Plastic processes blow molding

Table 4-11. Guide to Processing Temperatures of Plastics for Blow Molding. ...

A. J. Woytek and. E. Gentilecore, "A New Blow Mol ding Process to Reduce Solvent Permeation of Polyolefin Containers," paper no. 13 presented at ddpances in Blow Molding Conference Rubber and Plastics Institute, London, Dec. 6,1977. 

Designers and processors to produce products at the lowest cost have unconsciously used the basic concept of the FALLO approach. This approach makes one aware that many steps are involved to be successful, all of which must be coordinated and interrelated. It starts with the design that involves specifying the plastic, and specifying the manufacturing process. The specific process (injection, extrusion, blow molding, thermoforming, and so forth) is an important part of the overall scheme and should not be problematic. 

Different products are blow molded (Table 8-21). Table 8-22 provides cost data comparing different BM processes with different plastics. 

Important are behaviors associated and interrelated with plastic materials (thermoplastics, thermosets, elastomers, reinforced plastics, etc.) and fabricating processes (extrusion, injection molding, blow molding, forming, foaming, reaction injection molding, etc.). They are presented so that the technical or non-technical reader can readily understand the interrelationships. 

Plasticator A very important component in a melting process is the plasticator with its usual specialty designed screw and barrel used that is used in different machines (extruders, injection molding, blow molding, etc.). If the proper screw design is not used products may not meet or maximize their performance and meet their cost requirements. The hard steel shaft screws have helical flights, which rotates within a barrel to mechanically process and advance (pump) the plastic. There are general purposes and dedicated screws used. The type of screw used is dependent on the plastic material to be processed. 

The rigid plastic milk bottles are made in the dairy processing plant using blow molding. In this process, HDPE pellets are fed from a hopper into an extruder where they are heated by shear and heat to soften them. 

In South Africa, owing to the diversity and small production volume of specific motor car models, it is not economically feasible to blow-mold HDPE fuel tanks. The only cost-effective plastic tank manufacturing process used in South Africa is rotational molding, using LLDPE with a density of 0.939 g/cm3. Some selected properties of LLDPE before and after petrol exposure are compared to HDPE in Table 16.2. It is clear that owing to weaker mechanical properties, LLDPE is far less suitable than HDPE for petrol containment, mainly because of its lower crystallinity. 

Engineers like to design machines that take plastics and inject them into molds, extrude them into filament, sheets, rods, and film, or blow-mold them into shapes. They want these plastics to have a terrific balance of mechanical, electrical, and chemical properties. That s why they have attached their name to engineering resins, a set of plastics unlike thermosets that they can remelt and further process mechanically. Nylon, polycarbonates, and polyesters are the three most popular engineering resins. 

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