, to avoid reheating the polymer.