The main blow molding apparatus comprising: injection machine parison mold and demolding apparatus. Structure 

(1) injection molding machine and preform injection molding machine in general the same, but a lower injection pressure, screw length may be smaller, the compression ratio is not too large. 

(2) including injection mold and blow mold mold. Injection mold the parison injection mold and the general requirements of the same materials and processing, the mandrel must be hollow to pass into the air. And extrusion blow molds - blow mold basically the same.

 (3) stripping device and extrusion - blow molding different, after the blow molding process is complete, open the blow mold, the molded article with a mandrel to the stripping unit, the stripper plate and mandrel to separate the products. Product standard injection - blow molding of plastic bottles is currently no national standard and the Ministry of standard, product standards can refer to a standard polyethylene blown barrels, and make the necessary corrections. But the same kind of raw NOTE - Blow container than crowded - Blow excellent container properties. Generally refers to the large volume of hollow container 50L cooper body over a variety of plastic, tank, tank, tank and other large hollow products. Polyethylene resin-based raw materials, primarily for extrusion molding - blow molding and rotational molding. Extrusion - blow molding of large containers and plastic buckets basically the same method, only a slight difference in terms of materials and equipment. The main raw materials are generally required to produce plastic bucket or high density polyethylene resins, low density polyethylene-based resin mixture, and the production of large containers either high-density polyethylene and high molecular weight polyethylene-based resin. The main characteristics of the production equipment and a large container of extruders and blow molding equipment and the production of plastic barrels are the same device, but it should be between the creation of the extruder barrel and head hopper, see Figure 8 - 7. Because large products parison also great, if slowly extruded from the extruder, the parison serious drawdown phenomenon occurs due to the weight, resulting in products uneven vertical wall thickness. Extruding the same time because a long time, by cooling the parison temperature is too low, will also affect the quality of the blow. After the addition of the hopper means, the continuous extruder squeeze molten material stocker, when stored for a certain amount of material, a material that is quickly pushed out by the pressure device to form a uniform thickness, the temperature of the parison appropriate . So not only can reduce the additional hopper drawdown parison maintain parison temperature, but also with a smaller extruder producing large products. 

(A) a suitable stretching temperature is a temperature controlled stretching biaxially stretched key, that otherwise would not achieve the purpose of re-orientation of the plastic molecules. Non-crystalline polyvinyl chloride is such as one-step, from the parison to 190 ℃ ~ 200 ℃ extrusion is then cooled preferably to 90 ℃ ~ 100 ℃, and stretch blow molding. Then 10 ℃ ~ 20 ℃ higher than its glass transition temperature, is the best stretch temperature. Of crystalline polypropylenes, such as one-step, by means of the parison to be effectively cooled. From the time of extrusion 210 ℃ ~ 230 ℃ rapidly cooled to the crystallization temperature between 90 ℃ ~ 105 ℃, inhibit the formation of spherulites, and then heated to the glass transition temperature and the melting temperature between 150 ℃ ~ 160 ℃ double axis stretching. Whether polypropylene or polyvinyl chloride, if the two-step, all need to be made in advance to the respective reheated preform stretching temperature, and then stretch blow molding. 

(2) except that the draw ratio stretching conditions such as temperature, the molecular alignment state of the biaxially stretched product is determined by the draw ratio, and thus determines the stretch ratio to improve product performance. Stretch ratio and the stretching ratio is the product of the blow ratio, and the stretch ratio is the length of the article than the length of the parison, which is the longitudinal stretch ratio. The blow up ratio is the maximum diameter larger than the diameter of the preform article, which is the radial stretch ratio. Stretching ratio is too low, would not achieve the role of molecular reorientation and improve product performance. Stretching ratio is too high, it will cause material damage blanks and make processing conditions difficult to control. PVC stretch ratio generally take 4 to 6, and polypropylene taken 6 to 10.